The GNU Pascal Manual

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GNU Pascal

This manual documents how to run, install and maintain the GNU Pascal Compiler (GPC), as well as its new features and incompatibilities, and how to report bugs. It corresponds to GPC 20040516 (GCC 2.8.1, 2.95.x or 3.2.x).

Introduction:

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Welcome to GNU Pascal ...

... the free 32/64-bit Pascal compiler of the GNU Compiler Collection (GNU CC or GCC). It combines a Pascal front-end with the proven GCC back-end for code generation and optimization. Other compilers in the collection currently include compilers for the Ada, C, C++, Objective C, Chill, FORTRAN, and Java languages. Unlike utilities such as p2c, this is a true compiler, not just a converter.

This version of GPC corresponds to GCC version 2.8.1, 2.95.x or 3.2.x.

The purpose of the GNU Pascal project is to produce a Pascal compiler (called GNU Pascal or GPC) which

Pascal was originally designed for teaching. GNU Pascal provides a smooth way to proceed to challenging programming tasks without learning a completely different language.

The current release implements Standard Pascal (ISO 7185, levels 0 and 1), most of Extended Pascal (ISO 10206, aiming for full compliance), is highly compatible to Borland Pascal (version 7.0), has some features for compatibility to other compilers (such as VAX Pascal, Sun Pascal, Mac Pascal, Borland Delphi and Pascal-SC).

It provides a lot of useful GNU extensions not found in other Pascal compilers, e.g. to ease the interfacing with C and other languages in a portable way, and to work with files, directories, dates and more, mostly independent of the underlying operating system.

Included units provide support for regular expressions, arithmetic with integer, rational and real numbers of unlimited size, internationalization, inter-process communication, message digests and more. Demo programs show the usage of these units and of many compiler features.

This manual contains

If you are familiar with Standard Pascal (ISO 7185) programming, you can probably just go ahead and try to compile your programs. Also, most of the ISO Extended Pascal Standard (ISO 10206) is implemented into GNU Pascal. The Extended Pascal features still missing from GPC are qualified module import, protected module export variables, set types with variable bounds, structured value initializers and expressions as subrange lower bounds.

If you are a Borland Pascal programmer, you should probably start reading the QuickStart guide from BP to GNU Pascal, see Borland Pascal. If you are curious about the new features GPC offers, you can get an idea in the overview of GPC highlights (see Highlights), and read in more detail about them in the Programmer's Guide to GPC (see Programming) and in the alphabetical GPC Language Reference (see Reference).

And, please, think about how you can contribute to the GNU Pascal project, too. Please support our work by contributing yours in form of example programs, bug reports, documentation, or even actual improvements of the compiler.

All trademarks used in this manual are properties of their respective owners.

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1 Some of GPC's most interesting features.

The GNU Pascal Compiler (GPC) is, as the name says, the Pascal compiler of the GNU family (http://www.gnu.org/software/gcc/). This means:

The compiler supports the following language standards and quasi-standards:

Some highlights:

The demo programs mentioned above are available both on the WWW and in GPC source and binary distributions.

Disadvantages:

Co-workers welcome!

Able, committed programmers are always welcome in the GNU Pascal team. If you want to be independent of companies that you have to pay in order to get a compiler with more restrictive licensing conditions that only runs on one operating system, be invited to join the development team, Acknowledgments.

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2 New Features of GNU Pascal.

GPC's new or changed features since the last (non alpha/beta) GPC release are listed here. Items without further description refer to new routines, variables or options.

Features implemented for compatibility to other compilers are marked with, e.g., (B) for BP compatibility.

A few old and obsolete features have been dropped or replaced by cleaner, more flexible or otherwise more useful ones. This might lead to minor problems with old code, but we suppose they're rare and easy to overcome. Backward-incompatible changes are marked with (@).

Have fun,

The GNU Pascal Development Team

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3 The GNU Pascal Frequently Asked Questions List.

This is the Frequently Asked Questions List (FAQ) for GNU Pascal. If the FAQ and the documentation do not help you, you have detected a bug in it which should be reported, Mailing List. Please really do it, so we can improve the documentation.

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3.1 GNU Pascal

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3.1.1 What and why?

The purpose of the GNU Pascal project is to produce a Pascal compiler (called GNU Pascal or GPC) which

Pascal was originally designed for teaching. GNU Pascal provides a smooth way to proceed to challenging programming tasks without learning a completely different language.

The current release implements Standard Pascal (ISO 7185, levels 0 and 1), most of Extended Pascal (ISO 10206, aiming for full compliance), is highly compatible to Borland Pascal (version 7.0), has some features for compatibility to other compilers (such as VAX Pascal, Sun Pascal, Mac Pascal, Borland Delphi and Pascal-SC).

It provides a lot of useful GNU extensions not found in other Pascal compilers, e.g. to ease the interfacing with C and other languages in a portable way, and to work with files, directories, dates and more, mostly independent of the underlying operating system.

Included units provide support for regular expressions, arithmetic with integer, rational and real numbers of unlimited size, internationalization, inter-process communication, message digests and more. Demo programs show the usage of these units and of many compiler features.

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3.1.2 What is the current version?

Prior to July 2000 releases were several months apart. Since then there has been a new release every few days, available as a source archive from the GPC web site, http://www.gnu-pascal.de.

For details about new features, see the section News on the web site. On bugs fixed recently, see the Done section of the To-Do list (on the same web site).

GPC uses GCC as a back-end. Patches for GCC 2.8.1 and GCC 2.95.x are provided but it is recommended that you use GCC 2.95.x.

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3.1.3 Is it compatible with Turbo Pascal (R)?

GPC is not a drop-in replacement for Borland's Turbo Pascal (R). Almost all BP language features are supported. Notable exceptions are the string format (as discussed below), or the Mem and Port pseudo arrays, though replacement functions for the latter on IA32 platforms exist in the Ports unit.

Almost all of BP's run time library is supported in GPC, either by built-in compiler features or in units with the same names as their BP counterparts.

For details about the compatibility, the few remaining incompatibilities and some useful alternatives to BP features, see the Borland Pascal chapter in the GPC Manual. (see Borland Pascal)

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3.1.4 Which platforms are supported by GNU Pascal?

GPC uses the GCC backend, so it should run on any system that is supported by GNU CC. This includes a large variety of Unix systems, MS-DOS, OS/2 and Win32. A full list of platforms supported by GCC can be found in the file INSTALL of the GCC distribution. Not all of these have actually been tested, but it is known to run on these platforms:

ix86-gnu (GNU Hurd)
ix86-linux (Linux 2.x, ELF)
i486-linuxaout
i486-linuxoldld
i386-freebsd1.2.0
AIX 4.2.1
AIX 4.3
DJGPP V2 (Dos)
EMX 0.9B (OS/2, Dos)
Cygwin32 beta20 and higher (MS-Windows95/98, MS-Windows NT)
mingw32 (MS-Windows95/98, MS-Windows NT)
MSYS (MS-Windows)
mips-sgi-irix5.3
mips-sgi-irix6.5
sun-sparc-sunos4.1.4
sparc-sun-solaris2.x
sun-sparc-solaris 2.5.1
sun-sparc-solaris 2.6
sun-sparc-solaris 7
sun-sparc-solaris 8
alpha-unknown-linux
alpha-dec-osf4.0b
s390-ibm-linux-gnu

OK people - send us your success stories, with canonical machine name!

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3.2 Installing GPC

You find the most up-to-date installation instructions in the GPC Manual or the file INSTALL in source distributions, or on the GPC web site. (see Installation)

The following sections describe things you might need or want to install besides GPC itself.

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3.2.1 What to read next

After installing GPC, please check the files in the directory /usr/local/doc/gpc:

README General Information about GPC
FAQ This FAQ :-)
NEWS Changes since the last release
BUGS How to report bugs, about the Test Suite
AUTHORS List of GPC authors
COPYING The GNU General Public License
COPYING.LIB The GNU Lesser General Public License

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3.2.2 Which components do I need to compile Pascal code?

A complete Pascal compiler system should at least have:

  1. The actual compiler, GPC.
  2. An editor, assembler, linker, librarian and friends.
  3. A C library. If you have a working C compiler, you already have this.
  4. A debugger, if you want to debug your programs.

For most people, the GNU binutils and GNU debugger (gdb) are a good choice, although some may prefer to use vendor specific tools.

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3.2.3 How do I debug my Pascal programs?

To debug your programs, (a) GNU Pascal must be able to generate executables with debug info for your platform, and (b) you must have a debugger which understands this.

The bottom line: if you can debug GCC compiled programs, you should be able to do this with GPC too.

The GNU debugger (gdb) currently does not have a "Pascal" mode, so it is unable to display certain Pascal structures etc. When debugging, please note that the Initial Letter In Each Identifier Is In Upper Case And The Rest Are In Lower Case. If you want to display variable foo in the debugger, type show Foo or display Foo instead.

Although gdb is an excellent debugger, it's user interface is not everybody's preference. If you like to debug under X11, please refer to the comp.windows.x FAQ: "Where can I get an X-based debugger?" at:
http://www.cis.ohio-state.edu/hypertext/faq/usenet/x-faq/part6/faq-doc-2.html

Some useful frontends include: XXGDB, tGDB and XWPE. See:
http://www.ee.ryerson.ca:8080/~elf/xapps/Q-IV.html

Very nice, but resource consuming is the Motif based DDD:
http://sol.ibr.cs.tu-bs.de/softech/ddd/

Furthermore, RHIDE (see IDE) contains built-in debugging suport, similar to the IDE of BP.

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3.2.4 What additional libraries should I have?

You will need certain additional libraries when you compile some of the units. These can be found in the directory http://www.gnu-pascal.de/libs/.

Currently, there are the following libraries:

gmp
Arithmetic for integers, rationals and real numbers with arbitrary size and precision. Used by the GMP unit.
rx
Regular expression matching and substitution. Used by the RegEx unit.
ncurses
PDCurses
Screen handling. Used by the CRT unit. Depending on your system, you have the following choices:

Unix: You can compile terminal applications with ncurses and applications that run in an X11 window with PDCurses (though terminal applications can, of course, also run in an xterm under X11). ncurses is used by default. If you want to use PDCurses (a.k.a. XCurses), give the option -DX11 when compiling CRT.

Dos with DJGPP and MS-Windows with mingw: Only PDCurses is available and will be used by default.

MS-Windows with Cygwin: PDCurses and ncurses are available. PDCurses is used by default. If you want to use ncurses, give the option -DUSE_NCURSES when compiling CRT.

Other systems: Please see the READMEs and installation instructions of PDCurses and ncurses to find out which one(s) can be built on your system. See the conditionals at the end of crt.inc and crtc.h (and change them if necessary) on which library is used by default.

intl
Internationalization. Used by the Intl unit. On some systems, it is part of the system library (libc).
ElectricFence
This library is not used by any GPC unit. It is a debugging tool to assist you in finding memory allocation bugs. To use it, just link it to your program, either on the command line (-lefence) or in the source code ({$L efence}) which you might want to put into an {$ifdef DEBUG} or similar since using libefence is only recommended for debugging.

The source code of the libraries is available in the main libs directory. Most libraries come with one or several patches which should be applied before compiling them.

Binaries for some platforms are available in the binary/platform subdirectories. If you compile the libraries for other platforms, be invited to make the binaries available to us for distribution on the web site.

There are also the following files:

terminfo-linux.tar.gz
This is a patch to enable ncurses programs to make use of the ability of Linux 2.2 and newer kernels to produce a block cursor when needed. The present patch can be installed without recompiling anything, just by copying some files into place. More details can be found in the README file included in this archive. The patch will not do any harm on older kernels. Please note that not only on Linux machines it is useful to install the patch. Installing them on any other machine will allow users who telnet in from a Linux console to profit from the block cursor capability. Besides, some Unix systems have installed older Linux terminfo entries or none at all, so it's a good thing, anyway, to give them a current version. The patch is included in the terminfo database of ncurses 5.0, so if you install ncurses 5.0 (source or binary), you don't need to get the patch separately. But you can install it on a system with an older ncurses version if you don't feel like upgrading ncurses altogether.
tsort-2.9i.zip
A little utility (extracted from util-linux-2.9i, but not Linux specific), needed for the configuration of the rx library. You need it only if you compile rx yourself (and if it's not already present on your system), not when using a rx binary.

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3.2.5 Contributed units

Several people have contributed units for GPC. They are usually announced on the mailing list, Mailing List. Most of them can be found in http://www.gnu-pascal.de/contrib/.

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3.2.6 Can you recommend an IDE?

Users of Borland Pascal may wonder if there's a replacement for the IDE (Integrated Development Environment). Here's a few suggestions:

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3.3 GNU Pascal on the DJGPP (MS-DOS) platform

This chapter discusses some potential problems with GNU Pascal on MS-DOS, using DJGPP.

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3.3.1 What is DJGPP?

The following paragraph is from the site http://www.delorie.com/djgpp/:

DJGPP is a complete 32-bit C/C++ development system for Intel 80386 (and higher) PCs running DOS. It includes ports of many GNU development utilities. The development tools require a 80386 or newer computer to run, as do the programs they produce. In most cases, the programs it produces can be sold commercially without license or royalties.

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3.3.2 If you need more information

GPC/DJGPP is a DJGPP V2 application, and most of the DJGPP documentation applies for GPC too. A great source of information is the DJGPP FAQ: http://www.delorie.com/djgpp/v2faq/230b.zip

Another place to look for DJGPP documentation is the DJGPP Knowledge Base, at this URL: http://www.delorie.com/djgpp/doc/kb/

Node: DJGPP download, Next: , Previous: DJGPP FAQ, Up: GPC on DJGPP

3.3.3 What do I download?

As discussed in Components, other than GPC itself, you need an assembler, linker and friends, a C library and possibly a debugger. The site http://www.delorie.com/djgpp/ recommended the following files and they will help you find a mirror:

v2/djdev203.zip (C library)
v2gnu/bnu2951b.zip (assembler, ...)
v2gnu/gcc2952b.zip (gcc)
v2gnu/gdb418b.zip (debugger)
v2gnu/mak379b.zip (make)
v2gnu/txi40b.zip (texi)

This list is about 10 MB not counting GPC. You can use a binary version of GPC from the web site.

Node: Installing GPC on DJGPP, Next: , Previous: DJGPP download, Up: GPC on DJGPP

3.3.4 How do I install the compiler?

If you don't have DJGPP installed on your harddisk, create a directory for GNU Pascal (c:\gpc), and unzip the archives. Make sure you preserve the directory structure (use pkunzip -d). Now, add the directory where gpc.exe lives (c:\gpc\bin) to your path and set the DJGPP environment variable to point to your djgpp.env file: 

     set DJGPP=c:\gpc\djgpp.env

Then, add this to your djgpp.env file: 

     ---------------------------------------------------------
     [gpcpp]
     C_INCLUDE_PATH=%/>;C_INCLUDE_PATH%%DJDIR%/lang/pascal;%DJDIR%/include
     
     [gpc]
     COMPILER_PATH=%/>;COMPILER_PATH%%DJDIR%/bin
     LIBRARY_PATH=%/>;LIBRARY_PATH%%DJDIR%/lib;%DJDIR%/contrib/grx20/lib
     ---------------------------------------------------------

The GPC online documentation is in GNU info format; you need the Info reader (txi390b.zip) to read it, or use the built-in Info reader of the RHIDE or PENG IDE. To add the GPC documentation to the info directory file, edit the c:\gpc\info\dir file, and locate this section: 

     ---------------------------------------------------------
     * GCC: (gcc.inf).
     The GNU C, C++, and Objective-C Compiler
     
     * GDB: (gdb.inf).
     The GNU Debugger (gdb and gdb-dpmi).
     
     ---------------------------------------------------------

To add GPC, change it to look like this: 

     ---------------------------------------------------------
     * GCC: (gcc.inf).
     The GNU C, C++, and Objective-C Compiler
     
     * GPC: (gpc.inf).
     The GNU Pascal Compiler
     
     * GDB: (gdb.inf).
     The GNU Debugger (gdb and gdb-dpmi).
     
     ---------------------------------------------------------

Specific information for low-memory conditions and more can be found in the DJGPP FAQ and documentation.

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3.3.5 I cannot read the Info documentation!

To read the Info documentation, you need the info program from txi390b.zip or an IDE like RHIDE or PENG.

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3.3.6 GPC says: no DPMI

You don't have a DPMI server installed, and DJGPP v2 requires it to run. You can either use one of the commercial DPMI servers (e.g., run gpc in a DOS box under MS-Windows) or download and install CWSDPMI (csdpmi3b.zip) which is a free DPMI server written for DJGPP.

Node: Assembler syntax, Next: , Previous: DJGPP DPMI server, Up: GPC on DJGPP

3.3.7 I have troubles with assembly code

The GNU Assembler (as.exe), or gas, called by GCC accepts "AT&T" syntax which is different from "Intel" syntax. Differences are discussed in section 17.1 of the DJGPP FAQ.

A guide is available which was written by Brennan Mr. Wacko Underwood brennan@mack.rt66.com and describes how to use inline assembly programming with DJGPP, at this URL: http://www.delorie.com/djgpp/doc/brennan/brennan_att_inline_djgpp.html

There's also a GPC assembler tutorial at
http://www.gnu-pascal.de/contrib/misc/gpcasm.zip

Section 17.3 of the DJGPP FAQ discusses some methods to convert "Intel" syntax to "AT&T" syntax.

However, please note that assembler code is unportable, i.e. it will work on IA32 ("x86") and compatible processors if written for them, but will not even compile for other processors. So by writing assembler code in your programs, you will limit their usefulness substantially.

If you think you "need" assembler code for speed - and you've checked that your assembler code actually runs faster than Pascal code compiled with suitable optimizations - you might want to put both Pascal and assembler versions of the critical sections in your program, and let, e.g., an {$ifdef i386} decide which one to use. This way, your program will at least compile on all processors.

Node: DJGPP specific code, Next: , Previous: Assembler syntax, Up: GPC on DJGPP

3.3.8 Tell me how to do DPMI, BIOS and other DOS related things.

DPMI, BIOS and other functions are no different than other system functions. Refer to the GPC Manual on how to access your system's C-library. This small example shows how to use DPMI, copying some structures and function prototypes of <dpmi.h>: 

     program DPMIDemo;
     
     { Only for DJGPP }
     
     {$X+}
     
     { `Byte' is `unsigned char' in C,
       `ShortCard' is `unsigned short' in C,
       `MedCard' is `unsigned long' in C,
       `Word' is `unsigned' in C,
       etc. (all these types are built-in). }
     
     type
       TDpmiVersionRet = record
         Major     : Byte;
         Minor     : Byte;
         Flags     : ShortCard;
         CPU       : Byte;
         Master_PIC: Byte;
         Slave_PIC : Byte;
       end;
     
     type
       TDpmiFreeMemInfo = record
         LargestAvailableFreeBlockInBytes,
         MaximumUnlockedPageAllocationInPages,
         MaximumLockedPageAllocationInPages,
         LinearAddressSpaceSizeInPages,
         TotalNumberOfUnlockedPages,
         TotalNumberOfFreePages,
         TotalNumberOfPhysicalPages,
         FreeLinearAddressSpaceInPages,
         SizeOfPagingFilePartitionInPages,
         Reserved1,
         Reserved2,
         Reserved3: MedCard;
       end;
     
     function DpmiGetVersion (var Version: TDpmiVersionRet): Integer;
              external name '__dpmi_get_version';
     
     function DpmiGetFreeMemoryInformation
              (var MemInfo: TDpmiFreeMemInfo): Integer;
              external name '__dpmi_get_free_memory_information';
     
     var
       Version: TDpmiVersionRet;
       MemInfo: TDpmiFreeMemInfo;
     
     begin
       if DpmiGetVersion (Version) = 0 then
         begin
           WriteLn ('CPU type:       ', Version.CPU, '86');
           WriteLn ('DPMI major:       ', Version.Major);
           WriteLn ('DPMI minor:       ', Version.Minor);
         end
       else
         WriteLn ('Error in DpmiGetVersion');
       if DpmiGetFreeMemoryInformation (MemInfo) = 0 then
         WriteLn ('Free DPMI memory: ',
                  MemInfo.TotalNumberOfFreePages, ' pages.')
       else
         WriteLn ('Error in DpmiGetMemoryInformation');
     end.

Node: Stack size, Previous: DJGPP specific code, Up: GPC on DJGPP

3.3.9 I got an exception when accessing an array [1 .. 4000000] of Byte.

Per default, the maximum stack size of a DJGPP application is 256K. If you need more, you have to adjust it with the stubedit program, i.e.: 

     stubedit your_app.exe minstack=5000K

Another way is to add the following code to your program to define a minimum stack size (here: 2 MB). This value will be honored even if a user sets a lower value by using stubedit, so this method might be a little safer. (The linker name _stklen is essential; the Pascal identifier doesn't matter. The constant doesn't have to be used anywhere in the program. It is recommended to put this declaration in the main program file, not in any unit/module, so programs using a unit/module can set whatever limit they need.) 

     {$ifdef __GO32__}
     const
       MinStackSize: Cardinal = $200000; attribute (name = '_stklen');
     {$endif}

Still, it might be a good idea to use pointers for large structures, and allocate the memory at runtime.

DJGPP has to allocate the stack in physical memory at program startup, so one might have to be careful with too large stack limits. Most other systems allocate stack pages on demand, so the only reason to set a limit at all might be to prevent a runaway recursion from eating up all memory ...

On Unix-like systems, you can set a resource limit, but you usually don't do it in normal programs, but rather in the shell settings (bash: ulimit; csh: limit; syscall: setrlimit(2)).

Node: Strings in GPC, Next: , Previous: GPC on DJGPP, Up: FAQ

3.4 Strings

Node: String schema, Next: , Up: Strings in GPC

3.4.1 What's this confusion about strings?

Turbo Pascal strings have a length byte in front. Since a byte has the range 0 .. 255, this limits a string to 255 characters. However, the Pascal string schema, as defined in section 6.4.3.3.3 of the ISO 10206 Extended Pascal standard, is a schema record: 

     type
       String (Capacity: Integer) = record
         Length: 0 .. Capacity;
         String: packed array [1 .. Capacity + 1] of Char
       end;

The + 1 is a GPC extension to make it feasible to automatically add the #0 terminator when passing or assigning them to CStrings. Thus at the expense of a little added complexity (must declare capacity, don't use GetMem without explicit initialization of the Capacity field, and the additional space requirement) you can now have very long strings.

Node: Strings in variant records, Next: , Previous: String schema, Up: Strings in GPC

3.4.2 Overlaying strings in variant records

Q: Should the different variants in a variant record overlay in the same memory? Previous Pascals I have used have guaranteed this, and I've got low-level code that relies on this. The variants are not the same length, and they are intended not to be.

A: No, this is intentional so that the discriminants are not overwritten, and they can be properly initialized in the first place. Consider: 

     record
     case Boolean of
       False: (s1: String (42));
       True:  (s2: String (99));
     end;

If the strings would overlay, in particular their discriminants would occupy the same place in memory. How should it be initialized? Either way, it would be wrong for at least one of the variants ...

So, after a discussion in the ISO Pascal newsgroup where this topic came up concerning file variables (which also require some automatic initialization and finalization), we decided to do this in GPC for all types with automatic initialization and finalization (currently files, objects and schemata, including strings, in the future this might also be Delphi compatible classes and user-defined initialized and finalized types), since the standard does not guarantee variants to overlay, anyway ...

There are two ways in GPC to get guaranteed overlaying (both non-standard, of course, since the standard does not assume anything about internal representations; both BP compatible), absolute declarations and variable type casts. E.g., in order to overlay a byte array b to a variable v: 

     var
       b: array [1 .. SizeOf (v)] of Byte absolute v;

Or you can use type-casting: 

     type
       t = array [1 .. SizeOf (v)] of Byte;

then t (v) can be used as a byte array overlayed to v.

Node: Length byte, Next: , Previous: Strings in variant records, Up: Strings in GPC

3.4.3 Why does s[0] not contain the length?

Q: In standard Pascal you expect s[1] to align with the first character position of s and thus one character to the left is the length of s. Thus s[0] is the length of s. True?

A: This holds for UCSD/BP strings (which GPC does not yet implement, but that's planned). The only strings Standard Pascal knows are arrays of char without any length field.

GPC also supports Extended Pascal string schemata (see String schema), but they also don't have a length byte at "position 0", but rather a Length field (which is larger than one byte).

Node: Strings as value parameters, Next: , Previous: Length byte, Up: Strings in GPC

3.4.4 Watch out when using strings as parameters

Q: Any "gotchas" with string parameters?

A: Be careful when passing string literals as parameters to routines accepting the string as a value parameter and that internally modify the value of the parameter. Inside the routine, the value parameter gets a fixed capacity - the length of the string literal that was passed to it. Any attempt to assign a longer value will not work.

This only applies if the value parameter is declared as String. If it is declared as a string with a given capacity (e.g., String (255)), it gets this capacity within the routine.

Node: Short strings, Next: , Previous: Strings as value parameters, Up: Strings in GPC

3.4.5 Support for BP compatible short strings

Q: Two different kinds of strings with the same name - String - does make a bit of confusion. Perhaps the oldstyle strings could be renamed short string ?

A: When we implement the short strings, we'll have to do such a distinction. Our current planning goes like this:

String (n): string schema (EP compatible)

String [n]: short string (UCSD/BP compatible, where n must be <= 255)

String: dependent on flags, by default undiscriminated schema, but in BP mode (or with a special switch) short string of capacity 255 (UCSD/BP compatible).

Q: So when will these short strings be available?

A: It's been planned for over a year. The delay has been caused by more pressing problems.

Node: C strings, Previous: Short strings, Up: Strings in GPC

3.4.6 What about C strings?

A C string (char *) is an array of char, terminated with a #0 char.

C library functions require C, not Pascal style string arguments. However, Pascal style strings are automatically converted to C style strings when passed to a routine that expects C style strings. This works only if the routine reads from the string, not if it modifies it.

E.g., this is how you could access the system() call in your C library (which is not necessary anymore, since Execute is already built-in): 

     program SysCall;
     
     function System (CmdLine: CString): Integer; external name 'system';
     
     var
       Result: Integer;
     
     begin
       Result := System ('ls -l');
       WriteLn ('system() call returned: ', Result)
     end.

You could use the type PChar instead of CString. Both CString and PChar are predefined as ^Char - though we recommend CString because it makes it clearer that we're talking about some kind of string rather than a single character.

A lot of library routines in Pascal for many applications exist in the GPC unit and some other units. Where available, they should be preferred (e.g. Execute rather than system(), and then you won't have to worry about CStrings.)

Do not pass a C style string as a const or var argument if the C prototype says const char * or you will probably get a segfault.

Node: Getting Help, Next: , Previous: Strings in GPC, Up: FAQ

3.5 Getting Help

Please read the GPC Manual (info files or other formats) as well as the README and BUGS files that come with GPC (usually installed in directory /usr/local/doc/gpc), plus other docs that might help (the DJGPP FAQ if you use DJGPP, etc.) before you send email to the maintainers or mailing list.

In particular, the BUGS file contains information on how to submit bug reports in the most efficient way.

The Support chapter of the GPC Manual tells you where to find more information about GPC and how to contact the GPC developers. (see Support)

Node: Miscellaneous FAQ, Previous: Getting Help, Up: FAQ

3.6 Miscellaneous

Node: Contributing, Next: , Up: Miscellaneous FAQ

3.6.1 I want to contribute; where do I start?

If you want to contribute, please write to the mailing list, Mailing List.

Node: GPC web site, Next: , Previous: Contributing, Up: Miscellaneous FAQ

3.6.2 Where is the GNU Pascal web site?

The GPC homepage on the web, for information and downloads, is
http://www.gnu-pascal.de.

The GPC To-Do list, listing the latest features and fixed bugs can also be found there.

Node: About the FAQ, Previous: GPC web site, Up: Miscellaneous FAQ

3.6.3 About this FAQ

Current Maintainer: Russ Whitaker, russ@ashlandhome.net

This is the second incarnation of the GNU Pascal FAQ list, based on the previous FAQ by J.J. van der Heijden. Comments about, suggestions for, or corrections to this FAQ list are welcome.

Please make sure to include in your mail the version number of the document to which your comments apply (you can find the version at the beginning of this FAQ list).

Many people have contributed to this FAQ, only some of them are acknowledged above. Much of the info in, and inspiration for this FAQ list was taken from the GPC mailing list traffic, so you may have (unbeknownst to you) contributed to this list.

Node: Installation, Next: , Previous: FAQ, Up: Top

4 How to download, compile and install GNU Pascal.

Node: Download, Next: , Up: Installation

4.1 Where and what to download

You can download the source code of the current GNU Pascal release from 

     http://www.gnu-pascal.de/current/
and binaries for some platforms from 
     http://www.gnu-pascal.de/binary/

The binary archive files are named gpc-version.platform.extension - for example gpc-2.1.alpha-unknown-linux-gnu.tar.gz for GPC version 2.1 on an Alpha workstation running the Linux kernel with GNU C Library, or gpc-20000616.i386-pc-msdosdjgpp for GPC version 20000616 on an Intel IA32 compatible PC running DOS with DJGPP.

After you have downloaded the correct archive file for your platform, please read the installation notes on how to install such a binary distribution.

If you are running Dos or MS Windows, you will need additional tools - see "What else to download and where" below.

Current snapshots

GNU Pascal is subject to steady development. Alpha and beta snapshots (source only, use at your own risk) can be found at: 

     http://www.gnu-pascal.de/alpha/
     http://www.gnu-pascal.de/beta/

What else to download and where

When you are using GNU Pascal on a DOS system, you will need either the DJGPP or the EMX development environment (see below). On an OS/2 system, you will need EMX. On an MS Windows 95/98/NT system you will need either the CygWin or the mingw32 ot the MSYS environment.

GNU Pascal uses the compiler back-end from the GNU Compiler Collection, GNU CC or GCC. If you want to compile GPC, you will need the source of GCC as well as the source of GPC itself. From the same place as GPC, please download GCC 2.8.1, 2.95.x or 3.2.x. (It is also available from any GNU mirror; see http://www.gnu.org/software/gcc/.)

Libraries

For some of GPC's units, you will need some standard libraries. In particular:

Unit Platform Library
CRT Unix/terminal ncurses >= 5.0 (1), (2)
CRT Unix/X11 PDCurses (2)
CRT Dos, MS-Windows PDCurses (3)
GMP any gmp
RegEx any rx
(debugging) Unix, MS-Windows ElectricFence (4)

Notes:

(1) ncurses version 5.0 or newer is strongly recommended because older versions contain a bug that severely affects CRT programs.

(2) You can install both ncurses and PDCurses on a Unix system, and choose at compile time whether to generate a terminal or X11 version of your program.

(3) ncurses also runs under MS-Windows with CygWin (not mingw32, however), but doesn't appear to behave much differently from PDCurses on that platform.

(4) ElectricFence is not used by any unit, but can be used for debugging memory allocation bugs by simply linking it (see the accompanying documentation).

You can find those libraries on many places on the Net. Also, many GNU/Linux distributions, DJGPP mirrors and other OS distributions already contain some of the libraries. In any case, you can find the sources of the libraries (sometimes together with patches that you should apply before building if you choose to build from the sources) and binaries for some platforms in 

     http://www.gnu-pascal.de/libs/

For more information and descriptions of these libraries, see Libraries.

DJGPP

DJGPP is available from any SimTel mirror in the gnu/djgpp subdirectory; for addresses look into the DJGPP FAQ. To use GNU Pascal you need at least

We also recommend you to get:

EMX

EMX is an environment for creating 32-bit applications for DOS and OS/2. It is available from: 

     http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/index.html

To develop EMX programs with GNU Pascal you need at least

If your DOS box has DPMI (it does if you are using MS Windows or OS/2) you will also need RSX, available from the same sites as EMX in the subdirectory rsxnt.

The GNU development tools contain the GNU C compiler which is in fact not needed to use GNU Pascal. However, the C library is needed.

CygWin

CygWin is an environment which implements a POSIX layer under MS Windows, giving it large parts of the functionality of Unix. CygWin contains development tools such as an assembler, a linker, etc. GPC needs for operation. More information about CygWin can be found at 

     http://cygwin.com

mingw32

The Minimalists' GNU Win32 environment, mingw32, allows a large number of Unix programs - including GPC and GCC - to run under MS Windows 95/98/NT using native MS libraries. mingw32 ressources can be found at 

     http://www.mingw.org

Node: Binary Distributions, Next: , Previous: Download, Up: Installation

4.2 Installation instructions for a GPC binary distribution

To install a binary distribution, cd to the root directory and unpack the archive while preserving the stored directory structure. Under a Unix compatible system with GNU tar installed, the following (performed as root) will do the job: 

     # cd /
     # tar xzf archive.tar.gz

If you are using a tar utility other than GNU tar, it might be necessary to do the above in an explicit pipe: 

     # cd /
     # gzip -c -d archive.tar.gz | tar xf -

If you want to install a GPC binary distribution in another directory than it was prepared for (for example, if you do not have root access to the computer and want to install GPC somewhere under your home directory), you can do the following:

To install a ZIP archive under DOS with PKunzip, cd to the appropriate directory (usually \ for EMX, \DJGPP for DJGPP), then call PKunzip with the -d option: 

     C:\> cd djgpp
     C:\DJGPP> pkunzip -d archive.zip

where archive.zip is the name of the distribution file.

For DJGPP you must edit your djgpp.env in the DJGPP directory to complete the installation: Please copy the entries from [gcc] to create a new [gpc] section. The result may look as follows: 

     [gcc]
     COMPILER_PATH=%/>;COMPILER_PATH%%DJDIR%/bin
     LIBRARY_PATH=%/>;LIBRARY_PATH%%DJDIR%/lib
     
     [gpc]
     COMPILER_PATH=%/>;COMPILER_PATH%%DJDIR%/bin
     LIBRARY_PATH=%/>;LIBRARY_PATH%%DJDIR%/lib

If you are using the DJGPP version of GPC but do not have a DJGPP directory, please download and install DJGPP (see Download).

Binary distributions include libgcc.a and specs, files that are normally part of GCC. If you have GCC installed, they will be replaced unless you manually install the archive.

Node: Compiling GPC, Next: , Previous: Binary Distributions, Up: Installation

4.3 Compiling GPC

The preferred way to distribute GNU software is distribution of the source code. However, it can be a non-trivial exercise to build GNU Pascal on some non-Unix systems, so we also provide ready-to-run binaries for a number of platforms. (See Binary Distributions for how to install a binary distribution.)

GPC is based on the GNU Compiler Collection, GNU CC or GCC. You will need the GCC sources to build it. It must be the same version as the one GPC is implemented with - 2.8.1, 2.95.x or 3.2.x as of this writing. Although you need GCC to build the GNU Pascal compiler, you don't need GCC to compile Pascal programs once GNU Pascal is installed. (However, using certain libraries will require compiling C wrappers, so it is a good idea to install the C compiler as well.)

Because GNU Pascal shares its back-end with GCC, it should run on any system supported by GCC. A full list of platforms supported by GCC can be found in the GCC installation instructions.

The GCC source can be obtained from any mirror of the GNU FTP site, ftp://ftp.gnu.org/gnu/gcc/. The "core" distribution is sufficient for GPC.

Here is the generic procedure for installing GNU Pascal on a Unix system. See Compilation Notes for extra information needed to install GPC on DOS-like platforms.

  1. Checking the prerequisites

    Make sure that GNU make is installed and that you use it in the following steps. When unsure, you can try make --version and/or gmake --version. It should tell you that it is GNU make. If you don't have it, you can obtain it from http://www.gnu.org/software/make/.

    (In the following, we will simply speak of make when invoking GNU make; you might need to call gmake instead.)

    You also need a patch program. If such a program is not installed on your system, you can get GNU patch from http://www.gnu.org/directory/patch.html.

    For extracting the example programs from the documentation to the doc/docdemos directory a non-crippled sed is needed. GNU sed is known to work.

    If you have downloaded a "minimal" source distribution, most derived files have to be rebuilt. This happens automatically, but you need additional tools: bash, bzip2, GNU sed, GNU awk, GNU m4, bison (at least version 1.875), flex, autoconf (version 2.12), help2man, texinfo (at least version 4.2). Make sure that these are installed. The minimal distributions are compressed with bzip2 instead of gzip, so substitute it in the instructions below.

    If you want to build the GPC WWW pages you will also need a TeX distribution (including pdftex and dvips).

    If you run into trouble during the installation process, please check whether you are using outdated versions of the required utilities and upgrade if necessary.

    The GNU versions of the packages above are available from http://www.gnu.org/software/, in a subdirectory whose name is the name of the package.

  2. Unpacking the source

    From a directory of your choice (e.g. /home/fred), unpack the GCC and GNU Pascal source distributions. This will create separate subdirectories for GCC and GPC. Let us assume gcc-2.95.3 and gpc-20030209 in this example. 

              % cd /home/fred
          % gzip -c -d gcc-core-2.95.3.tar.gz | tar xf -
          % gzip -c -d gpc-20030209.tar.gz | tar xf -

    cd to the GPC directory and move the contents (a subdirectory p) to the subdirectory gcc of the GCC directory: 

              % mv /home/fred/gpc-20030209/p /home/fred/gcc-2.95.3/gcc/

    Instead of moving the directory, it is now also possible to make a symbolic link (if the OS supports symlinks). This is useful if you want to build GPC with several different GCC versions: 

              % ln -s /home/fred/gpc-20030209/p /home/fred/gcc-2.95.3/gcc/p

    It is recommended, though not required, to use a separate directory for building the compiler, rather than compiling in the source directory. In this example, let us create /home/fred/gpc-build for this purpose: 

              % mkdir /home/fred/gpc-build

    If you use a separate directory, you do not need to write into the GCC source directory once you have patched the GCC source (see below), and can build GPC for more than one platform from the same source tree.

    In case you are re-using a directory where you have already built GCC and/or GPC for a different target machine, do make distclean to delete all files that might be invalid. One of the files this deletes is Makefile; if make distclean complains that Makefile does not exist, it probably means that the directory is already suitably clean.

  3. Configuring and building GCC

    GNU Pascal is automatically configured with GCC. Configuration of GCC is treated in depth in the GCC installation instructions. The normal procedure is as follows:

    cd to the GPC build directory. From there, run the configure script in the GCC source directory: 

              % cd /home/fred/gpc-build
          % /home/fred/gcc-2.95.3/configure --enable-languages=pascal

    This creates all the necessary config files, links and Makefile in the GCC object directory.

    Note 1: The configuration will prompt you for patching the GCC source for GPC support, so you need write access to that directory. All changes to GCC are surrounded by #ifdef GPC ... #endif, so they should not interfere when you build a C compiler from this source tree.

    Note 2: The --enable-languages=pascal option means that we only want to build the Pascal compiler and not, for instance, the C++ compiler.

    Note 3: The standard base directory for installing GCC and GPC is /usr/local. If you want to install files to an alternate directory dir, specify --prefix=dir when you run configure. For installing into a system directory such as /usr/local you will, of course, need appropriate permissions (often root). Therefore, if you want to install GPC on a system where you don't have those permissions, you must specify a prefix (e.g., $HOME/usr).

  4. Putting other GNU tools in place

    Some environments require other GNU tools (such as the GNU assembler or linker) instead of the standard system tools for GCC to work. (See the GCC installation instructions for details.) If this is the case for your system, install the required tools in the GPC build directory under the names as, ld, or whatever is appropriate. This will enable the compiler to find the proper tools for compilation of the program enquire (a part of GCC) and to install the GNU tools to a place where they are found by GCC but do not interfere with the standard system tools.

    Alternatively, you can do subsequent compilation using a value of the PATH environment variable such that the necessary GNU tools come before the standard system tools.

  5. Compiling GPC

    Once you are satisfied with the configuration as determined by configure, you can build the compiler: 

              % make

    Notice that this procedure will build the C compiler (and maybe some other compilers) too, because that is used to compile the GPC runtime library.

    Optionally, you may supply CFLAGS, LDFLAGS or RTSFLAGS. CFLAGS is used for compiler and RTS, RTSFLAGS are for RTS only, i.e.: make CFLAGS="-O2" RTSFLAGS=-Wall

    Note: The documentation may fail to build from *.texi sources if GCC 2.95.x tries to use an older version of makeinfo supplied in GCC package itself. This can be prevented by supplying explicit instruction to use your system's makeinfo: 

              % make MAKEINFO=`which makeinfo`

    optionally followed by the rest of arguments.

  6. Completing the installation

    When everything has been compiled, you can check the installation process with: 

              % make -n install

    To complete the installation, run the command make install. You need write access to the target directories (/usr/local/bin, /usr/local/lib, /usr/local/info, /usr/local/doc, and /usr/local/man in this example), so this is usually done as root: 

              % su -c "make install"

    If you want to install only the Pascal compiler (for example if you already have the correct version of GCC installed), cd to the gcc subdirectory of the build directory (e.g. /home/fred/gpc-build/gcc) and run make pascal.install. This installation process does not overwrite existing copies of libgcc.a or specs, should they exist.

    However, if you do not have the exactly matching GCC version installed, you might need some additional files (otherwise GPC will complain about missing files at runtime). You can install them by doing make pascal.install-with-gcc in the gcc subdirectory of the build directory.

    There is a (partial) translation of the GPC manual into Croatian available now. It is not installed by default. If you want to install it, do a pascal.install-hr in the gcc directory. This will install the manpage gpc-hr.1 and the info documentation gpc-hr.info*. Other formats like PS, PDF and HTML can be built manually (it's also easy to add appropriate make targets for them when needed).

    Also from the gcc subdirectory you can do some more "exotic" builds. For instance, you can build the GPC WWW pages by typing make pascal.html or a binary distribution by typing make pascal.bindist. See the Makefile in that directory for more examples.

Node: Compilation Notes, Next: , Previous: Compiling GPC, Up: Installation

4.4 Compilation notes for specific platforms

Node: MS-DOS with DJGPP, Next: , Up: Compilation Notes

4.4.1 MS-DOS with DJGPP

The only compiler that is capable of compiling the GNU Compiler Collection (GNU CC or GCC) under MS-DOS is GCC itself. In order to compile GPC or GCC for MS-DOS with DJGPP you will therefore need either a working copy of DJGPP installed, or you will have to cross-build from a non-MS-DOS system.

Building GPC under MS-DOS with DJGPP follows the same scheme as building GPC under a Unix-like system: Place the p subdirectory in the gcc directory and follow the instructions for compiling GCC. This requires bash and many other tools installed, and you must be very careful at many places to circumvent the limitations of the DOS platform.

Our preferred way to build GPC for DJGPP is to cross-build it from a Unix-like platform - which is much easier. For instructions, see Cross-Compilers and Crossbuilding.

Node: MS-DOS or OS/2 with EMX, Next: , Previous: MS-DOS with DJGPP, Up: Compilation Notes

4.4.2 MS-DOS or OS/2 with EMX

EMX is a free 32-bit DOS extender which adds some properties of Unix to MS-compatible DOS and IBM's OS/2 operating systems.

As of this writing, we are not aware of current versions of GCC for EMX, and EMX support in GPC has not been maintained. Please contact us if you know about recent development in EMX and are interested in continuing EMX support in GPC.

Node: MS Windows 95/98/NT, Previous: MS-DOS or OS/2 with EMX, Up: Compilation Notes

4.4.3 MS Windows 95/98/NT

There are two ports of the GNU development tools to MS Windows 95/98/NT: CygWin and mingw32.

The CygWin environment implements a POSIX layer under MS Windows, giving it large parts of the functionality of Unix. Thus, compiling GCC and GPC under the CygWin environment can be done following the instructions for compiling it under a Unix-like system (see Compiling GPC).

The Minimalists' GNU Win32 environment, mingw32, uses the native crtdll.dll library of MS Windows. It is much smaller than CygWin, but it is not self-hosting and must be crossbuilt from another system (see Crossbuilding).

Node: Cross-Compilers, Next: , Previous: Compilation Notes, Up: Installation

4.5 Building and Installing a cross-compiler

GNU Pascal can function as a cross-compiler for many machines. Information about GNU tools in a cross-configuration can be found at ftp://ftp.cygnus.com/pub/embedded/crossgcc/.

Since GNU Pascal generates assembler code, you need a cross-assembler that GNU Pascal can run, in order to produce object files. If you want to link on other than the target machine, you need a cross-linker as well. It is straightforward to install the GNU binutils to act as cross-tools - see the installation instructions of the GNU binutils for details.

You also need header files and libraries suitable for the target machine that you can install on the host machine. Please install them under prefix/platform/include/, for instance /usr/local/i386-pc-msdosdjgpp/include/ for a cross-compiler from a typical Unix-like environment to MS-DOS with DJGPP.

Configuration and compilation of the compiler can then be done using the scripts cfgpc and mkgpc which are included in the source distribution in the subdirectory p/script. Please call them with the -h option for instructions.

Node: Crossbuilding, Previous: Cross-Compilers, Up: Installation

4.6 Crossbuilding a compiler

Using a cross-compiler to build GNU Pascal results in a compiler binary that runs on the cross-target platform. This is called "crossbuilding". A possible reason why anybody would want to do this, is when the platform on which you want to run the GNU Pascal compiler is not self-hosting. An example is mingw32.

To crossbuild GNU Pascal, you have to install a cross-compiler for your target first, see Cross-Compilers.

As when building a cross-compiler, configuration and compilation of the compiler can be done using the scripts cfgpc and mkgpc which are included in the source distribution in the subdirectory p/script. Please call them with the -h option for instructions.

Node: Invoking GPC, Next: , Previous: Installation, Up: Top

5 Command Line Options supported by GNU Pascal.

GPC is a command-line compiler, i.e., to compile a program you have to invoke gpc passing it the name of the file you want to compile, plus options.

GPC supports all command-line options that GCC knows, except for many preprocessor options. For a complete reference and descriptions of all options, see GCC Command Options. Below, you will find a list of the additional options that GPC supports, and a list of GPC's most important options (including some of those supported by GCC as well).

You can mix options and file names on the command line. For the most part, the order doesn't matter. Order does matter, e.g., when you use several options of the same kind; for example, if you specify -L more than once, the directories are searched in the order specified. Note: Since many options have multiletter names; multiple single-letter options may not be grouped as is possible with many other programs: -dr is very different from -d -r.

Many options have long names starting with -- or, completely equivalent -f. E.g., --mixed-comments is the same as -fmixed-comments. Some options tell GPC when to give warnings, i.e. diagnostic messages that report constructs which are not inherently erroneous but which are risky or suggest there may have been an error. Those options start with -W.

Most GPC specific options can also be changed during one compilation by using compiler directives in the source, e.g. {$X+} or {$extended-syntax} for --extended-syntax (see Compiler Directives).

GPC understands the same environment variables GCC does (see Environment Variables Affecting GCC). In addition, GPC recognizes GPC_EXEC_PREFIX with the same meaning that GCC_EXEC_PREFIX has to GCC. GPC also recognizes GCC_EXEC_PREFIX, but GPC_EXEC_PREFIX takes precedence.

Some of the long options (e.g., --unit-path) take an argument. This argument is separated with a = sign, e.g.: 

     --unit-path=/home/foo/units

Node: GPC Command Line Options, Next: , Up: Invoking GPC

5.1 GPC options besides those of GCC.

The following table lists the command line options GPC understands in addition to those understood by GCC.

--debug-tree
(For GPC developers.) Show the internal representation of a given tree node (name or address).
--debug-gpi
(For GPC developers.) Show what is written to and read from GPI files (huge output!).
--debug-automake
(For GPC developers.) Give additional information about the actions of automake.
--debug-source
Output the source while it is being processed.
--no-debug-source
Do not output the source while it is being processed (default).
--no-debug-info
Inhibit -g options (temporary work-around, this option may disappear in the future).
--progress-messages
Output source file names and line numbers while compiling.
--no-progress-messages
Do not output source file names and line numbers while compiling (default).
--progress-bar
Output number of processed lines while compiling.
--no-progress-bar
Do not output number of processed lines while compiling (default).
--automake-gpc
Set the Pascal compiler invoked by automake.
--automake-gcc
Set the C compiler invoked by automake.
--automake-g++
Set the C++ compiler invoked by automake.
--amtmpfile
(Internal switch used for automake).
--autolink
Automatically link object files provided by units/modules or {$L ...} (default).
--no-autolink
Do not automatically link object files provided by units/modules/{$L ...}.
--automake
Automatically compile changed units/modules/{$L ...} files and link the object files provided.
--no-automake
Same as --no-autolink.
--autobuild
Automatically compile all units/modules/{$L ...} files and link the object files provided.
--no-autobuild
Same as --no-autolink.
--maximum-field-alignment
Set the maximum field alignment in bits if pack-struct is in effect.
--ignore-packed
Ignore packed in the source code (default in --borland-pascal).
--no-ignore-packed
Do not ignore packed in the source code (default).
--ignore-garbage-after-dot
Ignore anything after the terminating . (default in --borland-pascal).
--no-ignore-garbage-after-dot
Complain about anything after the terminating . (default).
--extended-syntax
same as --ignore-function-results --pointer-arithmetic --cstrings-as-strings -Wno-absolute (same as {$X+}).
--no-extended-syntax
Opposite of --extended-syntax (same as {$X-}).
--ignore-function-results
Do not complain when a function is called like a procedure.
--no-ignore-function-results
Complain when a function is called like a procedure (default).
--pointer-arithmetic
Enable pointer arithmetic.
--no-pointer-arithmetic
Disable pointer arithmetic (default).
--cstrings-as-strings
Treat CStrings as strings.
--no-cstrings-as-strings
Do not treat CStrings as strings (default).
-Wabsolute
Warn about variables at absolute adresses and absolute variable with non-constant addresses (default).
-Wno-absolute
Do not warn about variables at absolute adresses and absolute variable with non-constant addresses (default).
--short-circuit
Guarantee short-circuit Boolean evaluation (default; same as {$B-}).
--no-short-circuit
Do not guarantee short-circuit Boolean evaluation (same as {$B+}).
--mixed-comments
Allow comments like { ... *) as required in ISO Pascal (default in ISO 7185/10206 Pascal mode).
--no-mixed-comments
Ignore { and } within (* ... *) comments and vice versa (default).
--nested-comments
Allow nested comments like { { } } and (* (* *) *).
--no-nested-comments
Do not allow nested comments (default).
--delphi-comments
Allow Delphi style // comments (default).
--no-delphi-comments
Do not allow Delphi style // comments.
--macros
Expand macros (default).
--no-macros
Do not expand macros (default with --ucsd-pascal, --borland-pascal or --delphi).
--truncate-strings
Truncate strings being assigned to other strings of too short capacity..
--no-truncate-strings
Treat string assignments to other strings of too short capacity as errors..
--exact-compare-strings
Do not blank-pad strings for comparisons.
--no-exact-compare-strings
Blank-pad strings for comparisons.
--double-quoted-strings
Allow strings enclosed in "\" (default).
--no-double-quoted-strings
Do not allow strings enclosed in "\" (default with dialect other than --mac-pascal).
--longjmp-all-nonlocal-labels
Use longjmp for all nonlocal labels.
--no-longjmp-all-nonlocal-labels
Use longjmp only for nonlocal labels in the main program (default).
--io-checking
Check I/O operations automatically (same as {$I+}) (default).
--no-io-checking
Do not check I/O operations automatically (same as {$I-}).
--range-checking
Do automatic range checks (same as {$R+}) (default).
--no-range-checking
Do not do automatic range checks (same as {$R-}).
--stack-checking
Enable stack checking (same as {$S+}).
--no-stack-checking
Disable stack checking (same as {$S-} (default)).
--read-base-specifier
In read statements, allow input base specifier n# (default).
--no-read-base-specifier
In read statements, do not allow input base specifier n# (default in ISO 7185 Pascal).
--read-hex
In read statements, allow hexadecimal input with $ (default).
--no-read-hex
In read statements, do not allow hexadecimal input with $ (default in ISO 7185 Pascal).
--read-white-space
In read statements, require whitespace after numbers.
--no-read-white-space
In read statements, do not require whitespace after numbers (default).
--write-clip-strings
In write statements, truncate strings exceeding their field width (Write (SomeLongString : 3)).
--no-write-clip-strings
Do not truncate strings exceeding their field width.
--write-real-blank
Output a blank in front of positive reals in exponential form (default).
--no-write-real-blank
Do not output a blank in front of positive reals in exponential form.
--write-capital-exponent
Write real exponents with a capital E.
--no-write-capital-exponent
Write real exponents with a lowercase e.
--transparent-file-names
Derive external file names from variable names.
--no-transparent-file-names
Do not derive external file names from variable names (default).
--field-widths
Optional colon-separated list of default field widths for Integer, Real, Boolean, LongInt, LongReal.
--no-field-widths
Reset the default field widths.
--pedantic
Reject everything not allowed in some dialect, e.g. redefinition of its keywords.
--no-pedantic
Don't give pedantic warnings.
--typed-address
Make the result of the address operator typed (same as {$T+}, default).
--no-typed-address
Make the result of the address operator an untyped pointer (same as {$T-}).
--enable-keyword
Enable a keyword, independently of dialect defaults.
--disable-keyword
Disable a keyword, independently of dialect defaults.
--assertions
Enable assertion checking (default).
--no-assertions
Disable assertion checking.
--setlimit
Define the range for set of Integer etc..
--gpc-main
External name for the program's entry point (default: main).
--interface-only
Compile only the interface part of a unit/module and exit (creates .gpi file, no .o file.
--implementation-only
Do not produce a GPI file; only compile the implementation part.
--executable-file-name
Name for the output file, if specified; otherwise derive from main source file name.
--unit-path
Directories where to look for unit/module sources.
--no-unit-path
Forget about directories where to look for unit/module sources.
--object-path
Directories where to look for additional object (and source) files.
--no-object-path
Forget about directories where to look for additional object (and source) files.
--executable-path
Path where to create the executable file.
--no-executable-path
Create the executable file in the directory where the main source is (default).
--unit-destination-path
Path where to create object and GPI files of Pascal units.
--no-unit-destination-path
Create object and GPI files of Pascal units in the current directory (default).
--object-destination-path
Path where to create additional object files (e.g. of C files, not Pascal units).
--no-object-destination-path
Create additional object files (e.g. of C files, not Pascal units) in the current directory (default).
--no-default-paths
Do not add a default path to the unit and object path.
--gpi-destination-path
(Internal switch used for automake).
--uses
Add an implicit uses clause.
--init-modules
Initialize the named modules in addition to those imported regularly; kind of a kludge.
--cidefine
Define a case-insensitive macro.
--csdefine
Define a case-sensitive macro.
--big-endian
Tell GPC that the system is big-endian (for those targets where it can vary).
--little-endian
Tell GPC that the system is little-endian (for those targets where it can vary).
--print-needed-options
Print the needed options.
-Wwarnings
Enable warnings (same as {$W+}).
-Wno-warnings
Disable all warnings (same as {$W-}).
-Widentifier-case-local
Warn about an identifier written with varying case within one program/module/unit.
-Wno-identifier-case-local
Same as -Wno-identifier-case.
-Widentifier-case
Warn about an identifier written with varying case.
-Wno-identifier-case
Do not warn about an identifier written with varying case (default).
-Winterface-file-name
Warn when a unit/module interface differs from the file name.
-Wno-interface-file-name
Do not warn when a unit/module interface differs from the file name (default).
--methods-always-virtual
Make all methods virtual (default in --mac-pascal).
--no-methods-always-virtual
Do not make all methods virtual (default).
-Wimplicit-abstract
Warn when an object type not declared abstract contains an abstract method (default).
-Wno-implicit-abstract
Do not warn when an object type not declared abstract contains an abstract method.
-Winherited-abstract
Warn when an abstract object type inherits from a non-abstract one (default).
-Wno-inherited-abstract
Do not warn when an abstract object type inherits from a non-abstract one.
-Wobject-assignment
Warn when when assigning objects or declaring them as value parameters or function results (default).
-Wno-object-assignment
Do not warn when assigning objects or declaring them as value parameters or function results (default in --borland-pascal).
-Wimplicit-io
Warn when Input or Output are used implicitly.
-Wno-implicit-io
Do not warn when Input or Output are used implicitly (default).
-Wfloat-equal
Warn about = and <> comparisons of real numbers.
-Wno-float-equal
Do not warn about = and <> comparisons of real numbers.
-Wtyped-const
Warn about misuse of typed constants as initialized variables (default).
-Wno-typed-const
Do not warn about misuse of typed constants as initialized variables.
-Wnear-far
Warn about use of useless near or far directives (default).
-Wno-near-far
Do not warn about use of useless near or far directives.
-Wunderscore
Warn about double/leading/trailing underscores in identifiers.
-Wno-underscore
Do not warn about double/leading/trailing underscores in identifiers.
-Wsemicolon
Warn about a semicolon after then, else or do (default).
-Wno-semicolon
Do not warn about a semicolon after then, else or do.
-Wlocal-external
Warn about local external declarations.
-Wno-local-external
Do not warn about local external declarations.
-Wdynamic-arrays
Warn about arrays whose size is determined at run time (including array slices).
-Wno-dynamic-arrays
Do not warn about arrays whose size is determined at run time (including array slices).
-Wmixed-comments
Warn about mixed comments like { ... *).
-Wno-mixed-comments
Do not warn about mixed comments.
-Wnested-comments
Warn about nested comments like { { } }.
-Wno-nested-comments
Do not warn about nested comments.
--classic-pascal-level-0
Reject conformant arrays and anything besides ISO 7185 Pascal.
--standard-pascal-level-0
Synonym for --classic-pascal-level-0.
--classic-pascal
Reject anything besides ISO 7185 Pascal.
--standard-pascal
Synonym for --classic-pascal.
--extended-pascal
Reject anything besides ISO 10206 Extended Pascal.
--object-pascal
Reject anything besides (the implemented parts of) ANSI draft Object Pascal.
--ucsd-pascal
Try to emulate UCSD Pascal.
--borland-pascal
Try to emulate Borland Pascal, version 7.0.
--delphi
Try to emulate Borland Pascal, version 7.0, with some Delphi extensions.
--pascal-sc
Be strict about the implemented Pascal-SC extensions.
--vax-pascal
Support (a few features of) VAX Pascal.
--sun-pascal
Support (a few features of) Sun Pascal.
--mac-pascal
Support (some features of) traditional Macintosh Pascal compilers.
--gnu-pascal
Undo the effect of previous dialect options, allow all features again.

Node: GPC Options, Previous: GPC Command Line Options, Up: Invoking GPC

5.2 The most commonly used options to GPC

As the most simple example, calling 

     gpc foo.pas

tells GPC to compile the source file foo.pas and to produce an executable of the default name which is foo.exe on EMX, a.exe on Cygwin, both a.out and a.exe on DJGPP, and a.out on most other platforms.

Users familiar with BP, please note that you have to give the file name extension .pas: GPC is a common interface for a Pascal compiler, a C, ObjC and C++ compiler, an assembler, a linker, and perhaps an Ada and a FORTRAN compiler. From the extension of your source file GPC figures out which compiler to run. GPC recognizes Pascal sources by the extension .pas, .p, .pp or .dpr. GPC also accepts source files in other languages (e.g., .c for C) and calls the appropriate compilers for them. Files with the extension .o or without any special recognized extension are considered to be object files or libraries to be linked.

Another example: 

     gpc -O2 -Wall --executable-file-name --automake --unit-path=units foo.pas

This will compile the source file foo.pas to an executable named foo (--executable-file-name) with fairly good optimization (-O2), warning about possible problems (-Wall). If the program uses units or imports modules, they will be searched for in a directory called units (--unit-path) and automatically compiled and linked (--automake).

The following table lists the most commonly used options to GPC.

--automake
Check whether modules/units used must be recompiled and do the recompilation when necessary.
--unit-path=dir[:dir...]
Search the given directories for units and object files.
--object-path=dir[:dir...]
Search the given directories for object files.
--unit-destination-path=dir
Place compiled units (GPI and object files) into the directory dir. The default is the current directory.
--object-destination-path=dir
Place compiled object files (e.g., from C files, but not from Pascal units) into the directory dir. The default is the directory given with --unit-destination-path.
--executable-path=dir
Place the executable compiled into the directory dir. The default is the main source file's directory.
-o file
Place output in file file. This applies regardless to whatever sort of output is being produced, whether it be an executable file, an object file, an assembler file, etc.

Since only one output file can be specified, it does not make sense to use -o when compiling more than one input file, unless you are producing an executable file as output.

--executable-file-name[=name]
Derive the executable file name from the source file name, or use name as the executable file name. The difference to the -o option is that --executable-file-name considers the --executable-path, while -o does not and accepts a file name with directory. Furthermore, --executable-file-name only applies to executables, not to other output formats selected.
-Ldir
Search the directory dir for libraries. Can be given multiple times.
-Idir
Search the directory dir for include files. Can be given multiple times.
-llibrary
Search the library named library when linking. This option must be placed on the command line after all source or object files or other libraries that reference the library.
-O[n]
Select the optimization level. Without optimization (or -O0 which is the default), the compiler's goal is to reduce the compilation time and to make debugging produce the expected results. Statements are independent: if you stop the program with a breakpoint between statements, you can then assign a new value to any variable or change the program counter to any other statement in the same routine and get exactly the results you would expect from the source code.

With optimization, the compiler tries to reduce code size and execution time. The higher the value of n, the more optimizations will be done, but the longer the compilation will take.

If you use multiple -O options, with or without n, the last such option is the one that is effective.

-g
Produce debugging information suitable for gdb. Unlike some other compilers, GNU Pascal allows you to use -g with -O. The shortcuts taken by optimized code may occasionally produce surprising results: some variables you declared may not exist at all; flow of control may briefly move where you did not expect it; some statements may not be executed because they compute constant results or their values were already at hand; some statements may execute in different places because they were moved out of loops. Nevertheless it proves possible to debug optimized output. This makes it reasonable to use the optimizer for programs still in the testing phase.
-s
Remove all symbol table and relocation information from the executable. Note: this has no influence on the performance of the compiled executable.
-Wall
Give warnings for a number of constructs which are not inherently erroneous but which are risky or suggest there may have been an error. There are additional warning options not implied by -Wall, see the GCC warning options (see Options to Request or Suppress Warnings), while -Wall only warns about such constructs that should be easy to avoid in programs. Therefore, we suggest using -Wall on most sources.

Note that some warnings (e.g., those about using uninitialized variables) are never given unless you compile with optimization (see above), because otherwise the compiler doesn't analyze the usage patterns of variables.

-Werror
Turn all warnings into errors.
-S
Stop after the stage of compilation proper; do not assemble. The output is in the form of an assembler code file for each source file. By default, the assembler file name for a source file is made by replacing the extension with .s.
-c
Compile and assemble the source files, but do not link. The output is in the form of an object file for each source file. By default, the object file name for a source file is made by replacing the extension with .o.
-static
On systems that support dynamic linking, this prevents linking with the shared libraries, i.e. forces static linking. On other systems, this option has no effect.
-Dmacro[=def]
Define the macro and conditional symbol macro as def (or as 1 if def is omitted).
-b machine
The argument machine specifies the target machine for compilation. This is useful when you have installed GNU Pascal as a cross-compiler.
-v
Print (on standard error) the commands executed to run the stages of compilation. Also print the version number of the compiler driver program and of the preprocessor and the compiler proper.
--classic-pascal-level-0
--classic-pascal
--extended-pascal
--object-pascal
--ucsd-pascal
--borland-pascal
--pascal-sc
GNU Pascal supports the features of several different Pascal standards and dialects. By default, they are all enabled. These switches tell GPC to restrict itself to the features of the specified standard. It does not enable any additional features. Warnings about certain dangerous constructs which would be valid in the specified dialect (e.g., assignment to a typed constant with --borland-pascal) are suppressed.

By default, GNU Pascal allows the redefinition of some keywords. Each of these switches causes GNU Pascal to forbid the redefinition of keywords of the specified standard.

Valid ISO 7185 Pascal programs should compile properly with or without --classic-pascal. However, without this option, certain GNU extensions and Pascal features from other dialects are supported as well. With this option, they are rejected.

These options are not intended to be useful; they exist only to satisfy pedants who would otherwise claim that GNU Pascal fails to support the ISO Standard or is not really compatible to Borland Pascal, or whatever. We recommend, rather, that users take advantage of the extensions of GNU Pascal and disregard the limitations of other compilers.

-pedantic-errors
Produce errors rather than warnings for portability violations. Unlike in C, this does not imply the -pedantic option, so you can, for instance, use -pedantic-errors without -pedantic, but with --extended-pascal.
--gpc-main=name
Name the entry point of the main program name instead of main on the linker level. This is useful, e.g., when working with some C libraries which define their own main function and require the program's main entry point to be named differently. (This option should preferably be used as a compiler directive in the unit or module which links to that strange C library, rather than be given on the command-line.)

Node: Programming, Next: , Previous: Invoking GPC, Up: Top

6 The Programmer's Guide to GPC

This chapter is still under development.

This chapter tells you how the source of a valid GNU Pascal program should look like. You can use it as tutorial about the GNU Pascal language, but since the main goal is to document all special GPC features, implementation-dependent stuff, etc., expect a steep learning curve.

This chapter does not cover how to compile your programs and to produce an executable - this is discussed above in Invoking GPC.

Node: Source Structures, Next: , Up: Programming

6.1 Source Structures

A source file accepted by GNU Pascal may contain up to one program, zero or more ISO-style modules, and/or zero or more UCSD-style units. Units and modules can be mixed in one project.

One trivial example for a valid GPC source file follows. Note that the code below may either be in one source file, or else the unit and the program may be in separate source files. 

     unit DemoUnit;
     
     interface
     
     procedure Hello;
     
     implementation
     
     procedure Hello;
     begin
       WriteLn ('Hello, world!')
     end;
     
     end.
     
     program UnitDemo;
     
     uses
       DemoUnit;
     
     begin
       Hello
     end.

Node: The Program, Next: , Up: Source Structures

6.1.1 The Source Structure of Programs

A generic GNU Pascal program looks like the following: 

     program name (Input, Output);
     
     import_part
     
     declaration_part
     
     begin
       statement_part
     end.

The program headline may be omitted in GPC, but a warning will be given except in --borland-pascal mode.

While the program parameters (usually Input, Output) are obligatory in ISO Pascal if you want to use ReadLn and WriteLn, they are optional in GNU Pascal. GPC will warn about such missing parameters in --extended-pascal mode. However if you give parameters to the program headline, they work like ISO requires.

The import_part consists either of an ISO-style import specification or a UCSD/Borland-style uses clause. While import is intended to be used with interfaces exported by ISO 10206 Extended Pascal modules, and uses is intended to be used with units, this is not enforced. (See also uses, import.)

The declaration_part consists of label, constant, type, variable or subroutine declarations in free order. However, every identifier must be declared before it is used. The only exception are type identifiers pointing to another type identifier which may be declared below.

The statement_part consists of a sequence of statements.

As an extension, GPC supports a "declaring statement" which can be used in the statement part to declare variables (see var).

Node: Label Declaration, Next: , Previous: The Program, Up: Source Structures

6.1.2 Label Declaration

A label declaration has the following look: 

     label
       label_name, ..., label;

A label declaration part starts with the reserved word label, which contains a list of labels.

See also

label, goto

Node: Constant Declaration, Next: , Previous: Label Declaration, Up: Source Structures

6.1.3 Constant Declaration

A constant declaration has the following look: 

     const
       constant_identifier = constant_expression;
       ...
       constant_identifier = constant_expression;

A constant declaration part starts with the reserved word const. It declares a constant_identifier which is defined by constant_expression. This expression has to be evaluatable during compilation time, i.e. it can include numbers, parentheses, predefined operators, sets and type casts (the last, however, is a Borland extension). In ISO 7185 Pascal, constant_expression must be a constant or a set. All Pascal Dialects but ISO-Pascal allow the use of these intrinsic functions in constant_expression: Abs, Round, Trunc, Chr, Ord, Length, Pred, Succ, SizeOf, Odd.

In Borland Pascal, in the constant declaration part variables can be declared as well, which are given an initial value. These variables are called "typed constants". It is good style to avoid this use, especially since Extended Pascal and GNU Pascal allow to initialize a variable in variable declaration part or give a type a preset value on declaration. 

     const
       FiveFoo      = 5;
       StringFoo    = 'string constant';
       AlphabetSize = Ord ('Z') - Ord ('A') + 1;
     
     type
       PInteger     = ^Integer;     { Define a pointer to an Integer }
     
     const
       { Constant which holds a pointer to an Integer at address 1234 }
       AddressFoo   = PInteger (1234);

See also

Subroutine Parameter List Declaration

Node: Type Declaration, Next: , Previous: Constant Declaration, Up: Source Structures

6.1.4 Type Declaration

A type declaration looks like this: 

     type
       type_identifier = type_definition;
       ...
       type_identifier = type_definition;
or, with preset content: 
     type
       type_identifier = type_definition value constant_expression;
       ...
       type_identifier = type_definition value constant_expression;

A type declaration part begins with the reserved word type. It declares a type_identifier which is defined by type_definition. A type definition either can be an array, a record, a schema, a set, an object, a subrange, an enumerated type, a pointer to another type_identifier or simply another type_identifier which is to alias. If a schema type is to be declared, type_identifier is followed by a discriminant enclosed in parentheses: 

     type_identifier (discriminant) = schema_type_definition;

If value is specified, followed by a constant satisfying the type definition, every variable of this type is initialized with constant_expression, unless it is initialized by value itself. The reserved word value can be replaced by =, however value is not allowed in ISO-Pascal and Borland Pascal, and the replacement by = is not allowed in Extended Pascal.

Type declaration example

     type
       { This side is the }     { That side is the }
       { type declaration }     { type definition  }
     
       Arrayfoo            = array [0 .. 9] of Integer;  { array definition }
       Recordfoo           = record                      { record definition }
                               Bar: Integer;
                             end;
     
            { schema def with discriminants ``x, y: Integer'' }
       SchemaFoo (x, y: Integer) = array [x .. y] of Integer;
       CharSetFoo          = set of Char;              { Def of a set }
       ObjectFoo           = object                    { Def of an object }
                               procedure DoAction;
                               constructor Init;
                               destructor Done;
                             end;
       SubrangeFoo         = -123..456;                { subrange def }
     
       EnumeratedFoo       = (Pope,John,the,Second);   { enum type def }
            { Def of a pointer to another type identifier }
       PInteger            = ^arrayfoo;
            { Def of an alias name for another type identifier }
       IdentityFoo         = Integer;
            { Def of an integer which was initialized by 123 }
       InitializedFoo      = Integer value 123;

See also

Type Definition, Data Types, Variable Declaration

Node: Variable Declaration, Next: , Previous: Type Declaration, Up: Source Structures

6.1.5 Variable Declaration

A variable declaration looks like this: 

     var
       var_identifier: type_identifier;
       ...
       var_identifier: type_identifier;
or 
     var
       var_identifier: type_definition;
       ...
       var_identifier: type_definition;
and with initializing value: 
     var
       var_identifier: type_identifier value constant_expression;
       ...
       var_identifier: type_identifier value constant_expression;
or 
     var
       var_identifier: type_definition value constant_expression;
       ...
       var_identifier: type_definition value constant_expression;

A variable declaration part begins with the reserved word var. It declares a var_identifier whose type either can be specified by a type identifier, or by a type definion which either can be an array, a record, a set, a subrange, an enumerated type or a pointer to an type identifier. If value is specified followed by a constant expression satisfying the specified type, the variable declared is initialized with constant_expression. The reserved word value can be replaced by =, however value is not allowed in ISO-Pascal and Borland Pascal, and the replacement by = is not allowed in Extended Pascal.

See also

Type Definition, Type Declaration, Data Types, The Declaring Statement, Subroutine Parameter List Declaration

Node: Subroutine Declaration, Next: , Previous: Variable Declaration, Up: Source Structures

6.1.6 Subroutine Declaration

Node: The Procedure, Next: , Up: Subroutine Declaration

6.1.6.1 The Procedure

     procedure procedure_identifier;
     declaration_part
     begin
       statement_part
     end;
or with a parameter list: 
     procedure procedure_identifier (parameter_list);
     declaration_part
     begin
       statement_part
     end;

A procedure is quite like a sub-program: The declaration_part consists of label, constant, type, variable or subroutine declarations in free order. The statement_part consists of a sequence of statements. If parameter_list is specified, parameters can be passed to the procedure and can be used in statement_part. A recursive procedure call is allowed.

See also

The Function, Subroutine Parameter List Declaration

Node: The Function, Next: , Previous: The Procedure, Up: Subroutine Declaration

6.1.6.2 The Function

     function function_identifier: function_result_type;
     declaration_part
     begin
       statement_part
     end;
or with a parameter list: 
     function function_identifier (parameter_list): result_type;
     declaration_part
     begin
       statement_part
     end;

A function is a subroutine which has a return value of type function_result_type. It is structured like the program: the declaration_part consists of label, constant, type, variable or subroutine declarations in free order. The statement_part consists of a sequence of statements. If parameter_list is specified, parameters can be passed to the function and can be used in statement_part. The result is set via an assignment: 

     function_identifier := expression
Recursive function calls are allowed. Concerning the result type, ISO 7185 Pascal and Borland Pascal only allow the intrinsic types, subranges, enumerated types and pointer types to be returned. In Extended Pascal, function_result_type can be every assignable type. Of course, there are no type restrictions in GNU Pascal as well. If extended syntax is switched on, functions can be called like procedures via procedure call statement.

See also

The Procedure, Subroutine Parameter List Declaration, Data Types

Node: The Operator, Next: , Previous: The Function, Up: Subroutine Declaration

6.1.6.3 The Operator

GNU Pascal allows to define operators which can be used the infix style in expressions. For a more detailed description, see Operators

Node: Subroutine Parameter List Declaration, Previous: The Operator, Up: Subroutine Declaration

6.1.6.4 Subroutine Parameter List Declaration

     parameter; ...; parameter

Each parameter can start with a prefix (see below) describing how the parameters are passed, followed by a comma seperated list of one or more parameter_identifiers and an optional parameter_type. 

     procedure DoIt (var x, y, z: OneType; a, b: AnotherType; var q);

To understand parameter passing, first some definitions.

actual parameter
the parameter passed in to the routine.
formal parameter
the parameter as used inside the procedure.
by value
the value of the actual parameter is copied on to the stack.
by reference
the address of the actual parameter is copied on to the stack.
L-value
(left hand of a := statement) something that can be assigned to (not a constant, or const or protected variable or other immutable item).
R-value
(right hand of a := statement) anything you can get the value of (could be a constant, an expression, a variable (whether const or protected or not) or just about anything.
addressable
something you can get the address of (not a field of a packed structure or a variable with `attribute (register)' (GPC extension)).
aliasing
accessing memory via two different names (e.g. a global variable passed by reference to a procedure can be accessed either as the global variable or the formal paramater). Generally this is very bad practice.

Technical note: Parameters are not always passed on the stack, they may also be passed in registers, especially on RISC machines.

The prefix defines how a variable is passed on the stack and how you can access the formal_parameter inside the procedure. The prefix can be one of:

nothing 
          procedure DoIt (x: SomeType);

Technical: The actual parameter is passed by value or reference, but if passed by reference, it is then copied to a local copy on the stack. Aliasing has no effect on x.

What it means: you can modify x inside the routine, but your changes will not affect the actual parameter (and vice versa). The actual parameter can be a constant or other immutable object, or a protected or const variable.

protected 
          procedure DoIt (protected x: SomeType);

Technical: The actual parameter is passed by value or reference, but if passed by reference, it is then copied to a local copy on the stack. Aliasing has no effect on x. protected is a Extended Pascal extension.

What it means: if you modify the actual parameter, this will not affect x inside the routine. The actual parameter can be a constant or other immutable object, or a protected or const variable. You are forbidden from modifying x inside the routine.

var 
          procedure DoIt (var x: SomeType);

Technical: The actual parameter is passed by reference. Aliasing will definitely change x.

What it means: modifications to x inside the routine will change the actual parameter passed in. The actual parameter must be an addressable L-value (ie, it must be something you can take the address of and assign to).

A parameter of this kind is called variable parameter and internally corresponds to an L-value pointer (to the specified type identifier if any). This declaration is necessary if the parameter is to be modified within the routine and to hold its value still after return.

const 
          procedure DoIt (const x: SomeType);

Technical: The actual parameter is passed by value or reference. The compiler will make a copy of the actual parameter to have something it can address if the actual parameter is not addressable. You are forbidden from modifying x inside the routine, and therefore you cannot modify the actual parameter. Aliasing may or may not change x. const is a Borland Pascal extension.

What it means: You can pass any R-value. You cannot modify x inside the routine. If you change the actual parameter while inside the routine, x will have an undefined value.

protected var 
          procedure DoIt (protected var x: SomeType);

Technical: The actual parameter is passed by reference. The compiler will never make a copy of the actual parameter. You are forbidden from modifying x inside the routine, and therefore you cannot modify the actual parameter. Aliasing will definitely change x.

What it means: You can pass anything addressable. You cannot modify x inside the routine. If you change the actual parameter while inside the routine, x will change as well.

In GPC, the protected var mode guarantees that the parameter is always passed by reference, making it the correct choice for calling C routines with const pointer parameters.

If you omit the formal parameter type specification, then any type may be passed to that parameter. Generally this is a bad idea, but occasionally it can be useful, especially for low level code.

As an Extended Pascal extension, you can also declare procedural parameters directly: 

     procedure parameter_identifier
or: 
     function parameter_identifier: parameter_identifier_result_type

Example for parameter lists: 

     program ParameterDemo;
     
     procedure Foo (var Bar; var Baz: Integer; const Fred: Integer);
     
       procedure Glork1 (function Foo: Integer; procedure Bar (Baz: Integer));
       begin
         Bar (Foo)
       end;
     
     begin
       Baz := Integer (Bar) + Fred
     end;
     
     var
       a, b, c: Integer;
     
     begin
       Foo (a, b, c)
     end.

See also

Data Types, var, const, protected

Node: Statements, Next: , Previous: Subroutine Declaration, Up: Source Structures

6.1.7 Statements

Node: Assignment, Next: , Up: Statements

6.1.7.1 Assignment

The way an assignment looks like: 

     L-value := expression;

This statement assigns any valid expression to L-value. Make sure that the result of expression is compatible with L-value, otherwise an compilation error is reported. The := is called assignment operator. As long as L-value and expression are type compatible, they are assignment compatible for any definable type as well.

Node: begin end Compound Statement, Next: , Previous: Assignment, Up: Statements

6.1.7.2 begin end Compound Statement

It looks like that: 

     begin
       statement;
       statement;
       ...
       statement
     end

This statement joins several statements together into one compound statement which is treated as a single statement by the compiler. The finishing semicolon before end can be left out.

Node: if Statement, Next: , Previous: begin end Compound Statement, Up: Statements

6.1.7.3 if Statement

This statement has the following look: 

     if boolean_expression then
       statement
or with an alternative statement: 
     if boolean_expression then
       statement1
     else
       statement2

The if ... then statement consists of a boolean expression and a statement, which is conditionally executed if the evaluation of boolean_expression yields true.

If if ... then ... else is concerned, statement1 is executed depending on boolean_expression being true, otherwise statement2 is executed alternatively. Note: the statement before else must not finish with a semicolon.

Node: case Statement, Next: , Previous: if Statement, Up: Statements

6.1.7.4 case Statement

     case expression of
       selector: statement;
       ...
       selector: statement;
     end
or, with alternative statement sequence: 
     case ordinal_expression of
       selector: statement;
       ...
       selector: statement;
     otherwise                   { ``else'' instead of ``otherwise'' allowed }
       statement;
       ...
       statement;
     end
or, as part of the invariant record type definition: 
     type
       foo = record
         field_declarations
       case bar: variant_type of
         selector: (field_declarations);
         selector: (field_declarations);
         ...
       end;
or, without a variant selector field, 
     type
       foo = record
         field_declarations
       case variant_type of
         selector: (field_declarations);
         selector: (field_declarations);
         ...
       end;

The case statement compares the value of ordinal_expression to each selector, which can be a constant, a subrange, or a list of them separated by commas, being compatible with the result of ordinal_expression. Note: duplicate selectors or range crossing is not allowed unless {$borland-pascal} is specified. In case of equality the corresponding statement is executed. If otherwise is specified and no appropriate selector matched the expression, the series of statements following otherwise is executed. As a synonym for otherwise, else can be used. The semicolon before otherwise is optional.

@@ ???? The expression must match one of the selectors in order to continue, unless an alternative statement series is specified.

For case in a variant record type definition, see Record Types.

See also

if Statement

Node: for Statement, Next: , Previous: case Statement, Up: Statements

6.1.7.5 for Statement

For ordinal index variables: 

     for ordinal_variable := initial_value to final_value do
       statement
or 
     for ordinal_variable := initial_value downto final_value do
       statement

For sets: 

     for set_element_type_variable in some_set do
       statement

For pointer index variables: 

     for pointer_variable := initial_address to final_address do
       statement
or 
     for pointer_variable := initial_address downto final_address do
       statement

The for statement is a control statement where an index variable assumes every value of a certain range and for every value the index variable assumes statement is executed. The range can be specified by two bounds (which must be of the same type as the index variable, i.e. ordinal or pointers) or by a set.

For ordinal index variables:

For pointer index variables:

Since gpc provides a flat memory modell, all addresses are linear, so they can be compared. Still, such loops should be used (if at all) only for iterating through successive elements of an array.

For sets:

Please note: A modification of the index variable may result in unpredictable action.

See also

Set Types, Pointer Arithmetics, repeat Statement, for Statement

Node: while Statement, Next: , Previous: for Statement, Up: Statements

6.1.7.6 while Statement

The while loop has the following form 

     while boolean_expression do
       statement

The while statement declares a loop which is executed while boolean_expression is true. Since the terminating condition is checked before execution of the loop body, statement may never be executed.

See also

repeat Statement, for Statement

Node: repeat Statement, Next: , Previous: while Statement, Up: Statements

6.1.7.7 repeat Statement

     repeat
       statement;
       ...
       statement;
     until boolean_expression

The repeat ... until statement declares a loop which is repeated until boolean_expression is true. Since the terminating condition is checked after execution of the loop body, the statement sequence is executed at least once.

See also

while Statement, for Statement

Node: asm Inline, Next: , Previous: repeat Statement, Up: Statements

6.1.7.8 asm Inline

@@ ???? 

     asm (StatementList: String);

The asm inline statement is a GNU Pascal extension. It requires its parameter to be AT&T-noted assembler statements, and therefore it is not compatible with that one of Borland Pascal. statementlist is a string containing asm statements separated by semicolons.

Node: with Statement, Next: , Previous: asm Inline, Up: Statements

6.1.7.9 with Statement

Node: goto Statement, Next: , Previous: with Statement, Up: Statements

6.1.7.10 goto Statement

@@ ???? This statement looks like this: 

     goto label

(Under construction.)

Node: Procedure Call, Next: , Previous: goto Statement, Up: Statements

6.1.7.11 Procedure Call

     subroutine_name;

This statement calls the subroutine subroutine_name which can either be a procedure or, if GNU extended syntax is turned on, a function. In this case, the result is ignored.

Node: The Declaring Statement, Next: , Previous: Procedure Call, Up: Statements

6.1.7.12 The Declaring Statement

This statement allows to declare a variable within a statement part. It looks like this: 

     var
       var_identifier: type_identifier;
or 
     var
       var_identifier: type_definition;
and with initializing value: 
     var
       var_identifier: type_identifier value expression;
or 
     var
       var_identifier: type_definition value expression;

Unlike in declaration parts, the initializing expression does not have to be a constant expression. Note that every declaring statement has to start with var. The name space of the variable extends from its declaration to the end of the current matching statement sequence (which can be a statement part (of the program, a function, a procedure or an operator) or, within that part, a begin end compound statement, a repeat loop, or the else branch of a case statement). This statement is a GNU Pascal extension.

See also

Type Definition, Data Types

Node: Loop Control Statements, Previous: The Declaring Statement, Up: Statements

6.1.7.13 Loop Control Statements

These are 

     Continue;
and 
     Break;

These simple statements must not occur outside a loop, i.e. a for, while or repeat statement. Continue transfers control to the beginning of the loop right by its call, Break exits the current loop turn and continues loop execution.

Node: Modules and Units, Previous: Statements, Up: Source Structures

6.1.8 Import Part and Module/Unit Concept

Node: Modules, Next: , Up: Modules and Units

6.1.8.1 The Source Structure of ISO 10206 Extended Pascal Modules

@@ Description missing here

A module can have one or more export clauses and the name of an export clause doesn't have to be equal to the name of the module.

Sample module code with separate interface and implementation parts: 

     module DemoModule interface;  { interface part }
     
     export DemoModule = (FooType, SetFoo, GetFoo);
     
     type
       FooType = Integer;
     
     procedure SetFoo (f: FooType);
     function  GetFoo: FooType;
     
     end.
     
     module DemoModule implementation;  { implementation part }
     
     import
       StandardInput;
       StandardOutput;
     
     var
       Foo: FooType;
     
     { Note: the effect is the same as a `forward' directive would have:
       parameter lists and result types are not allowed in the
       declaration of exported routines, according to EP. In GPC, they
       are allowed, but not required. }
     procedure SetFoo;
     begin
       Foo := f
     end;
     
     function GetFoo;
     begin
       GetFoo := Foo
     end;
     
     to begin do
       begin
         Foo := 59;
         WriteLn ('Just an example of a module initializer. See comment below')
       end;
     
     to end do
       begin
         Foo := 0;
         WriteLn ('Goodbye')
       end;
     
     end.

Alternatively the module interface and implementation may be combined as follows: 

     module DemoMod2;  { Alternative method }
     
     export Catch22 = (FooType, SetFoo, GetFoo);
     
     type
       FooType = Integer;
     
     procedure SetFoo (f: FooType);
     function  GetFoo: FooType;
     
     end; { note: this `end' is required here, even if the
            module-block below would be empty. }
     
     var
       Foo: FooType;
     
     procedure SetFoo;
     begin
       Foo := f
     end;
     
     function GetFoo;
     begin
       GetFoo := Foo
     end;
     
     end.

Either one of the two methods may be used like this: 

     program ModuleDemo (Output);
     
     import DemoModule;
     
     begin
       SetFoo (999);
       WriteLn (GetFoo);
     end.
     
     program ModDemo2 (Output);
     
     import Catch22 in 'demomod2.pas';
     
     begin
       SetFoo (999);
       WriteLn (GetFoo);
     end.

Somewhat simpler GPC modules are also supported. Please note: This is not supported in the Extended Pascal standard.

This is a simpler module support that does not require exports, imports, module headers etc.

These non-standard simple GPC modules look like the following example. They do not have an export part, do not have a separate module-block, do not use import/export features.

Instead, you have to emulate the exporting/importing yourself using attribute and external name. 

     module DemoMod3;
     
     type
       FooType = Integer;
     
     var
       Foo: FooType;
     
     procedure SetFoo (f: FooType); attribute (name = 'SetFoo');
     begin
       Foo := f
     end;
     
     function GetFoo: FooType; attribute (name = 'GetFoo');
     begin
       GetFoo := Foo;
     end;
     
     end.
     
     program ModDemo3 (Output);
     
     {$L demomod3.pas}  { explicitly link module }
     
     { Manually do the "import" from DemoMod3 }
     type
       FooType = Integer;
     
     procedure SetFoo (f: FooType); external name 'SetFoo';
     function  GetFoo: FooType;     external name 'GetFoo';
     
     begin
       SetFoo (999);
       WriteLn (GetFoo)
     end.

Module initialization and finalization:

The to begin do module initialization and to end do module finalization constructs now work on every target.

By the way: The "GPC specific" module definition is almost identical to the PXSC standard. With an additional keyword `global' which puts a declaration into an export interface with the name of the module, it will be the same. @@This is planned.

Node: Units, Previous: Modules, Up: Modules and Units

6.1.8.2 The Source Structure of UCSD/Borland Pascal Units

A generic GNU Pascal unit looks like the following: 

     unit name;
     
     interface
     
     import_part
     
     interface_part
     
     implementation
     
     implementation_part
     
     initialization_part
     
     end.

The name of the unit should coincide with the name of the file with the extension stripped. (If not, you can tell GPC the file name with uses foo in 'bar.pas', see uses.)

The import_part is either empty or contains a uses clause to import other units. It may also consist of an ISO-style import specification. Note that the implementation part is not preceeded by a second import part in GPC (see import).

The interface_part consists of constant, type, and variable declarations, procedure and function headings which may be freely mixed.

The implementation_part is like the declaration part of a program, but the headers of procedures and functions may be abbreviated: Parameter lists and function results may be omitted for procedures and functions already declared in the interface part.

The initialization_part may be missing, or it may be a begin followed by one or more statements, such that the unit has a statement part between this begin and the final end. Alternatively, a unit may have ISO-style module initializers and finalizers, see to begin do, to end do.

Note that GPC does not yet check whether all interface declarations are resolved in the same unit. The implementation of procedures and functions which are in fact not used may be omitted, and/or procedures and functions may be implemented somewhere else, even in a different language. However, relying on a GPC bug (that will eventually be fixed) is not a good idea, so this is not recommended. Instead, declare such routines as external.

A unit exports everything declared in the interface section. The exported interface has the name of the unit and is compatible with Extended Pascal module interfaces since GPC uses the same code to handle both.

Node: Data Types, Next: , Previous: Source Structures, Up: Programming

6.2 Data Types

Node: Type Definition, Next: , Up: Data Types

6.2.1 Type Definition

As described in Type Declaration, a type declaration part looks like this: 

     type
        type_identifier = type_definition;
        ...
        type_identifier = type_definition;
where the left side is the type declaration and the right one the type definition side. GNU Pascal offers various possibilities to implement highly specialized and problem-specific data types.

Node: Ordinal Types, Next: , Previous: Type Definition, Up: Data Types

6.2.2 Ordinal Types

An ordinal type is one that can be mapped to a range of whole numbers. It includes integer types, character types, enumerated types and subrange types of them.

A character type is represented by the intrinsic type Char which can hold elements of the operating system's character set (usually ASCII). Conversion between character types and integer types is possible with the intrinsic functions Ord and Chr.

An enumerated type defines a range of elements which are referred to by identifiers. Conversion from enumerated types to integer types is possible with the intrinsic function Ord. Conversion from integer to ordinal types is only possible by type-casting or using the extended form of Succ. 

     var
       Foo: Char;       { foo can hold a character }
       Num: '0' .. '9'; { Can hold decimal digits, is a subrange type of Char }
       Day: (Monday, Tuesday, Wednesday, Thursday, Friday); { Can hold weekday }

See also

Ord, Chr, Type Casts

Node: Integer Types, Next: , Previous: Ordinal Types, Up: Data Types

6.2.3 Integer Types

Besides Integer, GNU Pascal supports a large zoo of integer types. Some of them you will find in other compilers, too, but most are GNU Pascal extensions, introduced for particular needs. Many of these types are synonyms for each other. In total, GPC provides 20 built-in integer types, plus seven families you can play with. (Four of these "families" are signed and unsigned, packed and unpacked subrange types; the others are explained below.)

See also: Subrange Types.

Node: Natural Integer Types, Next: , Up: Integer Types

6.2.3.1 The CPU's Natural Integer Types

For most purposes, you will always use Integer, a signed integer type which has the "natural" size of such types for the machine. On most machines GPC runs on, this is a size of 32 bits, so Integer usually has a range of -2147483648..2147483647 (see Integer).

If you need an unsigned integer type, the "natural" choice is Cardinal, also called Word. Like Integer, it has 32 bits on most machines and thus a range of 0..4294967295 (see Cardinal, Word).

These natural integer types should be your first choice for best performance. For instance on an IA32 CPU operations with Integer usually work faster than operations with shorter integer types like ShortInt or ByteInt (see below).

Node: Main Branch Integer Types, Next: , Previous: Natural Integer Types, Up: Integer Types

6.2.3.2 The Main Branch of Integer Types

Integer, Cardinal, and Word define the three "main branches" of GPC's integer types. You won't always be able to deal with the natural size; sometimes something smaller or longer will be needed. Especially when interfacing with libraries written in other languages such as C, you will need equivalents for their integer types.

The following variants of Integer, Cardinal and Word (plus one Boolean type) are guaranteed to be compatible to the integer types of GNU C. The sizes given, however, are not guaranteed. They are just typical values currently used on most platforms, but they may be actually shorter or increase in the future.

signed unsigned also unsigned GNU C equivalent size in bits (typically)
ByteInt ByteCard Byte [un]signed char 8
ShortInt ShortCard ShortWord [unsigned] short int 16
Integer Cardinal Word [unsigned] int 32
MedInt MedCard MedWord [unsigned] long int 32
LongInt LongCard LongWord [unsigned] long long int 64
-- SizeType -- size_t 32
PtrDiffType -- -- ptrdiff_t 32
PtrInt PtrCard PtrWord -- 32
-- CBoolean -- _Bool, bool 8

Since we don't know whether LongInt will always remain the "longest" integer type available - maybe GNU C will get long long long int, one day, which we will support as LongLongInt - we have added the synonym LongestInt for the longest available singed integer type, and the same holds for LongestCard and LongestWord.

Node: Integer Types with Specified Size, Next: , Previous: Main Branch Integer Types, Up: Integer Types

6.2.3.3 Integer Types with Specified Size

In some situations you will need an integer type of a well-defined size. For this purpose, GNU Pascal provides type attributes (see attribute). The type 

     Integer attribute (Size = 42)

is guaranteed to have a precision of 42 bits. In a realistic context, you will most often give a power of two as the number of bits, and the machine you will need it on will support variables of that size. If this is the case, the specified precision will simultaneously be the amount of storage needed for variables of this type.

In short: If you want to be sure that you have a signed integer with 32 bits width, write Integer attribute (Size = 32), not just Integer which might be bigger. The same works with unsigned integer types such as Cardinal and Word and with Boolean types.

This way, you can't get a higher precision than that of LongestInt or LongestCard (see Main Branch Integer Types). If you need higher precision, you can look at the GMP unit (see GMP) which provides integer types with arbitrary precision, but their usage is different from normal integer types.

Node: Integer Types and Compatibility, Next: , Previous: Integer Types with Specified Size, Up: Integer Types

6.2.3.4 Integer Types and Compatibility

If you care about ISO compliance, only use Integer and subranges of Integer.

Some of GPC's non-ISO integer types exist in Borland Pascal, too: Byte, ShortInt, Word, and LongInt. The sizes of these types, however, are not the same as in Borland Pascal. Even for Byte this is not guaranteed (while probable, though).

When designing GNU Pascal, we thought about compatibility to Borland Pascal. Since GNU Pascal is (at least) a 32-bit compiler, Integer must have (at least) 32 bits. But what to do with Word? Same size as Integer (like in BP) or 16 bits (like in BP)? We decided to make Word the "natural-sized" unsigned integer type, thus making it (at least) 32 bits wide. Similarly, we decided to give LongInt twice the size of Integer (like in BP) rather than making it 32 bits wide (like in BP). So LongInt has 64 bits, and ShortInt has 16 bits on the IA32 platform.

On the other hand, to increase compatibility to Borland Pascal and Delphi, GPC provides the alias name Comp for LongInt (64 bits on IA32) and SmallInt for ShortInt (16 bits on IA32). Note that BP treats Comp as a "real" type and allows assignments like MyCompVar := 42.0. Since we don't consider this a feature, GPC does not copy this behaviour.

Node: Summary of Integer Types, Previous: Integer Types and Compatibility, Up: Integer Types

6.2.3.5 Summary of Integer Types

Here is a summary of all integer types defined in GPC. The sizes and ranges are only typical values, valid on some, but not all platforms. Compatibility to GNU C however is guaranteed.

ByteInt
signed 8-bit integer type, -128..128,
compatible to signed char in GNU C.
Byte
unsigned 8-bit integer type, 0..255,
compatible to unsigned char in GNU C.
ShortInt
signed 16-bit integer type, -32768..32767,
compatible to short int in GNU C.
ShortWord
unsigned 16-bit integer type, 0..65535,
compatible to unsigned short int in GNU C.
Integer
signed 32-bit integer type, -2147483648..2147483647,
compatible to int in GNU C.
Word
unsigned 32-bit integer type, 0..4294967295,
compatible to unsigned int in GNU C.
MedInt
signed 32-bit integer type, -2147483648..2147483647,
compatible to long int in GNU C.
MedWord
unsigned 32-bit integer type, 0..4294967295,
compatible to unsigned long int in GNU C.
LongInt
signed 64-bit integer type, -9223372036854775808..9223372036854775807,
compatible to long long int in GNU C.
LongWord
unsigned 64-bit integer type, 0..18446744073709551615,
compatible to unsigned long long int in GNU C.
LongestInt
signed 64-bit integer type, -9223372036854775808..9223372036854775807.
LongestWord
unsigned 64-bit integer type, 0..18446744073709551615.
Comp
signed 64-bit integer type, -9223372036854775808..9223372036854775807.
SmallInt
signed 16-bit integer type, -32768..32767.
SizeType
integer type (usually unsigned) to represent the size of objects in memory
PtrDiffType
signed integer type to represent the difference between two positions in memory
PtrInt
signed integer type of the same size as a pointer
PtrWord
unsigned integer type of the same size as a pointer

To specify the number of bits definitely, use type attributes, attribute. 

     program IntegerTypesDemo (Output);
     
     var
       ByteVar: Byte;
       ShortIntVar: ShortInt;
       Foo: MedCard;
       Big: LongestInt;
     
     begin
       ShortIntVar := 1000;
       Big := MaxInt * ShortIntVar;
       ByteVar := 127;
       Foo := 16#deadbeef
     end.

See also: Subrange Types.

Node: Real Types, Next: , Previous: Integer Types, Up: Data Types

6.2.4 Built-in Real (Floating Point) Types

GPC has three built-in floating point types to represent real numbers. Each of them is available under two names (for compatibility to other compilers and languages).

For most purposes, you will always use Real which is the only one of them that is part of Standard and Extended Pascal. If memory constraints apply, you might want to choose ShortReal for larger arrays. On the other hand, if high precision is needed, you can use LongReal. When interfacing with libraries written in other languages such as C, you will need the equivalents for their real types.

Note that not all machines support longer floating point types, so LongReal is the same as Real on these machines. Also, some machines may support a longer type, but not do all arithmetic operations (e.g. the Sin function, Sin) in a precision higher than that of Real. If you need higher precision, you can look at the GMP unit (see GMP) which provides rational and real numbers with arbitrary precision, but their usage is different from normal real types.

The following real types are guaranteed to be compatible to the real types of GNU C. The sizes given, however, are not guaranteed. They are just typical values used on any IEEE compatible floating point hardware, but they may be different on some machines.

type name alternative name GNU C equivalent size in bits (typically)
ShortReal Single float 32
Real Double double 64
LongReal Extended long double 80

Node: String Types, Next: , Previous: Real Types, Up: Data Types

6.2.5 Strings Types

There are several ways to use strings in GNU Pascal. One of them is the use of the intrinsic string type String which is a predefined schema type. The schema discriminant of this type holds the maximal length, which is of type Integer, so values up to MaxInt can be specified. For String, an assignment is defined. There are many built-in functions and procedures for comfortable strings handling.

@@ ???? String procedures and functions.

Another way to use strings is to use arrays of type Char. For these, an intrinsic assignment is defined as well. Besides, String and Char are assignment compatible. The preferred way, however, is String because of the numerous possibilities for string handling.

Node: Character Types, Next: , Previous: String Types, Up: Data Types

6.2.6 Character Types

Character types are a special case of ordinal types.

See also

Ordinal Types, Chr, Ord, Pred, Succ.

Node: Enumerated Types, Next: , Previous: Character Types, Up: Data Types

6.2.7 Enumerated Types

     type
       enum_type_identifier = (identifier, ..., identifier);

An enumerated type is a a special case of ordinal types and defines a range of elements which are referred to by identifiers. Enumerated types are ordered by occurence in the identifier list. So, they can be used as index types in an array definition, and it is possible to define subranges of them. Since they are ordered, they can be compared to one another. The intrinsic function Ord applied to name_identifier returns the number of occurence in the identifier list (beginning with zero), Pred and Succ return the predecessor and successor of name_identifier. Boolean is a special case of an enumerated type.

See also

Ordinal Types, Array Types, Subrange Types, Ord, Boolean, Char, Pred, Succ.

Node: File Types, Next: , Previous: Enumerated Types, Up: Data Types

6.2.8 File Types

Files are used to store data permanently, normally on hard drives or floppies. There are tree types of files available: text files, typed and untyped files.

Text files are used to store text in them, where typed files are used to store many entries of the same type in them, e.g. addresses. Text files and typed files are accessible by Read and Write operations and do not need the parameter BlockSize in Reset or Rewrite. On the other hand, untyped files are used to store any type of information in them but you need to use BlockWrite or BlockRead to store or retrieve data out of this file. 

     var
       F1: Text;   { a textfile }
       F2: file of Real;   { a typed filed used to store real values in it }
       F3: File;   { an untyped file }

See also

File Routines, Write, Read, BlockRead, BlockWrite, Reset, Rewrite

Node: Boolean (Intrinsic), Next: , Previous: File Types, Up: Data Types

6.2.9 Boolean (Intrinsic)

The intrinsic Boolean represents boolean values, i.e. it can only assume true and false (which are predefined constants). This type corresponds to the enumerated type 

     type
       Boolean = (False, True);
Since it is declared this way, it follows: 
     Ord (False) = 0
     Ord (True) = 1
     False < True
There are four intrinsic logical operators. The logical and, or and not. In Borland Pascal and GNU Pascal, there is a logical "exclusive or" xor.

See also

Enumerated Types, and, or, not, xor

Node: Pointer (Intrinsic), Next: , Previous: Boolean (Intrinsic), Up: Data Types

6.2.10 Pointer (Intrinsic)

The intrinsic Pointer Type is a so-called unspecified or typeless pointer (i.e. a pointer which does not point to any type but holds simply a memory address).

See also

Pointer Types, nil

Node: Type Definition Possibilities, Next: , Previous: Pointer (Intrinsic), Up: Data Types

6.2.11 Type Definition Possibilities

Node: Subrange Types, Next: , Up: Type Definition Possibilities

6.2.11.1 Subrange Types

GNU Pascal supports Standard Pascal's subrange types: 

     program SubrangeDemo;
     type
       MonthInt = 1 .. 12;
       Capital = 'A' .. 'Z';
       ControlChar = ^A .. ^Z;  { `^A' = `Chr (1)' is a BP extension }
     begin
     end.
Also possible: Subranges of enumerated types: 
     program EnumSubrangeDemo;
     type
       { This is an enumerated type. }
       Days = (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
     
       { This is a subrange of `Days'. }
       Working = Mon .. Fri;
     
     begin
     end.

To increase performance, variables of such a type are aligned in a way which makes them fastest to access by the CPU. As a result, 1 .. 12 occupies 4 bytes of storage on an IA32 CPU.

For the case you want to save storage at the expense of speed, GPC provides a packed variant of these as an extension: 

     program PackedSubrangeDemo;
     type
       MonthInt = packed 1 .. 12;
     begin
     end.

A variable of this type occupies the shortest possible (i.e., addressable) space in memory - one byte on an IA32 compatible CPU.

See also: packed.

Node: Array Types, Next: , Previous: Subrange Types, Up: Type Definition Possibilities

6.2.11.2 Array Types

     type
       array_type_identifier = array [index_type] of element_type
or 
     type
       array_type_identifier = array [index_type, ..., index_type] of element_type

The reserved word array defines an array type. index_type has to be an ordinal type, subrange type or an enumerated type, where several index types, separated by commas, are allowed. element_type is an arbitrary type. An element of an array is accessed by array_type_variable [index_number]. The upper and lower index bounds can be determined by the intrinsic functions High and Low. 

     type
       IntArray = array [1 .. 20] of Integer;
       Foo      = array [(Mo, Tu, We, Th, Fr, Sa, Su)] of Char;
       Bar      = array [0 .. 9, 'a' .. 'z', (Qux, Glork1, Fred)] of Real;
       Baz1     = array [1 .. 10] of IntArray;
       { equal (but declared differently): }
       Baz2     = array [1 .. 10, 1 .. 20] of Integer;

See also

High, Low

Node: Record Types, Next: , Previous: Array Types, Up: Type Definition Possibilities

6.2.11.3 Record Types

     type
       record_type_identifier = record
         field_identifier: type_definition;
         ...
         field_identifier: type_definition;
       end;

or, with a variant part, 

     type
       record_type_identifier = record
         field_identifier: type_definition;
         ...
         field_identifier: type_definition;
       case bar: variant_type of
         selector: (field_declarations);
         selector: (field_declarations);
         ...
       end;

or, without a variant selector field, 

     type
       record_type_identifier = record
         field_identifier: type_definition;
         ...
         field_identifier: type_definition;
       case variant_type of
         selector: (field_declarations);
         selector: (field_declarations);
         ...
       end;

The reserved word record defines a structure of fields. Records can be packed to save memory usage at the expense of speed.

The reserved word record and record types are defined in ISO 7185 Pascal. According to ISO Pascal, the variant type must be an identifier. GNU Pascal, like UCSD and Borland Pascal, also allows a subrange here.

A record field is accessed by record_type_variable . field_identifier

See also: packed, case Statement.

Node: Variant Records, Next: , Previous: Record Types, Up: Type Definition Possibilities

6.2.11.4 Variant Records

GPC supports variant records like in EP and BP. The following construction is not allowed in Extended Pascal, but in BP and GPC: 

     program BPVariantRecordDemo;
     
     type
       PersonRec = record
         Age: Integer;
       case EyeColor: (Red, Green, Blue, Brown) of
         Red, Green : (WearsGlasses: Boolean);
         Blue, Brown: (LengthOfLashes: Integer);
       end;
     
     begin
     end.

In EP, the variant field needs a type identifier, which, of course, also works in GPC: 

     program EPVariantRecordDemo;
     
     type
       EyeColorType = (Red, Green, Blue, Brown);
     
       PersonRec = record
         Age: Integer;
       case EyeColor: EyeColorType of
         Red, Green : (WearsGlasses: Boolean);
         Blue, Brown: (LengthOfLashes: Integer);
       end;
     
     begin
     end.

Node: Schema Types, Next: , Previous: Variant Records, Up: Type Definition Possibilities

6.2.11.5 EP's Schema Types including String

Schemata are types that depend on one or more variables, called discriminants. They are an ISO 10206 Extended Pascal feature. 

     type
       RealArray (n: Integer) = array [1 .. n] of Real;
       Matrix (n, m: PositiveInteger) = array [1 .. n, 1 .. m] of Integer;

The type RealArray in this example is called a Schema with the discriminant n.

To declare a variable of such a type, write: 

     var
       Foo: RealArray (42);

The discriminants of every global or local schema variable are initialized at the beginning of the procedure, function or program where the schema variable is declared.

Schema-typed variables "know" about their discriminants. Discriminants can be accessed just like record fields: 

     program Schema1Demo;
     type
       PositiveInteger = 1 .. MaxInt;
       RealArray (n: Integer) = array [1 .. n] of Real;
       Matrix (n, m: PositiveInteger) = array [1 .. n, 1 .. m] of Integer;
     
     var
       Foo: RealArray (42);
     
     begin
       WriteLn (Foo.n)  { yields 42 }
     end.

Schemata may be passed as parameters. While types of schema variables must always have specified discriminants (which may be other variables), formal parameters (by reference or by value) may be of a schema type without specified discriminant. In this, the actual parameter may posses any discriminant. The discriminants of the parameters get their values from the actual parameters.

Also, pointers to schema variables may be declared without a discriminant: 

     program Schema2Demo;
     type
       RealArray (n: Integer) = array [1 .. n] of Real;
       RealArrayPtr = ^RealArray;
     var
       Bar: RealArrayPtr;
     begin
     end.

When applying New to such a pointer, you must specify the intended value of the discriminant as a parameter: 

     New (Bar, 137)

As a GNU Pascal extension, the above can also be written as 

     Bar := New (RealArrayPtr, 137)

The allocated variable behaves like any other schema variable: 

     program Schema3Demo;
     type
       RealArray (n: Integer) = array [1 .. n] of Real;
       RealArrayPtr = ^RealArray;
     var
       Bar: RealArrayPtr;
       i: Integer;
     begin
       Bar := New (RealArrayPtr, 137);
       for i := 1 to Bar^.n do
         Bar^[i] := 42
     end.

Since the schema variable "knows" its size, pointers to schemata can be disposed just like other pointers: 

     Dispose (Bar)

Schemata are not limited to arrays. They can be of any type that normally requires constant values in its definition, for instance subrange types, or records containing arrays etc. (Sets do not yet work.)

References to the schema discriminants are allowed, and the with statement is also allowed, so one can say: 

     program SchemaWithDemo;
     type
       RealArray (n: Integer) = array [1 .. n] of Real;
     var
       MyArray: RealArray (42);
     begin
       WriteLn (MyArray.n);  { writes 42 }
       with MyArray do
         WriteLn (n);        { writes 42 }
     end.

Finally, here is a somewhat exotic example. Here, a ColoredInteger behaves just like an ordinary integer, but it has an additional property Color which can be accessed like a record field. 

     program SchemaExoticDemo;
     
     type
       ColorType = (Red, Green, Blue);
       ColoredInteger (Color: ColorType) = Integer;
     
     var
       Foo: ColoredInteger (Green);
     
     begin
       Foo := 7;
       if Foo.Color = Red then
         Inc (Foo, 2)
       else
         Foo := Foo div 3
     end.

An important schema is the predefined String schema (according to Extended Pascal). It has one predefined discriminant identifier Capacity. GPC implements the String schema as follows: 

     type
       String (Capacity: Cardinal) = record
         Length: 0 .. Capacity;
         Chars: packed array [1 .. Capacity + 1] of Char
       end;

The Capacity field may be directly referenced by the user, the Length field is referenced by a predefined string function Length (Str) and contains the current string length. Chars contains the chars in the string. The Chars and Length fields cannot be directly referenced by a user program.

If a formal value parameter is of type String (with or without discriminant), the actual parameter may be either a String schema, a fixed string (character array), a single character, a string literal or a string expression. If the actual parameter is a String schema, it is copied for the parameter in the usual way. If it is not a schema, a String schema is created automatically, the actual parameter is copied to the new variable and the Capacity field of the new variable is set to the length of the actual parameter.

Actual parameters to var parameters of type String must be String schemata, not string literals or character arrays. 

     program StringDemo (Output);
     
     type
       SType = String (10);
       SPtr  = ^String;
     
     var
       Str : SType;
       Str2: String (100000);
       Str3: String (20) value 'string expression';
       DStr: ^String;
       ZStr: SPtr;
       Len : Integer value 256;
       Ch  : Char value 'R';
     
     { `String' accepts any length of strings }
     procedure Foo (z: String);
     begin
       WriteLn ('Capacity: ', z.Capacity);
       WriteLn ('Length  : ', Length (z));
       WriteLn ('Contents: ', z);
     end;
     
     { Another way to use dynamic strings }
     procedure Bar (SLen: Integer);
     var
       LString: String (SLen);
       FooStr: type of LString;
     begin
       LString := 'Hello world!';
       Foo (LString);
       FooStr := 'How are you?';
       Foo (FooStr);
     end;
     
     begin
       Str  := 'KUKKUU';
       Str2 := 'A longer string variable';
       New (DStr, 1000);  { Select the string Capacity with `New' }
       DStr^ := 'The maximum length of this is 1000 chars';
       New (ZStr, Len);
       ZStr^ := 'This should fit here';
       Foo (Str);
       Foo (Str2);
       Foo ('This is a constant string');
       Foo ('This is a ' + Str3);
       Foo (Ch);  { A char parameter to string routine }
       Foo ('');  { An empty string }
       Foo (DStr^);
       Foo (ZStr^);
       Bar (10000);
     end.

In the above example, the predefined procedure New was used to select the capacity of the strings. Procedure Bar also has a string whose size depends of the parameter passed to it and another string whose type will be the same as the type of the first string, using the type of construct.

All string and character types are compatible as long as the destination string is long enough to hold the source in assignments. If the source string is shorter than the destination, the destination is automatically blank padded if the destination string is not of string schema type.

Node: Set Types, Next: , Previous: Schema Types, Up: Type Definition Possibilities

6.2.11.6 Set Types

     set_type_identifier = set of set_element_type;

set_type_identifier is a set of elements from set_element_type which is either an ordinal type, an enumerated type or a subrange type. Set element representatives are joined together into a set by brackets: 

     [set_element, ..., set_element]
[] indicates the empty set, which is compatible with all set types. Note: Borland Pascal restricts the maximal set size (i.e. the range of the set element type) to 256, GNU Pascal has no such restriction. The number of elements a set variable is holding can be determined by the intrinsic set function Card (which is a GNU Pascal extension, in Extended Pascal and Borland Pascal you can use SizeOf instead but note the element type size in bytes, then) to the set. There are four intrinsic binary set operations: the union +, the intersection * and the difference -. The symmetric difference >< is an Extended Pascal extension.

See also

Card, SizeOf

Node: Pointer Types, Next: , Previous: Set Types, Up: Type Definition Possibilities

6.2.11.7 Pointer Types

     pointer_type_identifier = ^type_identifier;

A pointer of the type pointer_type_identifier holds the address at which data of the type type_identifier is situated. Unlike other identifier declarations, where all identifiers in definition part have to be declared before, in a pointer type declaration type_identifier may be declared after pointer_type_identifier. The data pointed to is accessed by pointer_type_variable^. To mark an unassigned pointer, the nil constant (which stands for "not in list") has to be assigned to it, which is compatible with all pointer types. 

     type
       ItselfFoo = ^ItselfFoo;  { possible but mostly senseless }
     
       PInt      = ^Integer;    { Pointer to an Integer }
     
       PNode     = ^TNode;      { Linked list }
       TNode     = record
         Key     : Integer;
         NextNode: PNode;
       end;
     
     var
       Foo, Bar: PInt;
     
     begin
       Foo := Bar;  { Modify address which foo is holding }
       Foo^ := 5;   { Access data foo is pointing to }
     end.

GPC also suports pointers to procedures or function and calls through them. This is a non-standard feature. 

     program ProcPtrDemo (Output);
     
     type
       ProcPtr = ^procedure (i: Integer);
     
     var
       PVar: ProcPtr;
     
     procedure WriteInt (i: Integer);
     begin
       WriteLn ('Integer: ', i : 1)
     end;
     
     begin
       { Let PVar point to function WriteInt }
       PVar := @WriteInt;
     
       { Call the function by dereferencing the function pointer }
       PVar^ (12345)
     end.

See also: Pointer (Intrinsic).

Node: Procedural Types, Next: , Previous: Pointer Types, Up: Type Definition Possibilities

6.2.11.8 Procedural and Functional Types

For procedures without a parameter list: 

     procedure_type_identifier = procedure name_identifier;
or functions: 
     function_type_identifier =
            function name_identifier: function_result_type;

For procedures with a parameter list: 

     procedure_type_identifier =
            procedure name_identifier (parameter_list);
or functions: 
     function_type_identifier =
            function name_identifier (parameter_list): function_result_type;

Procedural types can be used as procedures or functions respectively, but also a value can be assigned to them. Procedural types are a Borland Pascal extension. In Borland Pascal, function_result_type can only be one of these types: ordinal types, real types, pointer types, the intrinsic String type. In GNU Pascal every function result type for procedural types is allowed.

BP has procedural and functional types: 

     type
       CompareFunction = function (Key1, Key2: String): Integer;
     
     function Sort (Compare: CompareFunction);
     begin
       ...
     end;

Standard Pascal has procedural and functional parameters: 

     function Sort (function Compare (Key1, Key2: String): Integer);
     begin
       ...
     end;

Both ways have pros and cons, e.g. in BP you can save, compare, trade, etc. procedural values, or build arrays of them, while the SP way does not require a type declaration and prevents problems with uninitialized or invalid pointers (which in BP will usually crash the program).

GPC supports both ways. An important feature of Standard Pascal (but not BP) that GPC also supports is the possibility to pass local routines as procedural or functional parameters, even if the called routine is declared far remote. The called routine can then call the passed local routine and it will have access to the original caller's local variables. 

     program LocalProceduralParameterDemo;
     
     procedure CallProcedure (procedure Proc);
     begin
       Proc
     end;
     
     procedure MainProcedure;
     var LocalVariable: Integer;
     
       procedure LocalProcedure;
       begin
         WriteLn (LocalVariable)
       end;
     
     begin
       LocalVariable := 42;
       CallProcedure (LocalProcedure)
     end;
     
     begin
       MainProcedure
     end.

See also: The Procedure, The Function, Subroutine Parameter List Declaration, Procedure Call.

Node: Object Types, Next: , Previous: Procedural Types, Up: Type Definition Possibilities

6.2.11.9 Object Types

Object types are used to encapsulate data and methods. Furthermore, they implement a mechanism for inheritance.

See also

OOP

Node: Type Initializers, Next: , Previous: Object Types, Up: Type Definition Possibilities

6.2.11.10 Initial values to type denoters

A type may be initialized to a value of expression when it is declared, like a variable, as in: 

     program TypeVarInitDemo;
     type
       Int10   = Integer value 10;
       FooType = Real;
       MyType  = Char value Pred ('A');
       EType   = (a, b, c, d, e, f, g) value d;
     
     const
       Answer = 42;
     
     var
       ii : Int10;                    { Value of ii set to 10 }
       ch : MyType  value Pred ('z');
       aa : Integer value Answer + 10;
       foo: FooType value Sqr (Answer);
       e1 : EType;                    { value set to d }
       e2 : EType value g;            { value set to g }
     begin
     end.

Extended Pascal requires the type initializers to be constant expressions. GPC allows any valid expression.

Note, however, that the expressions that affect the size of storage allocated for objects (e.g. the length of arrays) may contain variables only inside functions or procedures.

GPC evaluates the initial values used for the type when an identifier is declared for that type. If a variable is declared with a type-denoter that uses a type-name which already has an initial value the latter initialization has precedence.

@@ GPC does not know how to calculate constant values for math functions in the runtime library at compile time, e.g. Exp (Sin (2.4567)), so you should not use these kind of expressions in object size expressions. (Extended Pascal allows this.)

Node: Restricted Types, Previous: Type Initializers, Up: Type Definition Possibilities

6.2.11.11 Restricted Types

GPC supports restricted types, defined in Extended Pascal. A value of a restricted type may be passed as a value parameter to a formal parameter possessing its underlying type, or returned as the result of a function. A variable of a restricted type may be passed as a variable parameter to a formal parameter possessing the same type or its underlying type. No other operations, such as accessing a component of a restricted type value or performing arithmetic, are possible. 

     program RestrictedDemo;
     
     type
       UnrestrictedRecord = record
         a: Integer;
       end;
       RestrictedRecord = restricted UnrestrictedRecord;
     
     var
       r1: UnrestrictedRecord;
       r2: RestrictedRecord;
       i: restricted Integer;
       k: Integer;
     
     function AccessRestricted (p: UnrestrictedRecord): RestrictedRecord;
     var URes: UnrestrictedRecord;
     begin
       { The parameter is treated as unrestricted, even though the actual
         parameter may be restricted }
       URes.a := p.a;
       { It is allowed to assign a function result }
       AccessRestricted := URes;
     end;
     
     begin
       r1.a := 354;
     
       { Assigning a restricted function result to a restricted variable }
       { @@ Verify if this should really be allowed????? }
       r2 := AccessRestricted (r1);
     
       { Passing a restricted value to unrestricted formal parameter is ok }
       r2 := AccessRestricted (r2);
     
       {$ifdef BUG}
       { *** The following statements are not allowed *** }
       k := r2.a;      { field access (reading) }
       r2.a := 100;    { field access (writing) }
       r1 := r2;       { assignment source is restricted }
       r2 := r1;       { assignment target is restricted }
       r1 := AccessRestricted (r2); { assigning a restricted function
                                      result to an unrestricted object }
       i  := 16#ffff;  { assignment target is restricted }
       k  := i + 2;    { arithmetic with restricted value }
       {$endif}
     end.

Node: Machine-dependencies in Types, Previous: Type Definition Possibilities, Up: Data Types

6.2.12 Machine-dependencies in Types

Node: Endianness, Next: , Up: Machine-dependencies in Types

6.2.12.1 Endianness

Endianness means the order in which the bytes of a value larger than one byte are stored in memory. This affects, e.g., integer values and pointers while, e.g., arrays of single-byte characters are not affected. The GPC String schema, however, contains Capacity and Length fields before the character array. These fields are integer values larger than one byte, so the String schema is affected by endianness.

Endianness depends on the hardware, especially the CPU. The most common forms are:

Note: There are processors which can run in both little-endian and big-endian mode, e.g. the MIPS processors. A single program, however, (unless it uses special machine code instructions) will always run in one endianness.

Under normal circumstances, programs do not need to worry about endianness, the CPU handles it by itself. Endianness becomes important when exchanging data between different machines, e.g. via binary files or over a network. To avoid problems, one has to choose the endianness to use for the data exchange. E.g., the Internet uses big-endian data, and most known data formats have a specified endianness (usually that of the CPU on which the format was originally created). If you define your own binary data format, you're free to choose the endianness to use.

To deal with endianness, GPC predefines the symbol __BYTES_LITTLE_ENDIAN__ on little-endian machines and __BYTES_BIG_ENDIAN__ on big-endian machines. Besides, the Run Time System defines the constant BytesBigEndian as False on little-endian machines and True on big-endian machines.

There are also the symbols __BITS_LITTLE_ENDIAN__, __BITS_BIG_ENDIAN__, __WORDS_LITTLE_ENDIAN__, __WORDS_BIG_ENDIAN__ and the constants BitsBigEndian and WordsBigEndian which concern the order of bits within a byte (e.g., in packed records) or of words within multiword-numbers, but these are usually less important.

The Run Time System also contains a number of routines to convert endianness and to read or write data from/to binary files in a given endianness, independent of the CPU's endianness. These routines are described in the RTS reference (see Run Time System), under endianness. The demo program endiandemo.pas contains an example on how to use these routines.

Node: Alignment, Previous: Endianness, Up: Machine-dependencies in Types

6.2.12.2 Alignment

(Under construction.) @@ ????

Node: Operators, Next: , Previous: Data Types, Up: Programming

6.3 Operators

GNU Pascal supports all operators of ISO Pascal and Borland Pascal. In addition, you can define your own operators according to the Pascal-SC (PXSC) syntax.

Node: Built-in Operators, Next: , Up: Operators

6.3.1 Built-in Operators

The following table lists all built-in GNU Pascal operators, ordered by precedence: < etc. have the lowest precedence, not etc. the highest. As usual, the precedence of operators can be superseded with parentheses.

In an assignment statement, := has lower precedence than all operators. (This is rather obvious from the syntax of assignment statements, and is merely noted for programmers familiar with C where = is an operator.) 

     <    =    >    in   <>   >=   <=
     +    -    or   +<   -<   +>   ->
     *    /    div  mod  and  shl  shr  xor  *<   /<   *>   />
     pow  **   ><
     not  &    @

The Pascal-SC (PXSC) operators +<, -<, +>, ->, *<, /<, *>, and /> are not yet implemented into GNU Pascal but may be defined by the user (see below).

Node: User-defined Operators, Previous: Built-in Operators, Up: Operators

6.3.2 User-defined Operators

GNU Pascal allows the (re-)definition of binary operators according to the Pascal-SC (PXSC) syntax. The following vector addition example illustrates how to do this: 

     program OperatorDemo;
     
     type
       Vector3 = record
         x, y, z: Real;
       end;
     
     var
       a, b, c: Vector3 = (1, 2, 3);
     
     operator + (u, v: Vector3) w: Vector3;
     begin
       w.x := u.x + v.x;
       w.y := u.y + v.y;
       w.z := u.z + v.z;
     end;
     
     begin
       c := a + b
     end.

Between the closing parenthesis of the argument list and the result variable (w in the above example), GPC allows an optional equal sign. This is not allowed in PXSC, but it is consistent with Extended Pascal's function result variable definitions, where the equal sign is obligatory (but also optional in GPC).

The argument types needn't be equal, and the name of the operator may be an identifier instead of a known symbol. You cannot define new symbols in GPC.

The PXSC operators +>, +<, etc. for exact numerical calculations currently are not implemented in GPC, but you can define them. Also, the other real-type operators do not meet the requirements of PXSC; a module which fixes that would be a welcome contribution.

Node: Parameters, Next: , Previous: Operators, Up: Programming

6.4 Procedure And Function Parameters

Node: Protected Parameters, Next: , Up: Parameters

6.4.1 Parameters declared as protected or const

All the following works in GPC: 

     procedure Foo (protected a, b, c: Integer);    { 3 arguments }
     procedure Foo (a, b, c, protected: Integer);   { 4 arguments }
     procedure Foo (a, b, protected, c: Integer);   { 4 arguments }
     procedure Foo (protected: Integer);            { 1 argument  }
     procedure Foo (var protected: Integer);        { 1 argument  }
     procedure Foo (protected protected: Integer);  { 1 argument  }

Furthermore, GPC supports const, according to BP, which is equivalent to either protected or protected var, up to the compiler's discretion.

Node: Conformant Arrays, Next: , Previous: Protected Parameters, Up: Parameters

6.4.2 The Standard way to pass arrays of variable size

@@ (Under construction.)

A feature of Standard Pascal level 1.

Node: Open Arrays, Previous: Conformant Arrays, Up: Parameters

6.4.3 BP's alternative to Conformant Arrays

Borland Pascal "open array" formal parameters are implemented into GPC. Within the function body, they have integer type index with lower bound 0.

In constrast to conformant arrays (which are not supported by BP), open arrays allow any ordinal type as the index of the actual parameter (which is useful, e.g., if you want to be able to pass values of any enumeration type). However, they lose information about the lower bound (which is a problem, e.g., if you want to return information to the caller that relates to the actual array index, like the function IOSelect in the Run Time System does).

Node: String Slice Access, Next: , Previous: Pointer Arithmetics, Up: Programming

6.5 Accessing parts of strings (and other arrays)

GPC allows the access of parts ("slices") of strings as defined in Extended Pascal. For example: 

     program StringSliceDemo;
     
     const
       HelloWorld = 'Hello, world!';
     
     begin
       WriteLn (HelloWorld[8 .. 12])  { yields `world' }
     end.

As an extension, it also allows write access to a string slice: 

     program SliceWriteDemo;
     
     var
       s: String (42) = 'Hello, world!';
     
     begin
       s[8 .. 12] := 'folks';
       WriteLn (s)  { yields `Hello, folks!' }
     end.

As a further extension, GPC allows slice access also to non-string arrays. However, the usefulness of this feature is rather limited because of Pascal's strict type checking rules: If you have, e.g., an array [1 .. 10] of Integer and take a slice [1 .. 5] of it, it will not be compatible to another array [1 .. 5] of Integer because distinct array types are not compatible in Pascal, even if they look the same.

However, array slice access can be used in connection with conformant or open array parameters. See the program arrayslicedemo.pas (in the demos directory) for an example.

Node: Pointer Arithmetics, Next: , Previous: Parameters, Up: Programming

6.6 Pointer Arithmetics

GPC allows to increment, decrement, compare, and subtract pointers or to use them in for loops just like the C language.

GPC implements the address operator @ (a Borland Pascal extension). 

     program PointerArithmeticDemo;
     var
       a: array [1 .. 7] of Char;
       p, q: ^Char;
       i: Integer;
     
     {$X+}  { We need extended syntax for pointer arithmetic }
     
     begin
       for p := @a[1] to @a[7] do
         p^ := 'x';
     
       p := @a[7];
       q := @a[3];
       while p > q do
         begin
           p^ := 'y';
           Dec (p)
         end;
     
       p := @a[7];
       q := @a[3];
       i := q - p;    { yields 4 }
     end.

Incrementing a pointer by one means to increment the address it contains by the size of the variable it is pointing to. For typeless pointers (Pointer), the address is incremented by one instead.

Similar things hold when decrementing a pointer.

Subtracting two pointers yields the number of variables pointed to between both pointers, i.e. the difference of the addresses divided by the size of the variables pointed to. The pointers must be of the same type.

Node: Type Casts, Next: , Previous: String Slice Access, Up: Programming

6.7 Type Casts

In some cases, especially in low-level situations, Pascal's strong typing can be an obstacle. To temporarily circumvent this, GPC defines explicit "type casts" in a Borland Pascal compatible way.

There are two kinds of type casts, value type casts and variable type casts.

Value type casts

To convert a value of one data type into another type, you can use the target type like the name of a function that is called. The value to be converted can be a variable or an expression. Both the value's type and the destination type must be ordinal or pointer types. The ordinal value (extended to pointers to mean the address) is preserved in the cast.

An example: 

     program TypeCastDemo;
     
     var
       Ch: Char;
       i: Integer;
     
     begin
       i := Integer (Ch)
     end.

Another, more complicated, example: 

     program TypeCst2Demo;
     
     type
       CharPtr = ^Char;
       CharArray = array [0 .. 99] of Char;
       CharArrayPtr = ^CharArray;
     
     var
       Foo1, Foo2: CharPtr;
       Bar: CharArrayPtr;
     
     {$X+} { We need extended syntax in order to use ``Succ'' on a pointer }
     
     begin
       Foo1 := CharPtr (Bar);
       Foo2 := CharPtr (Succ (Bar))
     end.

However, because of risks involved with type casts, explained below, and because type-casts are non-standard, you should try to avoid type casts whenever possible - and it should be possible in most cases. For instance, the first example above could use the built-in function "Ord" instead of the type cast: 

     i := Ord (Ch);

The assignments in the second example could be written in the following way without any type casts: 

     Foo1 := @Bar^[0];
     Foo2 := @Bar^[1];

Note: In the case of pointers, a warning is issued if the dereferenced target type requires a bigger alignment than the dereferenced source type (see Alignment).

Variable type casts

It is also possible to temporarily change the type of a variable (more generally, any "lvalue", i.e. something whose address can be taken), without converting its contents in any way. This is called variable type casting.

The syntax is the same as for value type casting. The type-casted variable is still the same variable (memory location) as the original one, just with a different type. Outside of the type cast, the variable keeps its original type.

There are some important differences between value and variable type casting:

There are cases where a type-cast could be either a value or a variable cast. This is when both types are ordinal or pointer, and of the same size, and the value is an lvalue. Fortunately, in those cases, the results of both forms are the same, since the same ordinal values (or pointer addresses) are represented by the same bit patterns (when of the same size). Therefore, it doesn't matter which form of type-casting is actually used in these cases.

When dealing with objects (see OOP), it is sometimes necessary to cast a polymorphic pointer to an object into a pointer to a more specialized (derived) object (after checking the actual type). However, the as operator is a safer approach, so type-casts should be used there only for backward-compatibility (e.g., to BP).

See also: absolute, Alignment, Endianness, OOP, Ord, Chr, Round, Trunc.

Node: OOP, Next: , Previous: Type Casts, Up: Programming

6.8 Object-Oriented Programming

GNU Pascal follows the object model of Borland Pascal 7.0. The BP object extensions are almost fully implemented into GPC. This includes inheritance, virtual and non-virtual methods, constructors, destructors, pointer compatibility, extended `New' syntax (with constructor call and/or as a Boolean function), extended `Dispose' syntax (with destructor call).

The Borland object model is different from the ISO draft, but it will not be too difficult now to implement that too (plus the Borland Delphi Object Extensions which are quite similar to the ISO draft).

The syntax for an object type declaration is as follows: 

     program ObjectDemo;
     
     type
       Str100 = String (100);
     
       FooParentPtr = ^FooParent;
       FooPtr = ^Foo;
     
       FooParent = object
         constructor Init;
         destructor Done; virtual;
         procedure Bar (c: Real); virtual;
         function Baz (b, a, z: Char): Str100;  { not virtual }
       end;
     
       Foo = object (FooParent)
         x, y: Integer;
         constructor Init (a, b: Integer);
         destructor Done; virtual;
         procedure Bar (c: Real); virtual;  { overrides `FooParent.Bar' }
         z: Real;  { GPC extension: data fields after methods }
         function Baz: Boolean;  { new function }
       end;
     
     constructor FooParent.Init;
     begin
       WriteLn ('FooParent.Init')
     end;
     
     destructor FooParent.Done;
     begin
       WriteLn ('I''m also done.')
     end;
     
     procedure FooParent.Bar (c: Real);
     begin
       WriteLn ('FooParent.Bar (', c, ')')
     end;
     
     function FooParent.Baz (b, a, z: Char) = s: Str100;
     begin
       WriteStr (s, 'FooParent.Baz (', b, ', ', a, ', ', z, ')')
     end;
     
     constructor Foo.Init (a, b: Integer);
     begin
       inherited Init;
       x := a;
       y := b;
       z := 3.4;
       FooParent.Bar (1.7)
     end;
     
     destructor Foo.Done;
     begin
       WriteLn ('I''m done.');
       inherited Done
     end;
     
     procedure Foo.Bar (c: Real);
     begin
       WriteLn ('Foo.Bar (', c, ')')
     end;
     
     function Foo.Baz: Boolean;
     begin
       Baz := True
     end;
     
     var
       Ptr: FooParentPtr;
     
     begin
       Ptr := New (FooPtr, Init (2, 3));
       Ptr^.Bar (3);
       Dispose (Ptr, Done);
       New (Ptr, Init);
       with Ptr^ do
         WriteLn (Baz ('b', 'a', 'z'))
     end.

Remarks:

A pointer to FooParent may be assigned the address of a Foo object. A FooParent formal var parameter may get a Foo object as the actual parameter. In such cases, a call to a virtual method calls the child's method, whereas a call to a non-virtual method selects the parent's one: 

     var
       MyFooParent: FooParentPtr;
       SomeFoo: Foo;
     
     [...]
     
       SomeFoo.Init (4, 2);
       MyFooParent := @SomeFoo;
       MyFooParent^.bar (3.14);  { calls `foo.bar' }
       MyFooParent^.baz ('b', 'a', 'z');  { calls `fooParent.baz' }
       if SomeFoo.baz then  { calls `foo.baz' }
         WriteLn ('Baz!');

In a method, an overwritten method of a parent object can be called either prefixing it with the parent type name, or using the keyword inherited: 

     procedure Foo.Bar (c: Real);
     begin
       z := c;
       inherited bar (z)  { or: FooParent.Bar (z) }
     end;

Use FooParent.bar (z) if you want to be sure that this method is called, even if somebody decides not to derive foo directly from fooParent but to have some intermediate object. If you want to call the method bar of the immediate parent - whether it be fooParent or whatever - use inherited bar (z).

To allocate an object on the heap, use New in one of the following manners: 

     var
       MyFoo: FooPtr;
     
       [...]
     
       New (MyFoo, Init (4, 2));
     
       MyFooParent := New (FooPtr, Init (4, 2))

The second possibility has the advantage that MyFoo needn't be a FooPtr but can also be a FooParentPtr, i.e. a pointer to an ancestor of foo.

Destructors can and should be called within Dispose: 

     Dispose (MyFooParent, Fini)

Node: Compiler Directives, Next: , Previous: OOP, Up: Programming

6.9 Compiler Directives And The Preprocessor

GPC, like UCSD Pascal and BP, treats comments beginning with a $ immediately following the opening { or (* as a compiler directive. As in Borland Pascal, {$...} and (*$...*) are equivalent. When a single character plus a + or - follows, this is also called a compiler switch. All of these directives are case-insensitive (but some of them have case-sensitive arguments). Directives are local and can be changed during one compilation (except include files etc. where this makes no sense).

In general, compiler directives are compiler-dependent. (E.g., only the include directive {$I FileName} is common to UCSD and BP.) Because of BP's popularity, GPC supports all of BP's compiler directives (and ignores those that are unnecessary on its platforms - these are those not listed below), but it knows a lot more directives.

Some BP directives are - of course not by chance - just an alternative notation for C preprocessor directives. But there are differences: BP's conditional definitions ({$define Foo}) go into another name space than the program's definitions. Therefore you can define conditionals and check them via {$ifdef Foo}, but the program will not see them as an identifier Foo, so macros do not exist in Borland Pascal.

GPC does support macros, but disables this feature when the --no-macros option or the dialect option --borland-pascal or --delphi is given, to mimic BP's behaviour. Therefore, the following program will react differently when compiled with GPC either without special options or with, e.g., the --borland-pascal option (and in the latter case, it behaves the same as when compiled with BP). 

     program MacroDemo;
     
     const Foo = 'Borland Pascal';
     
     {$define Foo 'Default'}
     
     begin
       WriteLn (Foo)
     end.

Of course, you should not rely on such constructs in your programs. To test if the program is compiled with GPC, you can test the __GPC__ conditional, and to test the dialect used in GPC, you can test the dialect, e.g., with {$ifopt borland-pascal}.

In general, almost every GPC specific command line option (see GPC Command Line Options) can be turned into a compiler directive (exceptions are those options that contain directory names, such as --unit-path, because they refer to the installation on a particular system, and therefore should be set system-wide, rather than in a source file): 

     --foo       {$foo}
     --no-foo    {$no-foo}
     -Wbar       {$W bar}     { note the space after the W }
     -Wno-bar    {$W no-bar}

The following table lists some such examples as well as all those directives that do not correspond to command-line options or have syntactical alternatives (for convenience and/or BP compatibility). 

     --[no-]short-circuit   $B+ $B- like in Borland Pascal:
                                    $B- means short-circuit Boolean
                                    operators; $B+ complete evaluation
     
     --[no-]io-checking     $I+ $I- like in Borland Pascal:
                                    enable/disable I/O checking
     
     --[no-]range-checking  $R+ $R- like in Borland Pascal:
                                    enable/disable range checking
     
     --[no-]stack-checking  $S+ $S- like in Borland Pascal:
                                    enable/disable stack checking
     
     --[no-]typed-address   $T+ $T- like in Borland Pascal:
                                    make the result of the address
                                    operator and the Addr function a
                                    typed or untyped pointer
     
     -W[no-]warnings        $W+ $W- enable/disable warnings. Note: in
                                    --borland-pascal mode, the
                                    short version is disabled because
                                    $W+/$W- has a different meaning in
                                    Borland Pascal (which can safely be
                                    ignored in GPC), but the long version
                                    is still available.
     
     --[no-]extended-syntax $X+ $X- mostly like in Borland Pascal:
                                    enable/disable extended syntax
                                    (ignore function resuls, operator
                                    definitions, PChar, pointer
                                    arithmetic, ...)
     
     --borland-pascal               disable or warn about GPC features
     --extended-pascal              not supported by the standard or
     --pascal-sc                    dialect given, do not warn about its
     etc.                           ``dangerous'' features (especially BP).
                                    The dialect can be changed during one
                                    compilation via directives like,
                                    e.g., {$borland-pascal}.
     
     {$M Hello!}                    write message Hello! to
                                    standard error during compilation. In
                                    --borland-pascal mode, it is
                                    ignored it if only numbers follow
                                    (for compatibility to Borland
                                    Pascal's memory directive)
     
     {$define FOO}                  like in Borland Pascal:
     or                             define FOO (for conditional compilation)
     {$CIDefine FOO}                (case-insensitively)
     
     --cidefine=FOO                 the same on the command line
     
     {$CSDefine FOO}                define FOO case-sensitively
     
     -D FOO                         the same on the command line
     or                             Note: --define on the command
     --csdefine=FOO                 line is case-sensitive like in GCC,
     or                             but {$define} in the source code
     --define=FOO                   is case-insensitive like in BP
     
     {$define loop while True do}   define loop to be while True do
     or                             as a macro like in C. The name of the
     {$CIDefine loop ...}           macro is case-insensitive. Note:
                                    Macros are disabled in
                                    --borland-pascal mode because BP
                                    doesn't support macros.
     
     --cidefine="loop=..."          the same on the command line
     
     {$CSDefine loop ...}           define a case-sensitive macro
     
     --csdefine="loop=..."          the same on the command line
     or
     --define="loop=..."
     
     {$I FileName}                  like in Borland Pascal:
                                    include filename.pas
                                    (the name is converted to lower case)
     
     {$undef FOO}                   like in Borland Pascal: undefine FOO
     
     {$ifdef FOO}                   conditional compilation
       ...                          (like in Borland Pascal).
     {$else}                        Note: GPC predefines the symbol
       ...                          __GPC__ (with two leading
     {$endif}                       and trailing underscores).
     
     {$include "filename.pas"}      include (case-sensitive)
     
     {$include <filename.pas>}      the same, but don't search in the
                                    current directory
...and all the other C preprocessor directives.

You also can use the preprocessor directives in C style, e.g. #include, but this is deprecated because of possible confusion with Borland Pascal style #42 character constants. Besides, in the Pascal style, e.g. {$include "foo.bar"}, there may be more than one directive in the same line.

Node: Library Routines, Next: , Previous: Compiler Directives, Up: Programming

6.10 Routines Built-in or in the Run Time System

In this section we describe the routines and other declarations that are built into the compiler or part of the Run Time System, sorted by topics.

Node: File Routines, Next: , Up: Library Routines

6.10.1 File Routines

Extended Pascal treats files quite differently from Borland Pascal. GPC supports both forms, even in mixed ways, and provides many extensions.

@@ A lot missing here

Note that Prospero's Pascal defaults to creating the file if it does not exists! You need to use Prospero's local addition of setting b.Existing to True to work-around this. GPC does not behave like this.

Node: String Operations, Next: , Previous: File Routines, Up: Library Routines

6.10.2 String Operations

In the following description, s1 and s2 may be arbitrary string expressions, s is a variable of string type.

WriteStr (s, write-parameter-list)

ReadStr (s1, read-parameter-list)
Write to a string and read from a string. The parameter lists are identical to Write/Read from Text files. The semantics is closely modeled after file I/O.
Index (s1, s2)
If s2 is empty, return 1 else if s1 is empty return 0 else returns the position of s2 in s1 (an integer).
Length (s1)
Return the length of s1 (an integer from 0 .. s1.Capacity).
Trim (s1)
Returns a new string with spaces stripped of the end of s.
SubStr (s1, i)

SubStr (s1, i, j)
Return a new substring of s1 that contains j characters starting from i. If j is missing, return all the characters starting from i.
EQ (s1, s2)

NE (s1, s2)

LT (s1, s2)

LE (s1, s2)

GT (s1, s2)

GE (s1, s2)
Lexicographic comparisons of s1 and s2. Returns a boolean result. Strings are not padded with spaces.
s1 = s2

s1 <> s2

s1 < s2

s1 <= s2

s1 > s2

s1 >= s2
Lexicographic comparisons of s1 and s2. Returns a boolean result. The shorter string is blank padded to length of the longer one, but only in --extended-pascal mode.

GPC supports string catenation with the + operator or the Concat function. All string-types are compatible, so you may catenate any chars, fixed length strings and variable length strings. 

     program ConcatDemo (Input, Output);
     
     var
       Ch  : Char;
       Str : String (100);
       Str2: String (50);
       FStr: packed array [1 .. 20] of Char;
     
     begin
        Ch := '$';
        FStr := 'demo';  { padded with blanks }
        Write ('Give me some chars to play with: ');
        ReadLn (Str);
        Str := '^' + 'prefix:' + Str + ':suffix:' + FStr + Ch;
        WriteLn (Concat ('Le', 'ng', 'th'), ' = ', Length (Str));
        WriteLn (Str)
     end.

Note: The length of strings in GPC is limited only by the range of Integer (at least 32 bits, i.e., 2 GB), or the available memory, whichever is smaller. :-)

When trying to write programs portable to other EP compilers, it is however safe to assume a limit of about 32 KB. At least Prospero's Extended Pascal compiler limits strings to 32760 bytes. DEC Pascal limits strings to 65535 bytes.

Node: Accessing Command Line Arguments, Next: , Previous: String Operations, Up: Library Routines

6.10.3 Accessing Command Line Arguments

GPC supports access to the command line arguments with the BP compatible ParamStr and ParamCount functions.

The program below accesses the command line arguments. 

     program CommandLineArgumentsDemo (Output);
     
     var
       Counter: Integer;
     
     begin
       WriteLn ('This program displays command line arguments one per line.');
       for Counter := 0 to ParamCount do
         WriteLn ('Command line argument #', Counter, ' is `',
                  ParamStr (Counter), '''')
     end.

Node: Memory Management Routines, Next: , Previous: Accessing Command Line Arguments, Up: Library Routines

6.10.4 Memory Management Routines

Besides the standard New and Dispose routines, GPC also allows BP style dynamic memory management with GetMem and FreeMem: 

     GetMem (MyPtr, 1024);
     FreeMem (MyPtr, 1024);

One somehow strange feature of Borland is not supported: You cannot free parts of a variable with FreeMem, while the rest is still used and can be freed later by another FreeMem call: 

     program PartialFreeMemDemo;
     
     type
       Vector = array [0 .. 1023] of Integer;
       VecPtr = ^Vector;
     
     var
       p, q: VecPtr;
     
     begin
       GetMem (p, 1024 * SizeOf (Integer));
       q := VecPtr (@p^[512]);
     
       { ... }
     
       FreeMem (p, 512 * SizeOf (Integer));
     
       { ... }
     
       FreeMem (q, 512 * SizeOf (Integer));
     end.

Node: Operations for Integer and Ordinal Types, Next: , Previous: Memory Management Routines, Up: Library Routines

6.10.5 Operations for Integer and Ordinal Types

Node: Complex Number Operations, Next: , Previous: Operations for Integer and Ordinal Types, Up: Library Routines

6.10.6 Complex Number Operations

@@ A lot of details missing here

The following sample programs illustrates most of the Complex type operations. 

     program ComplexOperationsDemo (Output);
     
     var
       z1, z2: Complex;
       Len, Angle: Real;
     
     begin
       z1 := Cmplx (2, 1);
       WriteLn;
       WriteLn ('Complex number z1 is: (', Re (z1) : 1, ',', Im (z1) : 1, ')');
       WriteLn;
       z2 := Conjugate(z1); { GPC extension }
       WriteLn ('Conjugate of z1 is: (', Re (z2) : 1, ',', Im (z2) : 1, ')');
       WriteLn;
       Len   := Abs (z1);
       Angle := Arg (z1);
       WriteLn ('The polar representation of z1 is: Length=', Len : 1,
                ', Angle=', Angle : 1);
       WriteLn;
       z2 := Polar (Len, Angle);
       WriteLn ('Converting (Length, Angle) back to (x, y) gives: (',
                Re (z2) : 1, ',', Im (z2) : 1, ')');
       WriteLn;
       WriteLn ('The following operations operate on the complex number z1');
       WriteLn;
       z2 := ArcTan (z1);
       WriteLn ('ArcTan (z1) = (', Re (z2), ', ', Im (z2), ')');
       WriteLn;
       z2 := z1 ** 3.141;
       WriteLn ('z1 ** 3.141 =', Re (z2), ', ', Im (z2), ')');
       WriteLn;
       z2 := Sin (z1);
       WriteLn ('Sin (z1) = (', Re (z2), ', ', Im (z2), ')');
       WriteLn ('(Cos, Ln, Exp, SqRt and Sqr exist also.)');
       WriteLn;
       z2 := z1 pow 8;
       WriteLn ('z1 pow 8 = (', Re (z2), ', ', Im (z2), ')');
       WriteLn;
       z2 := z1 pow (-8);
       WriteLn ('z1 pow (-8) = (', Re (z2), ', ', Im (z2), ')');
     end.

Node: Set Operations, Next: , Previous: Complex Number Operations, Up: Library Routines

6.10.7 Set Operations

GPC supports Standard Pascal set operations. In addition it supports the Extended Pascal set operation symmetric difference (set1 >< set2) operation whose result consists of those elements which are in exactly one of the operannds.

It also has a function that counts the elements in the set: a := Card (set1).

In the following description, S1 and S2 are variables of set type, s is of the base type of the set.

S1 := S2
Assign a set to a set variable.
S1 + S2
Union of sets.
S1 - S2
Difference between two sets.
S1 * S2
Intersection of two sets.
S1 >< S2
Symmetric difference
S1 = S2
Comparison between two sets. Returns boolean result. True if S1 has the same elements as S2.
S1 <> S2
Comparison between two sets. Returns boolean result. True if S1 does not have the same elements as S2.
S1 < S2

S2 > S1
Comparison between two sets. Returns boolean result. True if S1 is a strict subset of S2.
S1 <= S2

S2 >= S1
Comparison between two sets. Returns boolean result. True if S1 is a subset of (or equal to) S2.
s in S1
Set membership test between an element s and a set. Returns boolean result. True if s is an element of S1.

The following example demonstrates some set operations. The results of the operations are given in the comments. 

     program SetOpDemo;
     
     type
       TCharSet = set of Char;
     
     var
       S1, S2, S3: TCharSet;
       Result: Boolean;
     
     begin
       S1 := ['a', 'b', 'c'];
       S2 := ['c', 'd', 'e'];
       S3 := S1 + S2;       { S3 = ['a', 'b', 'c', 'd', 'e'] }
       S3 := S1 * S2;       { S3 = ['c'] }
       S3 := S1 - S2;       { S3 = ['a', 'b'] }
       S3 := S1 >< S2;      { S3 = ['a', 'b', 'd', 'e'] }
     
       S1 := ['c', 'd', 'e'];
       Result := S1 = S2;   { False }
       Result := S1 < S2;   { False }
       Result := S1 <= S2;  { True }
     
       S1 := ['c', 'd'];
       Result := S1 <> S2;  { True }
       Result := S2 > S1;   { True }
       Result := S2 >= S1   { True }
     end.

Node: Date And Time Routines, Previous: Set Operations, Up: Library Routines

6.10.8 Date And Time Routines

procedure GetTimeStamp (var t: TimeStamp);

function Date (t: TimeStamp): packed array [1 .. DateLength] of Char;

function Time (t: TimeStamp): packed array [1 .. TimeLength] of Char;

DateLength and TimeLength are implementation dependent constants.

GetTimeStamp (t) fills the record t with values. If they are valid, the Boolean flags are set to True.

TimeStamp is a predefined type in the Extended Pascal standard. It may be extended in an implementation, and is indeed extended in GPC. For the full definition of TimeStamp, see TimeStamp.

Node: Other Languages, Next: , Previous: Library Routines, Up: Programming

6.11 Interfacing with Other Languages

The standardized GNU compiler back-end makes it relatively easy to share libraries between GNU Pascal and other GNU compilers. On Unix-like platforms (not on Dos-like platforms), the GNU compiler back-end usually complies to the standards defined for that system, so communication with other compilers should be easy, too.

In this chapter we discuss how to import libraries written in other languages, and how to import libraries written in GNU Pascal from other languages. While the examples will specialize to compatibility to GNU C, generalization is straightforward if you are familiar with the other language in question.

Node: Importing Libraries from Other Languages, Next: , Up: Other Languages

6.11.1 Importing Libraries from Other Languages

To use a function written in another language, you need to provide an external declaration for it - either in the program, or in the interface part of a unit, or a module.

Let's say you want to use the following C library from Pascal: 

     File `callc.c':
     
     #include <unistd.h>
     #include "callc.h"
     
     int foo = 1;
     
     void bar (void)
     {
       sleep (foo);
     }
     
     File `callc.h':
     
     /* Actually, we wouldn't need this header file, and could instead
        put these prototypes into callc.c, unless we want to use callc.c
        also from other C source files. */
     
     extern int foo;
     extern void bar (void);

Then your program can look like this: 

     program CallCDemo;
     
     {$L callc.c}  { Or: `callc.o' if you don't have the source }
     
     var
       MyFoo: Integer; external name 'foo';
     
     procedure Bar; external name 'bar';
     
     begin
       MyFoo := 42;
       Bar
     end.

Or, if you want to provide a CallCUnit unit: 

     unit CallCUnit;
     
     interface
     
     var
       MyFoo: Integer; external name 'foo';
     
     procedure Bar; external name 'bar';
     
     implementation
     
     {$L callc.c}  { Or: `callc.o' if you don't have the source }
     
     end.
     
     program CallCUDemo;
     
     uses CallCUnit;
     
     begin
       MyFoo := 42;
       Bar
     end.

You can either link your program manually with callc.o or put a compiler directive {$L callc.o} into your program or unit, and then GPC takes care of correct linking. If you have the source of the C library (you always have it if it is Free Software), you can even write {$L callc.c} in the program (like above). Then GPC will also link with callc.o, but in addition GPC will run the C compiler whenever callc.c has changed if --automake is given, too.

While it is often convenient, there is no must to give the C function bar the name Bar in Pascal; you can name it as you like (e.g., the variable MyFoo has a C name of foo in the example above).

If you omit the name, the default is the Pascal identifier, converted to lower-case. So, in this example, the name could be omitted for Bar, but not for MyFoo.

It is important that data types of both languages are mapped correctly onto each other. C's int, for instance, translates to GPC's Integer, and C's unsigned long to MedCard. For a complete list of integer types with their C counterparts, see Integer Types.

In some cases it can be reasonable to translate a C pointer parameter to a Pascal var parameter. Since const parameters in GPC can be passed by value or by reference internally, possibly depending on the system, const foo * parameters to C functions cannot reliably be declared as const in Pascal. However, Extended Pascal's protected var can be used since this guarantees passing by reference.

Some libraries provide a main function and require your program's "main" to be named differently. To achive this with GPC, invoke it with an option --gpc-main="GPCmain" (where GPCmain is an example how you might want to name the program). You can also write it into your source as a directive {$gpc-main="GPCmain"}.

Node: Exporting GPC Libraries to Other Languages, Previous: Importing Libraries from Other Languages, Up: Other Languages

6.11.2 Exporting GPC Libraries to Other Languages

The .o files produced by GPC are in the same format as those of all other GNU compilers, so there is no problem in writing libraries for other languages in Pascal. To use them, you will need to write kind of interface - a header file in C. However there are some things to take into account, especially if your Pascal unit exports objects:

Node: Notes for Debugging, Next: , Previous: Other Languages, Up: Programming

6.12 Notes for Debugging

Node: I18N, Next: , Previous: Notes for Debugging, Up: Programming

6.13 How to use I18N in own programs

This chapter discusses shortly how to use the Internationalization (I18N) features of GNU Pascal.

Prerequisite

You need to have gettext installed. Try to compile demos/gettextdemo.pas. Furthermore, you should download a tool named pas2po from http://www.gnu-pascal.org/contrib/eike/.

The source

We would like to translate the messages provided with this simple example different languages (here: German) without touching the source for each language: 

     program Hello1;
     
     begin
       WriteLn ('Hello, World!');
       WriteLn ('The answer of the questions is: ', 42)
     end.

Preparing the source

To do so, we must prepare the source to use gettext: 

     program Hello2;
     
     uses GPC, Intl;
     
     var Dummy, s: TString;
     
     begin
       Dummy := BindTextDomain ('hello2', '/usr/share/locale/');
       Dummy := TextDomain ('hello2');
       WriteLn (GetText ('Hello, World!'));
       s := FormatString (GetText ('The answer of the questions is %s'), 42);
       WriteLn (s)
     end.

BindTextDomain sets the path to find our message catalogs in the system. This path is system dependent. TextDomain tells the program to use this catalog. GetText looks up the given string in the catalog and returns a translated string within the current locale settings. FormatString replaces some format specifiers with the following argument. %s is the first following argument. After this step is done, we do not need to touch the sourcefile any longer. The output of this program is as follows: 

     Hello, World!
     The answer of the questions is 42

Getting the translatable strings

There are lots of strings in the above example, but only those surrounded with GetText should be translated. We use pas2po hello2.pas -o hello2.po to extract the messages. The output is: 

     # This file was created by pas2po with 'hello2.pas'.
     # Please change this file manually.
     # SOME DESCRIPTIVE TITLE.
     # Copyright (C) YEAR Free Software Foundation, Inc.
     # FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
     #
     #, fuzzy
     msgid ""
     msgstr ""
     "Project-Id-Version: PACKAGE VERSION\n"
     "POT-Creation-Date: 2003-04-27 20:48+0200\n"
     "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
     "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
     "Language-Team: LANGUAGE <LL@li.org>\n"
     "MIME-Version: 1.0\n"
     "Content-Type: text/plain; charset=CHARSET\n"
     "Content-Transfer-Encoding: 8bit\n"
     
     #hello2.pas:10
     msgid "Hello, World!"
     msgstr ""
     
     #hello2.pas:11
     msgid "The answer of the questions is %s"
     msgstr ""

Now we translate the message ids into German language, and set some needful informations at their appropriate places. The following steps must be repeated for each language we would like to support: 

     # This file was created by pas2po with 'hello2.pas'.
     # Copyright (C) 2003 Free Software Foundation, Inc.
     # Eike Lange  <eike@g-n-u.de>, 2003.
     msgid ""
     msgstr ""
     "Project-Id-Version: Hello2 1.0\n"
     "POT-Creation-Date: 2003-04-27 12:00+0200\n"
     "PO-Revision-Date: 2003-04-27 12:06+0200\n"
     "Last-Translator: Eike Lange <eike@g-n-u.de>\n"
     "Language-Team: de <de@li.org>\n"
     "MIME-Version: 1.0\n"
     "Content-Type: text/plain; charset=ISO-8859-1\n"
     "Content-Transfer-Encoding: 8bit\n"
     
     #hello2.pas:10
     msgid "Hello, World!"
     msgstr "Hallo, Welt!"
     
     #hello2.pas:11
     msgid "The answer of the questions is %s"
     msgstr "'%s' lautet die Antwort auf die Frage."

Please note that we swapped text and numeric arguments and added some single quotes arround the first argument. We compile the message catalog with msgfmt -vv hello2.po -o hello2.mo and install the file hello2.mo at /usr/share/locale/de/LC_MESSAGES/ With a german locale setting, the output should be as follows: 

     Hallo, Welt!
     '42' lautet die Antwort auf die Frage.

System dependent notes:

The topmost path where message catalogs reside is system dependent:

for DJGPP:
GetEnv ('$DJDIR') + '/share/locale'
for Mac OS X:
/usr/share/locale or /sw/share/locale
for Linux, *BSD:
/usr/share/locale or /usr/local/share/locale

See also

Gettext, FormatString, Intl.

Node: Run Time System, Next: , Previous: I18N, Up: Programming

6.14 Pascal declarations for GPC's Run Time System

Below is a Pascal source of the declarations in GPC's Run Time System (RTS). A file gpc.pas with the same contents is included in the GPC distribution in a units subdirectory of the directory containing libgcc.a. (To find out the correct directory for your installation, type gpc --print-file-name=units on the command line.) 

     { This file was generated automatically from gpc-pas.in.
       DO NOT CHANGE THIS FILE MANUALLY! }
     
     { Pascal declarations of the GPC Run Time System that are visible to
       each program.
     
       This unit contains Pascal declarations of many RTS routines which
       are not built into the compiler and can be called from programs.
       Don't copy the declarations from this unit into your programs, but
       rather include this unit with a uses statement. The reason is
       that the internal declarations, e.g. the linker names, may change,
       and this unit will be changed accordingly. @@In the future, this
       unit might be included into every program automatically, so there
       will be no need for a uses statement to make the declarations
       here available.
     
       Note about protected var parameters:
       Since const parameters in GPC may be passed by value *or* by
       reference internally, possibly depending on the system,
       const foo* parameters to C functions *cannot* reliably be
       declared as const in Pascal. However, Extended Pascal's
       protected var can be used since this guarantees passing by
       reference.
     
       Copyright (C) 1998-2004 Free Software Foundation, Inc.
     
       Authors: Jukka Virtanen <jtv@hut.fi>
                Peter Gerwinski <peter@gerwinski.de>
                Frank Heckenbach <frank@pascal.gnu.de>
                J.J. v.der Heijden <j.j.vanderheijden@student.utwente.nl>
                Nicola Girardi <nicola@g-n-u.de>
                Prof. Abimbola A. Olowofoyeku <African_Chief@bigfoot.com>
                Emil Jerabek <jerabek@math.cas.cz>
                Maurice Lombardi <Maurice.Lombardi@ujf-grenoble.fr>
                Toby Ewing <ewing@iastate.edu>
                Mirsad Todorovac <mtodorov_69@yahoo.com>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ <> 20040516}
     {$error
     Trying to compile gpc.pas with a non-matching GPC version is likely
     to cause problems.
     
     In case you are building the RTS separately from GPC, make sure you
     install a current GPC version previously. If you are building GPC
     now and this message appears, something is wrong -- if you are
     overriding the GCC_FOR_TARGET or GPC_FOR_TARGET make variables, this
     might be the problem. If you are cross-building GPC, build and
     install a current GPC cross-compiler first, sorry. If that's not the
     case, please report it as a bug.
     
     If you are not building GPC or the RTS currently, you might have
     installed things in the wrong place, so the compiler and RTS
     versions do not match.}
     {$endif}
     
     { Command-line options must not change the layout of RTS types
       declared here. }
     {$no-pack-struct, maximum-field-alignment 0}
     
     module GPC;
     
     export
       GPC = all;
       GPC_CP = (ERead { @@ not really, but an empty export doesn't work
       } );
       GPC_EP = (ERead { @@ not really, but an empty export doesn't work
       } );
       GPC_BP = (MaxLongInt, ExitCode, ErrorAddr, FileMode, Pos);
       GPC_Delphi = (MaxLongInt, Int64, InitProc, EConvertError,
                     ExitCode, ErrorAddr, FileMode, Pos, SetString,
       StringOfChar,
                     TextFile, AssignFile, CloseFile);
     
     { Pascal declarations of the GPC Run Time System routines that are
       implemented in C, from rtsc.pas }
     
     const
       MaxLongInt = High (LongInt);
     
       { Maximum size of a variable }
       MaxVarSize = MaxInt div 8;
     
     { If set, characters >= #$80 are assumed to be letters even if the
       locale routines don't say so. This is a kludge because some
       systems don't have correct non-English locale tables. }
     var
       FakeHighLetters: Boolean; attribute (name = '_p_FakeHighLetters');
       external;
     
     type
       PCStrings = ^TCStrings;
       TCStrings = array [0 .. MaxVarSize div SizeOf (CString) - 1] of
       CString;
     
       Int64 = Integer attribute (Size = 64);
       UnixTimeType = LongInt;  { This is hard-coded in the compiler. Do
       not change here. }
       MicroSecondTimeType = LongInt;
       FileSizeType = LongInt;
       SignedSizeType = Integer attribute (Size = BitSizeOf (SizeType));
       TSignalHandler = procedure (Signal: Integer);
     
       StatFSBuffer = record
         BlockSize, BlocksTotal, BlocksFree: LongestInt;
         FilesTotal, FilesFree: Integer
       end;
     
       InternalSelectType = record
         Handle: Integer;
         Read, Write, Exception: Boolean
       end;
     
       PString = ^String;
     
       { Max so the range of the array does not become invalid for
         Count = 0 }
       PPStrings = ^TPStrings;
       TPStrings (Count: Cardinal) = array [1 .. Max (Count, 1)] of
       PString;
     
       GlobBuffer = record
         Result: PPStrings;
         Internal1: Pointer;
         Internal2: PCStrings;
         Internal3: Integer
       end;
     
     { Mathematical routines }
     
     function  SinH (x: Real): Real; attribute (const); external
       name '_p_SinH';
     function  CosH (x: Real): Real; attribute (const); external
       name '_p_CosH';
     function  ArcTan2 (y: Real; x: Real): Real; attribute (const);
       external name '_p_ArcTan2';
     function  IsInfinity (x: LongReal): Boolean; attribute (const);
       external name '_p_IsInfinity';
     function  IsNotANumber (x: LongReal): Boolean; attribute (const);
       external name '_p_IsNotANumber';
     procedure SplitReal (x: LongReal; var Exponent: Integer; var
       Mantissa: LongReal); external name '_p_SplitReal';
     
     { Character routines }
     
     { Convert a character to upper case, according to the current
       locale.
       Except in --borland-pascal mode, UpCase does the same. }
     function  UpCase (ch: Char): Char; attribute (const); external
       name '_p_UpCase';
     
     { Convert a character to lower case, according to the current
       locale. }
     function  LoCase (ch: Char): Char; attribute (const); external
       name '_p_LoCase';
     function  IsUpCase (ch: Char): Boolean; attribute (const); external
       name '_p_IsUpCase';
     function  IsLoCase (ch: Char): Boolean; attribute (const); external
       name '_p_IsLoCase';
     function  IsAlpha (ch: Char): Boolean; attribute (const); external
       name '_p_IsAlpha';
     function  IsAlphaNum (ch: Char): Boolean; attribute (const);
       external name '_p_IsAlphaNum';
     function  IsAlphaNumUnderscore (ch: Char): Boolean; attribute
       (const); external name '_p_IsAlphaNumUnderscore';
     function  IsSpace (ch: Char): Boolean; attribute (const); external
       name '_p_IsSpace';
     function  IsPrintable (ch: Char): Boolean; attribute (const);
       external name '_p_IsPrintable';
     
     { Time routines }
     
     { Sleep for a given number of seconds. }
     procedure Sleep (Seconds: Integer); external name '_p_Sleep';
     
     { Sleep for a given number of microseconds. }
     procedure SleepMicroSeconds (MicroSeconds: Integer); external
       name '_p_SleepMicroSeconds';
     
     { Set an alarm timer. }
     function  Alarm (Seconds: Integer): Integer; external
       name '_p_Alarm';
     
     { Convert a Unix time value to broken-down local time.
       All parameters except Time may be Null. }
     procedure UnixTimeToTime (Time: UnixTimeType; var Year: Integer; var
       Month: Integer; var Day: Integer; var Hour: Integer; var Minute:
       Integer; var Second: Integer;
                                     var TimeZone: Integer; var DST:
       Boolean; var TZName1: CString; var TZName2: CString); external
       name '_p_UnixTimeToTime';
     
     { Convert broken-down local time to a Unix time value. }
     function  TimeToUnixTime (Year: Integer; Month: Integer; Day:
       Integer; Hour: Integer; Minute: Integer; Second: Integer):
       UnixTimeType; external name '_p_TimeToUnixTime';
     
     { Get the real time. MicroSecond can be Null and is ignored then. }
     function  GetUnixTime (var MicroSecond: Integer): UnixTimeType;
       external name '_p_GetUnixTime';
     
     { Get the CPU time used. MicroSecond can be Null and is ignored
       then. Now, GetCPUTime can measure long CPU times reliably on most
       systems (e.g. Solaris where it didn't work before). }
     function  GetCPUTime (var MicroSecond: Integer): Integer; external
       name '_p_GetCPUTime';
     
     { Signal and process routines }
     
     { Extract information from the status returned by PWait }
     function  StatusExited (Status: Integer): Boolean; attribute
       (const); external name '_p_StatusExited';
     function  StatusExitCode (Status: Integer): Integer; attribute
       (const); external name '_p_StatusExitCode';
     function  StatusSignaled (Status: Integer): Boolean; attribute
       (const); external name '_p_StatusSignaled';
     function  StatusTermSignal (Status: Integer): Integer; attribute
       (const); external name '_p_StatusTermSignal';
     function  StatusStopped (Status: Integer): Boolean; attribute
       (const); external name '_p_StatusStopped';
     function  StatusStopSignal (Status: Integer): Integer; attribute
       (const); external name '_p_StatusStopSignal';
     
     { Install a signal handler and optionally return the previous
       handler. OldHandler and OldRestart may be Null. }
     function  InstallSignalHandler (Signal: Integer; Handler:
       TSignalHandler; Restart: Boolean; UnlessIgnored: Boolean;
       var OldHandler: TSignalHandler; var OldRestart: Boolean): Boolean;
       external name '_p_InstallSignalHandler';
     
     { Block or unblock a signal. }
     procedure BlockSignal (Signal: Integer; Block: Boolean); external
       name '_p_BlockSignal';
     
     { Test whether a signal is blocked. }
     function  SignalBlocked (Signal: Integer): Boolean; external
       name '_p_SignalBlocked';
     
     { Sends a signal to a process. Returns True if successful. If Signal
       is 0, it doesn't send a signal, but still checks whether it would
       be possible to send a signal to the given process. }
     function  Kill (PID: Integer; Signal: Integer): Boolean; external
       name '_p_Kill';
     
     { Constant for WaitPID }
     const
       AnyChild = -1;
     
     { Waits for a child process with the given PID (or any child process
       if PID = AnyChild) to terminate or be stopped. Returns the PID of
       the process. WStatus will contain the status and can be evaluated
       with StatusExited etc.. If nothing happened, and Block is False,
       the function will return 0, and WStatus will be 0. If an error
       occurred (especially on single tasking systems where WaitPID is
       not possible), the function will return a negative value, and
       WStatus will be 0. }
     function  WaitPID (PID: Integer; var WStatus: Integer; Block:
       Boolean): Integer; external name '_p_WaitPID';
     
     { Returns the process ID. }
     function  ProcessID: Integer; external name '_p_ProcessID';
     
     { Returns the process group. }
     function  ProcessGroup: Integer; external name '_p_ProcessGroup';
     
     { Returns the real or effective user ID of the process. }
     function  UserID (Effective: Boolean): Integer; external
       name '_p_UserID';
     
     { Tries to change the real and/or effective user ID. }
     function  SetUserID (Real: Integer; Effective: Integer): Boolean;
       external name '_p_SetUserID';
     
     { Returns the real or effective group ID of the process. }
     function  GroupID (Effective: Boolean): Integer; external
       name '_p_GroupID';
     
     { Tries to change the real and/or effective group ID. }
     function  SetGroupID (Real: Integer; Effective: Integer): Boolean;
       external name '_p_SetGroupID';
     
     { Low-level file routines. Mostly for internal use. }
     
     { Get information about a file system. }
     function  StatFS (Path: CString; var Buf: StatFSBuffer): Boolean;
       external name '_p_StatFS';
     function  CStringOpenDir (DirName: CString): Pointer; external
       name '_p_CStringOpenDir';
     function  CStringReadDir (Dir: Pointer): CString; external
       name '_p_CStringReadDir';
     procedure CStringCloseDir (Dir: Pointer); external
       name '_p_CStringCloseDir';
     
     { Returns the value of the symlink FileName in a CString allocated
       from the heap. Returns nil if it is no symlink or the function
       is not supported. }
     function  ReadLink (FileName: CString): CString; external
       name '_p_ReadLink';
     
     { The result of the following function is a pointer to a *static*
       buffer! }
     function  CStringRealPath (Path: CString): CString; external
       name '_p_CStringRealPath';
     
     { File mode constants that are ORed for BindingType.Mode, ChMod,
       CStringChMod and Stat. The values below are valid for all OSs
       (as far as supported). If the OS uses different values, they're
       converted internally. }
     const
       fm_SetUID           = 8#4000;
       fm_SetGID           = 8#2000;
       fm_Sticky           = 8#1000;
       fm_UserReadable     = 8#400;
       fm_UserWritable     = 8#200;
       fm_UserExecutable   = 8#100;
       fm_GroupReadable    = 8#40;
       fm_GroupWritable    = 8#20;
       fm_GroupExecutable  = 8#10;
       fm_OthersReadable   = 8#4;
       fm_OthersWritable   = 8#2;
       fm_OthersExecutable = 8#1;
     
     { Constants for Access and OpenHandle }
     const
       MODE_EXEC     = 1 shl 0;
       MODE_WRITE    = 1 shl 1;
       MODE_READ     = 1 shl 2;
       MODE_FILE     = 1 shl 3;
       MODE_DIR      = 1 shl 4;
       MODE_SPECIAL  = 1 shl 5;
       MODE_SYMLINK  = 1 shl 6;
       MODE_CREATE   = 1 shl 7;
       MODE_EXCL     = 1 shl 8;
       MODE_TRUNCATE = 1 shl 9;
       MODE_BINARY   = 1 shl 10;
     
     { Check if a file name is accessible. }
     function  Access (FileName: CString; Request: Integer): Integer;
       external name '_p_Access';
     
     { Get information about a file. Any argument except FileName can
       be Null. }
     function  Stat (FileName: CString; var Size: FileSizeType;
       var ATime: UnixTimeType; var MTime: UnixTimeType; var CTime:
       UnixTimeType;
       var User: Integer; var Group: Integer; var Mode: Integer; var
       Device: Integer; var INode: Integer; var Links: Integer;
       var SymLink: Boolean; var Dir: Boolean; var Special: Boolean):
       Integer; external name '_p_Stat';
     function  OpenHandle (FileName: CString; Mode: Integer): Integer;
       external name '_p_OpenHandle';
     function  ReadHandle (Handle: Integer; Buffer: Pointer; Size:
       SizeType): SignedSizeType; external name '_p_ReadHandle';
     function  WriteHandle (Handle: Integer; Buffer: Pointer; Size:
       SizeType): SignedSizeType; external name '_p_WriteHandle';
     function  CloseHandle (Handle: Integer): Integer; external
       name '_p_CloseHandle';
     procedure FlushHandle (Handle: Integer); external
       name '_p_FlushHandle';
     function  DupHandle (Src: Integer; Dest: Integer): Integer; external
       name '_p_DupHandle';
     function  CStringRename (OldName: CString; NewName: CString):
       Integer; external name '_p_CStringRename';
     function  CStringUnlink (FileName: CString): Integer; external
       name '_p_CStringUnlink';
     function  CStringChDir (FileName: CString): Integer; external
       name '_p_CStringChDir';
     function  CStringMkDir (FileName: CString): Integer; external
       name '_p_CStringMkDir';
     function  CStringRmDir (FileName: CString): Integer; external
       name '_p_CStringRmDir';
     function  UMask (Mask: Integer): Integer; attribute (ignorable);
       external name '_p_UMask';
     function  CStringChMod (FileName: CString; Mode: Integer): Integer;
       external name '_p_CStringChMod';
     function  CStringChOwn (FileName: CString; Owner: Integer; Group:
       Integer): Integer; external name '_p_CStringChOwn';
     function  CStringUTime (FileName: CString; AccessTime: UnixTimeType;
       ModificationTime: UnixTimeType): Integer; external
       name '_p_CStringUTime';
     
     { Constants for SeekHandle }
     const
       SeekAbsolute = 0;
       SeekRelative = 1;
       SeekFileEnd  = 2;
     
     { Seek to a position on a file handle. }
     function  SeekHandle (Handle: Integer; Offset: FileSizeType; Whence:
       Integer): FileSizeType; external name '_p_SeekHandle';
     
     function  TruncateHandle (Handle: Integer; Size: FileSizeType):
       Integer; external name '_p_TruncateHandle';
     function  LockHandle (Handle: Integer; WriteLock: Boolean; Block:
       Boolean): Boolean; external name '_p_LockHandle';
     function  UnlockHandle (Handle: Integer): Boolean; external
       name '_p_UnlockHandle';
     function  SelectHandle (Count: Integer; var Events:
       InternalSelectType; MicroSeconds: MicroSecondTimeType): Integer;
       external name '_p_SelectHandle';
     
     { Constants for MMapHandle and MemoryMap }
     const
       mm_Readable   = 1;
       mm_Writable   = 2;
       mm_Executable = 4;
     
     { Try to map (a part of) a file to memory. }
     function  MMapHandle (Start: Pointer; Length: SizeType; Access:
       Integer; Shared: Boolean; Handle: Integer; Offset: FileSizeType):
       Pointer; external name '_p_MMapHandle';
     
     { Unmap a previous memory mapping. }
     function  MUnMapHandle (Start: Pointer; Length: SizeType): Integer;
       external name '_p_MUnMapHandle';
     
     { Returns the file name of the terminal device that is open on
       Handle. Returns nil if (and only if) Handle is not open or not
       connected to a terminal. If NeedName is False, it doesn't bother
       to search for the real name and just returns DefaultName if it
       is a terminal and nil otherwise. DefaultName is also returned if
       NeedName is True, Handle is connected to a terminal, but the
       system does not provide information about the real file name. }
     function  GetTerminalNameHandle (Handle: Integer; NeedName: Boolean;
       DefaultName: CString): CString; external
       name '_p_GetTerminalNameHandle';
     
     { I/O routines }
     
     { Sets the process group of Process (or the current one if Process
       is 0) to ProcessGroup (or its PID if ProcessGroup is 0). Returns
       True if successful. }
     function  SetProcessGroup (Process: Integer; ProcessGroup: Integer):
       Boolean; external name '_p_SetProcessGroup';
     
     { Sets the process group of a terminal given by Terminal (as a file
       handle) to ProcessGroup. ProcessGroup must be the ID of a process
       group in the same session. Returns True if successful. }
     function  SetTerminalProcessGroup (Handle: Integer; ProcessGroup:
       Integer): Boolean; external name '_p_SetTerminalProcessGroup';
     
     { Returns the process group of a terminal given by Terminal (as a
       file handle), or -1 on error. }
     function  GetTerminalProcessGroup (Handle: Integer): Integer;
       external name '_p_GetTerminalProcessGroup';
     
     { Set the standard input's signal generation, if it is a terminal. }
     procedure SetInputSignals (Signals: Boolean); external
       name '_p_SetInputSignals';
     
     { Get the standard input's signal generation, if it is a terminal. }
     function  GetInputSignals: Boolean; external
       name '_p_GetInputSignals';
     
     { Internal routines }
     
     { Returns system information if available. Fields not available will
       be set to nil. }
     procedure CStringSystemInfo (var SysName: CString; var NodeName:
       CString; var Release: CString; var Version: CString; var Machine:
       CString; var DomainName: CString); external
       name '_p_CStringSystemInfo';
     
     { Returns the path of the running executable *if possible*. }
     function  CStringExecutablePath (Buffer: CString): CString; external
       name '_p_CStringExecutablePath';
     
     { Sets ErrNo to the value of errno and returns the description
       for this error. May return nil if not supported! ErrNo may be
       Null (then only the description is returned). }
     function  CStringStrError (var ErrNo: Integer): CString; external
       name '_p_CStringStrError';
     
     { File routines }
     
     type
       TOpenMode = (fo_None, fo_Reset, fo_Rewrite, fo_Append,
       fo_SeekRead, fo_SeekWrite, fo_SeekUpdate);
       PAnyFile = ^AnyFile;
     
     var
       FileMode: Integer; external name '_p_FileMode'; external;
     
     procedure GetBinding   (protected var aFile: AnyFile; var aBinding:
       BindingType); external name '_p_GetBinding';
     procedure ClearBinding (var aBinding: BindingType); external
       name '_p_ClearBinding';
     
     { TFDD interface @@ Subject to change! Use with caution! }
     
     type
       TOpenProc   = procedure (var PrivateData; Mode: TOpenMode);
       TSelectFunc = function  (var PrivateData; Writing: Boolean):
       Integer;  { called before SelectHandle, must return a file handle
       }
       TSelectProc = procedure (var PrivateData; var ReadSelect,
       WriteSelect, ExceptSelect: Boolean);  { called before and after
       SelectHandle }
       TReadFunc   = function  (var PrivateData; var   Buffer; Size:
       SizeType): SizeType;
       TWriteFunc  = function  (var PrivateData; const Buffer; Size:
       SizeType): SizeType;
       TFileProc   = procedure (var PrivateData);
       TFlushProc  = TFileProc;
       TCloseProc  = TFileProc;
       TDoneProc   = TFileProc;
     
     procedure AssignTFDD (var f: AnyFile;
                           OpenProc   : TOpenProc;
                           SelectFunc : TSelectFunc;
                           SelectProc : TSelectProc;
                           ReadFunc   : TReadFunc;
                           WriteFunc  : TWriteFunc;
                           FlushProc  : TFlushProc;
                           CloseProc  : TCloseProc;
                           DoneProc   : TDoneProc;
                           PrivateData: Pointer); external
       name '_p_AssignTFDD';
     
     procedure SetTFDD    (var f: AnyFile;
                           OpenProc   : TOpenProc;
                           SelectFunc : TSelectFunc;
                           SelectProc : TSelectProc;
                           ReadFunc   : TReadFunc;
                           WriteFunc  : TWriteFunc;
                           FlushProc  : TFlushProc;
                           CloseProc  : TCloseProc;
                           DoneProc   : TDoneProc;
                           PrivateData: Pointer); external
       name '_p_SetTFDD';
     
     { Any parameter except f may be Null }
     procedure GetTFDD    (var f: AnyFile;
                           var OpenProc   : TOpenProc;
                           var SelectFunc : TSelectFunc;
                           var SelectProc : TSelectProc;
                           var ReadFunc   : TReadFunc;
                           var WriteFunc  : TWriteFunc;
                           var FlushProc  : TFlushProc;
                           var CloseProc  : TCloseProc;
                           var DoneProc   : TDoneProc;
                           var PrivateData: Pointer); external
       name '_p_GetTFDD';
     
     procedure FileMove (var f: AnyFile; NewName: CString; Overwrite:
       Boolean); attribute (iocritical); external name '_p_Mv';
     
     { Flags that can be ORed into FileMode. The default value of
       FileMode is FileMode_Reset_ReadWrite. The somewhat confusing
       values are meant to be compatible to BP (as far as BP supports
       them). }
     const
       { Allow writing to binary files opened with Reset }
       FileMode_Reset_ReadWrite      = 2;
     
       { Do not allow reading from files opened with Rewrite }
       FileMode_Rewrite_WriteOnly    = 4;
     
       { Do not allow reading from files opened with Extend }
       FileMode_Extend_WriteOnly     = 8;
     
       { Allow writing to text files opened with Reset }
       FileMode_Text_Reset_ReadWrite = $100;
     
     type
       TextFile = Text;
     
     const
       NoChange = -1;  { can be passed to ChOwn for Owner and/or Group to
       not change that value }
     
     procedure CloseFile (var aFile: AnyFile); external
       name '_p_CloseFile';
     procedure ChMod (var aFile: AnyFile; Mode: Integer); attribute
       (iocritical); external name '_p_ChMod';
     procedure ChOwn (var aFile: AnyFile; Owner, Group: Integer);
       attribute (iocritical); external name '_p_ChOwn';
     
     { Checks if data are available to be read from aFile. This is
       similar to not EOF (aFile), but does not block on "files" that
       can grow, like Ttys or pipes. }
     function  CanRead      (var aFile: AnyFile): Boolean; external
       name '_p_CanRead';
     
     { Checks if data can be written to aFile. }
     function  CanWrite     (var aFile: AnyFile): Boolean; external
       name '_p_CanWrite';
     
     { Get the file handle. }
     function  FileHandle   (protected var aFile: AnyFile): Integer;
       external name '_p_FileHandle';
     
     { Lock files }
     function  FileLock   (var aFile: AnyFile; WriteLock, Block:
       Boolean): Boolean; external name '_p_FileLock';
     function  FileUnlock (var aFile: AnyFile): Boolean; external
       name '_p_FileUnlock';
     
     { Try to map (a part of) a file to memory. }
     function  MemoryMap (Start: Pointer; Length: SizeType; Access:
       Integer; Shared: Boolean;
                          var aFile: AnyFile; Offset: FileSizeType):
       Pointer; external name '_p_MemoryMap';
     
     { Unmap a previous memory mapping. }
     procedure MemoryUnMap (Start: Pointer; Length: SizeType); external
       name '_p_MemoryUnMap';
     
     procedure RTSInitFile; external name '_p_init_GPC_File';
     
     { Mathematical routines, from math.pas }
     
     function Ln1Plus  (x: Real): Real; attribute (const, name
       = '_p_Ln1Plus'); external;
     
     { String handling routines (lower level), from string1.pas }
     
     { TString is a string type that is used for function results and
       local variables, as long as undiscriminated strings are not
       allowed there. The default size of 2048 characters should be
       enough for file names on any system, but can be changed when
       necessary. It should be at least as big as MAXPATHLEN. }
     
     const
       TStringSize = 2048;
       SpaceCharacters = [' ', #9];
       NewLine = "\n";  { the separator of lines within a string }
       LineBreak = {$if defined (__OS_DOS__) and not defined (__CYGWIN__)
       and not defined (__MSYS__)}
                   "\r\n"
                   {$else}
                   "\n"
                   {$endif};  { the separator of lines within a file }
     
     type
       TString    = String (TStringSize);
       TStringBuf = packed array [0 .. TStringSize] of Char;
       CharSet    = set of Char;
       Str64      = String (64);
       TInteger2StringBase = 2 .. 36;
       TInteger2StringWidth = 0 .. High (TString);
     
     var
       NumericBaseDigits: array [0 .. 35] of Char; attribute (const, name
       = '_p_NumericBaseDigits'); external;
       NumericBaseDigitsUpper: array [0 .. 35] of Char; attribute (const,
       name = '_p_NumericBaseDigitsUpper'); external;
     
       CParamCount: Integer; attribute (name = '_p_CParamCount');
       external;
       CParameters: PCStrings; attribute (name = '_p_CParameters');
       external;
     
     function  MemCmp      (const s1, s2; Size: SizeType): Integer;
       external name 'memcmp';
     function  MemComp     (const s1, s2; Size: SizeType): Integer;
       external name 'memcmp';
     function  MemCompCase (const s1, s2; Size: SizeType): Boolean;
       attribute (name = '_p_MemCompCase'); external;
     
     procedure UpCaseString    (var s: String); attribute (name
       = '_p_UpCaseString'); external;
     procedure LoCaseString    (var s: String); attribute (name
       = '_p_LoCaseString'); external;
     function  UpCaseStr       (const s: String): TString; attribute
       (name = '_p_UpCaseStr'); external;
     function  LoCaseStr       (const s: String): TString; attribute
       (name = '_p_LoCaseStr'); external;
     
     function  StrEqualCase    (const s1, s2: String): Boolean; attribute
       (name = '_p_StrEqualCase'); external;
     
     function  Pos             (const SubString, s: String): Integer;
       attribute (name = '_p_Pos'); external;
     function  PosChar         (const ch: Char; const s: String):
       Integer; attribute (name = '_p_PosChar'); external;
     function  LastPos         (const SubString, s: String): Integer;
       attribute (name = '_p_LastPos'); external;
     function  PosCase         (const SubString, s: String): Integer;
       attribute (name = '_p_PosCase'); external;
     function  LastPosCase     (const SubString, s: String): Integer;
       attribute (name = '_p_LastPosCase'); external;
     function  CharPos         (const Chars: CharSet; const s: String):
       Integer; attribute (name = '_p_CharPos'); external;
     function  LastCharPos     (const Chars: CharSet; const s: String):
       Integer; attribute (name = '_p_LastCharPos'); external;
     
     function  PosFrom         (const SubString, s: String; From:
       Integer): Integer; attribute (name = '_p_PosFrom'); external;
     function  LastPosTill     (const SubString, s: String; Till:
       Integer): Integer; attribute (name = '_p_LastPosTill'); external;
     function  PosFromCase     (const SubString, s: String; From:
       Integer): Integer; attribute (name = '_p_PosFromCase'); external;
     function  LastPosTillCase (const SubString, s: String; Till:
       Integer): Integer; attribute (name = '_p_LastPosTillCase');
       external;
     function  CharPosFrom     (const Chars: CharSet; const s: String;
       From: Integer): Integer; attribute (name = '_p_CharPosFrom');
       external;
     function  LastCharPosTill (const Chars: CharSet; const s: String;
       Till: Integer): Integer; attribute (name = '_p_LastCharPosTill');
       external;
     
     function  IsPrefix        (const Prefix, s: String): Boolean;
       attribute (name = '_p_IsPrefix'); external;
     function  IsSuffix        (const Suffix, s: String): Boolean;
       attribute (name = '_p_IsSuffix'); external;
     function  IsPrefixCase    (const Prefix, s: String): Boolean;
       attribute (name = '_p_IsPrefixCase'); external;
     function  IsSuffixCase    (const Suffix, s: String): Boolean;
       attribute (name = '_p_IsSuffixCase'); external;
     
     function  CStringLength      (Src: CString): SizeType; attribute
       (inline, name = '_p_CStringLength'); external;
     function  CStringEnd         (Src: CString): CString; attribute
       (inline, name = '_p_CStringEnd'); external;
     function  CStringNew         (Src: CString): CString; attribute
       (name = '_p_CStringNew'); external;
     function  CStringComp        (s1, s2: CString): Integer; attribute
       (name = '_p_CStringComp'); external;
     function  CStringCaseComp    (s1, s2: CString): Integer; attribute
       (name = '_p_CStringCaseComp'); external;
     function  CStringLComp       (s1, s2: CString; MaxLen: SizeType):
       Integer; attribute (name = '_p_CStringLComp'); external;
     function  CStringLCaseComp   (s1, s2: CString; MaxLen: SizeType):
       Integer; attribute (name = '_p_CStringLCaseComp'); external;
     function  CStringCopy        (Dest, Source: CString): CString;
       attribute (ignorable, name = '_p_CStringCopy'); external;
     function  CStringCopyEnd     (Dest, Source: CString): CString;
       attribute (ignorable, name = '_p_CStringCopyEnd'); external;
     function  CStringLCopy       (Dest, Source: CString; MaxLen:
       SizeType): CString; attribute (ignorable, name
       = '_p_CStringLCopy'); external;
     function  CStringMove        (Dest, Source: CString; Count:
       SizeType): CString; attribute (ignorable, name
       = '_p_CStringMove'); external;
     function  CStringCat         (Dest, Source: CString): CString;
       attribute (ignorable, name = '_p_CStringCat'); external;
     function  CStringLCat        (Dest, Source: CString; MaxLen:
       SizeType): CString; attribute (ignorable, name
       = '_p_CStringLCat'); external;
     function  CStringChPos       (Src: CString; ch: Char): CString;
       attribute (inline, name = '_p_CStringChPos'); external;
     function  CStringLastChPos   (Src: CString; ch: Char): CString;
       attribute (inline, name = '_p_CStringLastChPos'); external;
     function  CStringPos         (s, SubString: CString): CString;
       attribute (name = '_p_CStringPos'); external;
     function  CStringLastPos     (s, SubString: CString): CString;
       attribute (name = '_p_CStringLastPos'); external;
     function  CStringCasePos     (s, SubString: CString): CString;
       attribute (name = '_p_CStringCasePos'); external;
     function  CStringLastCasePos (s, SubString: CString): CString;
       attribute (name = '_p_CStringLastCasePos'); external;
     function  CStringUpCase      (s: CString): CString; attribute (name
       = '_p_CStringUpCase'); external;
     function  CStringLoCase      (s: CString): CString; attribute (name
       = '_p_CStringLoCase'); external;
     function  CStringIsEmpty     (s: CString): Boolean; attribute (name
       = '_p_CStringIsEmpty'); external;
     function  NewCString         (const Source: String): CString;
       attribute (name = '_p_NewCString'); external;
     function  CStringCopyString  (Dest: CString; const Source: String):
       CString; attribute (name = '_p_CStringCopyString'); external;
     procedure CopyCString        (Source: CString; var Dest: String);
       attribute (name = '_p_CopyCString'); external;
     
     function  NewString       (const s: String): PString; attribute
       (name = '_p_NewString'); external;
     procedure DisposeString   (p: PString); external name '_p_Dispose';
     
     procedure SetString       (var s: String; Buffer: PChar; Count:
       Integer); attribute (name = '_p_SetString'); external;
     function  StringOfChar    (ch: Char; Count: Integer) = s: TString;
       attribute (name = '_p_StringOfChar'); external;
     
     procedure TrimLeft        (var s: String); attribute (name
       = '_p_TrimLeft'); external;
     procedure TrimRight       (var s: String); attribute (name
       = '_p_TrimRight'); external;
     procedure TrimBoth        (var s: String); attribute (name
       = '_p_TrimBoth'); external;
     function  TrimLeftStr     (const s: String): TString; attribute
       (name = '_p_TrimLeftStr'); external;
     function  TrimRightStr    (const s: String): TString; attribute
       (name = '_p_TrimRightStr'); external;
     function  TrimBothStr     (const s: String): TString; attribute
       (name = '_p_TrimBothStr'); external;
     function  LTrim           (const s: String): TString; external
       name '_p_TrimLeftStr';
     
     function  GetStringCapacity (const s: String): Integer; attribute
       (name = '_p_GetStringCapacity'); external;
     
     { A shortcut for a common use of WriteStr as a function }
     function  Integer2String (i: Integer): Str64; attribute (name
       = '_p_Integer2String'); external;
     
     { Convert integer n to string in base Base. }
     function  Integer2StringBase (n: LongestInt; Base:
       TInteger2StringBase): TString; attribute (name
       = '_p_Integer2StringBase'); external;
     
     { Convert integer n to string in base Base, with sign, optionally in
       uppercase representation and with printed base, padded with
       leading zeroes between [<Sign>]<Base># and the actual digits to
       specified Width. }
     function  Integer2StringBaseExt (n: LongestInt; Base:
       TInteger2StringBase; Width: TInteger2StringWidth; Upper: Boolean;
       PrintBase: Boolean): TString; attribute (name
       = '_p_Integer2StringBaseExt'); external;
     
     { String handling routines (higher level), from string2.pas }
     
     type
       PChars0 = ^TChars0;
       TChars0 = array [0 .. MaxVarSize div SizeOf (Char) - 1] of Char;
     
       PChars = ^TChars;
       TChars = packed array [1 .. MaxVarSize div SizeOf (Char)] of Char;
     
       { Under development. Interface subject to change.
         Use with caution. }
       { When a const or var AnyString parameter is passed, internally
         these records are passed as const parameters. Value AnyString
         parameters are passed like value string parameters. }
       ConstAnyString = record
         Length: Integer;
         Chars: PChars
       end;
     
       { Capacity is the allocated space (used internally). Count is the
         actual number of environment strings. The CStrings array
         contains the environment strings, terminated by a nil pointer,
         which is not counted in Count. @CStrings can be passed to libc
         routines like execve which expect an environment (see
         GetCEnvironment). }
       PEnvironment = ^TEnvironment;
       TEnvironment (Capacity: Integer) = record
         Count: Integer;
         CStrings: array [1 .. Capacity + 1] of CString
       end;
     
     var
       Environment: PEnvironment; attribute (name = '_p_Environment');
       external;
     
     { Get an environment variable. If it does not exist, GetEnv returns
       the empty string, which can't be distinguished from a variable
       with an empty value, while CStringGetEnv returns nil then. Note,
       Dos doesn't know empty environment variables, but treats them as
       non-existing, and does not distinguish case in the names of
       environment variables. However, even under Dos, empty environment
       variables and variable names with different case can now be set
       and used within GPC programs. }
     function  GetEnv (const EnvVar: String): TString; attribute (name
       = '_p_GetEnv'); external;
     function  CStringGetEnv (EnvVar: CString): CString; attribute (name
       = '_p_CStringGetEnv'); external;
     
     { Sets an environment variable with the name given in VarName to the
       value Value. A previous value, if any, is overwritten. }
     procedure SetEnv (const VarName, Value: String); attribute (name
       = '_p_SetEnv'); external;
     
     { Un-sets an environment variable with the name given in VarName. }
     procedure UnSetEnv (const VarName: String); attribute (name
       = '_p_UnSetEnv'); external;
     
     { Returns @Environment^.CStrings, converted to PCStrings, to be
       passed to libc routines like execve which expect an environment. }
     function  GetCEnvironment: PCStrings; attribute (name
       = '_p_GetCEnvironment'); external;
     
     type
       FormatStringTransformType = ^function (const Format: String):
       TString;
     
     var
       FormatStringTransformPtr: FormatStringTransformType; attribute
       (name = '_p_FormatStringTransformPtr'); external;
     
     { Runtime error and signal handling routines, from error.pas }
     
     const
       EAssert = 306;
       EAssertString = 307;
       EOpen = 405;
       EMMap = 408;
       ERead = 413;
       EWrite = 414;
       EWriteReadOnly = 422;
       ENonExistentFile = 436;
       EOpenRead = 442;
       EOpenWrite = 443;
       EOpenUpdate = 444;
       EReading = 464;
       EWriting = 466;
       ECannotWriteAll = 467;
       ECannotFork = 600;
       ECannotSpawn = 601;
       EProgramNotFound = 602;
       EProgramNotExecutable = 603;
       EPipe = 604;
       EPrinterRead = 610;
       EIOCtl = 630;
       EConvertError = 875;
       ELibraryFunction = 952;
       EExitReturned = 953;
     
       RuntimeErrorExitValue = 42;
     
     var
       { Error number (after runtime error) or exit status (after Halt)
         or 0 (during program run and after succesful termination). }
       ExitCode: Integer; attribute (name = '_p_ExitCode'); external;
     
       { Contains the address of the code where a runtime occurred, nil
         if no runtime error occurred. }
       ErrorAddr: Pointer; attribute (name = '_p_ErrorAddr'); external;
     
       { Error message }
       ErrorMessageString: TString; attribute (name
       = '_p_ErrorMessageString'); external;
     
       { String parameter to some error messages, *not* the text of the
         error message (the latter can be obtained with
         GetErrorMessage). }
       InOutResString: PString; attribute (name = '_p_InOutResString');
       external;
     
       { Optional libc error string to some error messages. }
       InOutResCErrorString: PString; attribute (name
       = '_p_InOutResCErrorString'); external;
     
       RTSErrorFD: Integer; attribute (name = '_p_ErrorFD'); external;
       RTSErrorFileName: PString; attribute (name = '_p_ErrorFileName');
       external;
     
     function  GetErrorMessage                 (n: Integer): CString;
       attribute (name = '_p_GetErrorMessage'); external;
     procedure RuntimeError                    (n: Integer); attribute
       (noreturn, name = '_p_RuntimeError'); external;
     procedure RuntimeErrorErrNo               (n: Integer); attribute
       (noreturn, name = '_p_RuntimeErrorErrNo'); external;
     procedure RuntimeErrorInteger             (n: Integer; i: MedInt);
       attribute (noreturn, name = '_p_RuntimeErrorInteger'); external;
     procedure RuntimeErrorCString             (n: Integer; s: CString);
       attribute (noreturn, name = '_p_RuntimeErrorCString'); external;
     procedure InternalError                   (n: Integer); attribute
       (noreturn, name = '_p_InternalError'); external;
     procedure InternalErrorInteger            (n: Integer; i: MedInt);
       attribute (noreturn, name = '_p_InternalErrorInteger'); external;
     procedure InternalErrorCString            (n: Integer; s: CString);
       attribute (noreturn, name = '_p_InternalErrorCString'); external;
     procedure RuntimeWarning                  (Message: CString);
       attribute (name = '_p_RuntimeWarning'); external;
     procedure RuntimeWarningInteger           (Message: CString; i:
       MedInt); attribute (name = '_p_RuntimeWarningInteger'); external;
     procedure RuntimeWarningCString           (Message: CString; s:
       CString); attribute (name = '_p_RuntimeWarningCString'); external;
     procedure DebugStatement                  (const FileName: String;
       Line: Integer); attribute (name = '_p_DebugStatement'); external;
     
     procedure IOError                         (n: Integer; ErrNoFlag:
       Boolean); attribute (iocritical, name = '_p_IOError'); external;
     procedure IOErrorInteger                  (n: Integer; i: MedInt;
       ErrNoFlag: Boolean); attribute (iocritical, name
       = '_p_IOErrorInteger'); external;
     procedure IOErrorCString                  (n: Integer; s: CString;
       ErrNoFlag: Boolean); attribute (iocritical, name
       = '_p_IOErrorCString'); external;
     procedure IOErrorFile                     (n: Integer; protected var
       f: AnyFile; ErrNoFlag: Boolean); attribute (iocritical, name
       = '_p_IOErrorFile'); external;
     
     function  GetIOErrorMessage: TString; attribute (name
       = '_p_GetIOErrorMessage'); external;
     procedure CheckInOutRes; attribute (name = '_p_CheckInOutRes');
       external;
     
     { Registers a procedure to be called to restore the terminal for
       another process that accesses the terminal, or back for the
       program itself. Used e.g. by the CRT unit. The procedures must
       allow for being called multiple times in any order, even at the
       end of the program (see the comment for RestoreTerminal). }
     procedure RegisterRestoreTerminal (ForAnotherProcess: Boolean;
       procedure Proc); attribute (name = '_p_RegisterRestoreTerminal');
       external;
     
     { Unregisters a procedure registered with RegisterRestoreTerminal.
       Returns False if the procedure had not been registered, and True
       if it had been registered and was unregistered successfully. }
     function  UnregisterRestoreTerminal (ForAnotherProcess: Boolean;
       procedure Proc): Boolean; attribute (name
       = '_p_UnregisterRestoreTerminal'); external;
     
     { Calls the procedures registered by RegisterRestoreTerminal. When
       restoring the terminal for another process, the procedures are
       called in the opposite order of registration. When restoring back
       for the program, they are called in the order of registration.
     
       RestoreTerminal (True) will also be called at the end of the
       program, before outputting any runtime error message. It can also
       be used if you want to write an error message and exit the program
       (especially when using e.g. the CRT unit). For this purpose, to
       avoid side effects, call RestoreTerminal immediately before
       writing the error message (to StdErr, not to Output!), and then
       exit the program (e.g. with Halt). }
     procedure RestoreTerminal (ForAnotherProcess: Boolean); attribute
       (name = '_p_RestoreTerminal'); external;
     
     procedure AtExit (procedure Proc); attribute (name = '_p_AtExit');
       external;
     
     function  ReturnAddr2Hex (p: Pointer): TString; attribute (name
       = '_p_ReturnAddr2Hex'); external;
     
     { This function is used to write error messages etc. It does not use
       the Pascal I/O system here because it is usually called at the
       very end of a program after the Pascal I/O system has been shut
       down. }
     function  WriteErrorMessage (const s: String; StdErrFlag: Boolean):
       Boolean; attribute (name = '_p_WriteErrorMessage'); external;
     
     procedure SetReturnAddress (Address: Pointer); attribute (name
       = '_p_SetReturnAddress'); external;
     procedure RestoreReturnAddress; attribute (name
       = '_p_RestoreReturnAddress'); external;
     
     { Returns a description for a signal }
     function  StrSignal (Signal: Integer): TString; attribute (name
       = '_p_StrSignal'); external;
     
     { Installs some signal handlers that cause runtime errors on certain
       signals. This procedure runs only once, and returns immediately
       when called again (so you can't use it to set the signals again if
       you changed them meanwhile). @@Does not work on all systems (since
       the handler might have too little stack space). }
     procedure InstallDefaultSignalHandlers; attribute (name
       = '_p_InstallDefaultSignalHandlers'); external;
     
     var
       { Signal actions }
       SignalDefault: TSignalHandler; attribute (const); external
       name '_p_SIG_DFL';
       SignalIgnore : TSignalHandler; attribute (const); external
       name '_p_SIG_IGN';
       SignalError  : TSignalHandler; attribute (const); external
       name '_p_SIG_ERR';
     
       { Signals. The constants are set to the signal numbers, and
         are 0 for signals not defined. }
       { POSIX signals }
       SigHUp   : Integer; attribute (const); external name '_p_SIGHUP';
       SigInt   : Integer; attribute (const); external name '_p_SIGINT';
       SigQuit  : Integer; attribute (const); external name '_p_SIGQUIT';
       SigIll   : Integer; attribute (const); external name '_p_SIGILL';
       SigAbrt  : Integer; attribute (const); external name '_p_SIGABRT';
       SigFPE   : Integer; attribute (const); external name '_p_SIGFPE';
       SigKill  : Integer; attribute (const); external name '_p_SIGKILL';
       SigSegV  : Integer; attribute (const); external name '_p_SIGSEGV';
       SigPipe  : Integer; attribute (const); external name '_p_SIGPIPE';
       SigAlrm  : Integer; attribute (const); external name '_p_SIGALRM';
       SigTerm  : Integer; attribute (const); external name '_p_SIGTERM';
       SigUsr1  : Integer; attribute (const); external name '_p_SIGUSR1';
       SigUsr2  : Integer; attribute (const); external name '_p_SIGUSR2';
       SigChld  : Integer; attribute (const); external name '_p_SIGCHLD';
       SigCont  : Integer; attribute (const); external name '_p_SIGCONT';
       SigStop  : Integer; attribute (const); external name '_p_SIGSTOP';
       SigTStp  : Integer; attribute (const); external name '_p_SIGTSTP';
       SigTTIn  : Integer; attribute (const); external name '_p_SIGTTIN';
       SigTTOu  : Integer; attribute (const); external name '_p_SIGTTOU';
     
       { Non-POSIX signals }
       SigTrap  : Integer; attribute (const); external name '_p_SIGTRAP';
       SigIOT   : Integer; attribute (const); external name '_p_SIGIOT';
       SigEMT   : Integer; attribute (const); external name '_p_SIGEMT';
       SigBus   : Integer; attribute (const); external name '_p_SIGBUS';
       SigSys   : Integer; attribute (const); external name '_p_SIGSYS';
       SigStkFlt: Integer; attribute (const); external
       name '_p_SIGSTKFLT';
       SigUrg   : Integer; attribute (const); external name '_p_SIGURG';
       SigIO    : Integer; attribute (const); external name '_p_SIGIO';
       SigPoll  : Integer; attribute (const); external name '_p_SIGPOLL';
       SigXCPU  : Integer; attribute (const); external name '_p_SIGXCPU';
       SigXFSz  : Integer; attribute (const); external name '_p_SIGXFSZ';
       SigVTAlrm: Integer; attribute (const); external
       name '_p_SIGVTALRM';
       SigProf  : Integer; attribute (const); external name '_p_SIGPROF';
       SigPwr   : Integer; attribute (const); external name '_p_SIGPWR';
       SigInfo  : Integer; attribute (const); external name '_p_SIGINFO';
       SigLost  : Integer; attribute (const); external name '_p_SIGLOST';
       SigWinCh : Integer; attribute (const); external
       name '_p_SIGWINCH';
     
       { Signal subcodes (only used on some systems, -1 if not used) }
       FPEIntegerOverflow      : Integer; attribute (const); external
       name '_p_FPE_INTOVF_TRAP';
       FPEIntegerDivisionByZero: Integer; attribute (const); external
       name '_p_FPE_INTDIV_TRAP';
       FPESubscriptRange       : Integer; attribute (const); external
       name '_p_FPE_SUBRNG_TRAP';
       FPERealOverflow         : Integer; attribute (const); external
       name '_p_FPE_FLTOVF_TRAP';
       FPERealDivisionByZero   : Integer; attribute (const); external
       name '_p_FPE_FLTDIV_TRAP';
       FPERealUnderflow        : Integer; attribute (const); external
       name '_p_FPE_FLTUND_TRAP';
       FPEDecimalOverflow      : Integer; attribute (const); external
       name '_p_FPE_DECOVF_TRAP';
     
     { Routines called implicitly by the compiler. }
     procedure GPC_Assert (Condition: Boolean; const Message: String);
       attribute (name = '_p_Assert'); external;
     function  ObjectTypeIs (Left, Right: PObjectType): Boolean;
       attribute (const, name = '_p_ObjectTypeIs'); external;
     procedure ObjectTypeAsError; attribute (noreturn, name
       = '_p_ObjectTypeAsError'); external;
     procedure DisposeNilError; attribute (noreturn, name
       = '_p_DisposeNilError'); external;
     procedure CaseNoMatchError; attribute (noreturn, name
       = '_p_CaseNoMatchError'); external;
     procedure RangeCheckError; attribute (noreturn, name
       = '_p_RangeCheckError'); external;
     procedure SubrangeError; attribute (noreturn, name
       = '_p_SubrangeError'); external;
     procedure ModRangeError; attribute (noreturn, name
       = '_p_ModRangeError'); external;
     
     { Time and date routines, from time.pas }
     
     const
       InvalidYear = -MaxInt;
     
     var
       { DayOfWeekName is a constant and therefore does not respect the
         locale. Therefore, it's recommended to use FormatTime instead. }
       DayOfWeekName: array [0 .. 6] of String [9]; attribute (const,
       name = '_p_DayOfWeekName'); external;
     
       { MonthName is a constant and therefore does not respect the
         locale. Therefore, it's recommended to use FormatTime instead. }
       MonthName: array [1 .. 12] of String [9]; attribute (const, name
       = '_p_MonthName'); external;
     
     function  GetDayOfWeek (Day, Month, Year: Integer): Integer;
       attribute (name = '_p_GetDayOfWeek'); external;
     function  GetDayOfYear (Day, Month, Year: Integer): Integer;
       attribute (name = '_p_GetDayOfYear'); external;
     function  GetSundayWeekOfYear (Day, Month, Year: Integer): Integer;
       attribute (name = '_p_GetSundayWeekOfYear'); external;
     function  GetMondayWeekOfYear (Day, Month, Year: Integer): Integer;
       attribute (name = '_p_GetMondayWeekOfYear'); external;
     procedure GetISOWeekOfYear (Day, Month, Year: Integer; var ISOWeek,
       ISOWeekYear: Integer); attribute (name = '_p_GetISOWeekOfYear');
       external;
     procedure UnixTimeToTimeStamp (UnixTime: UnixTimeType; var
       aTimeStamp: TimeStamp); attribute (name
       = '_p_UnixTimeToTimeStamp'); external;
     function  TimeStampToUnixTime (protected var aTimeStamp: TimeStamp):
       UnixTimeType; attribute (name = '_p_TimeStampToUnixTime');
       external;
     function  GetMicroSecondTime: MicroSecondTimeType; attribute (name
       = '_p_GetMicroSecondTime'); external;
     
     { Is the year a leap year? }
     function  IsLeapYear (Year: Integer): Boolean; attribute (name
       = '_p_IsLeapYear'); external;
     
     { Returns the length of the month, taking leap years into account. }
     function  MonthLength (Month, Year: Integer): Integer; attribute
       (name = '_p_MonthLength'); external;
     
     { Formats a TimeStamp value according to a Format string. The format
       string can contain date/time items consisting of %, followed by
       the specifiers listed below. All characters outside of these items
       are copied to the result unmodified. The specifiers correspond to
       those of the C function strftime(), including POSIX.2 and glibc
       extensions and some more extensions. The extensions are also
       available on systems whose strftime() doesn't support them.
     
       The following modifiers may appear after the %:
     
       _  The item is left padded with spaces to the given or default
            width.
     
       -  The item is not padded at all.
     
       0  The item is left padded with zeros to the given or default
            width.
     
       /  The item is right trimmed if it is longer than the given
            width.
     
       ^  The item is converted to upper case.
     
       ~  The item is converted to lower case.
     
       After zero or more of these flags, an optional width may be
       specified for padding and trimming. It must be given as a decimal
       number (not starting with 0 since 0 has a meaning of its own,
       see above).
     
       Afterwards, the following optional modifiers may follow. Their
       meaning is locale-dependent, and many systems and locales just
       ignore them.
     
       E  Use the locale's alternate representation for date and time.
            In a Japanese locale, for example, %Ex might yield a date
            format based on the Japanese Emperors' reigns.
     
       O  Use the locale's alternate numeric symbols for numbers. This
            modifier applies only to numeric format specifiers.
     
       Finally, exactly one of the following specifiers must appear. The
       padding rules listed here are the defaults that can be overriden
       with the modifiers listed above.
     
       a  The abbreviated weekday name according to the current locale.
     
       A  The full weekday name according to the current locale.
     
       b  The abbreviated month name according to the current locale.
     
       B  The full month name according to the current locale.
     
       c  The preferred date and time representation for the current
            locale.
     
       C  The century of the year. This is equivalent to the greatest
            integer not greater than the year divided by 100.
     
       d  The day of the month as a decimal number (01 .. 31).
     
       D  The date using the format %m/%d/%y. NOTE: Don't use this
            format if it can be avoided. Things like this caused Y2K
            bugs!
     
       e  The day of the month like with %d, but padded with blanks
            ( 1 .. 31).
     
       F  The date using the format %Y-%m-%d. This is the form
            specified in the ISO 8601 standard and is the preferred form
            for all uses.
     
       g  The year corresponding to the ISO week number, but without
            the century (00 .. 99). This has the same format and
            value as y, except that if the ISO week number (see V)
            belongs to the previous or next year, that year is used
            instead. NOTE: Don't use this format if it can be avoided.
            Things like this caused Y2K bugs!
     
       G  The year corresponding to the ISO week number. This has the
            same format and value as Y, except that if the ISO week
            number (see V) belongs to the previous or next year, that
            year is used instead.
     
       h  The abbreviated month name according to the current locale.
            This is the same as b.
     
       H  The hour as a decimal number, using a 24-hour clock
            (00 .. 23).
     
       I  The hour as a decimal number, using a 12-hour clock
            (01 .. 12).
     
       j  The day of the year as a decimal number (001 .. 366).
     
       k  The hour as a decimal number, using a 24-hour clock like H,
            but padded with blanks ( 0 .. 23).
     
       l  The hour as a decimal number, using a 12-hour clock like I,
            but padded with blanks ( 1 .. 12).
     
       m  The month as a decimal number (01 .. 12).
     
       M  The minute as a decimal number (00 .. 59).
     
       n  A single newline character.
     
       p  Either AM or PM, according to the given time value; or
            the corresponding strings for the current locale. Noon is
            treated as PM and midnight as AM.
     
       P  Either am or pm, according to the given time value; or
            the corresponding strings for the current locale, printed in
            lowercase characters. Noon is treated as pm and midnight as
            am.
     
       Q  The fractional part of the second. This format has special
            effects on the modifiers. The width, if given, determines the
            number of digits to output. Therefore, no actual clipping or
            trimming is done. However, if padding with spaces is
            specified, any trailing (i.e., right!) zeros are converted to
            spaces, and if "no padding" is specified, they are removed.
            The default is "padding with zeros", i.e. trailing zeros are
            left unchanged. The digits are cut when necessary without
            rounding (otherwise, the value would not be consistent with
            the seconds given by S and s). Note that GPC's TimeStamp
            currently provides for microsecond resolution, so there are
            at most 6 valid digits (which is also the default width), any
            further digits will be 0 (but if TimeStamp will ever change,
            this format will be adjusted). However, the actual resolution
            provided by the operating system via GetTimeStamp etc. may be
            far lower (e.g., ~1/18s under Dos).
     
       r  The complete time using the AM/PM format of the current
            locale.
     
       R  The hour and minute in decimal numbers using the format
            %H:%M.
     
       s  Unix time, i.e. the number of seconds since the epoch, i.e.,
            since 1970-01-01 00:00:00 UTC. Leap seconds are not counted
            unless leap second support is available.
     
       S  The seconds as a decimal number (00 .. 60).
     
       t  A single tab character.
     
       T  The time using decimal numbers using the format %H:%M:%S.
     
       u  The day of the week as a decimal number (1 .. 7), Monday
            being 1.
     
       U  The week number of the current year as a decimal number
            (00 .. 53), starting with the first Sunday as the first
            day of the first week. Days preceding the first Sunday in the
            year are considered to be in week 00.
     
       V  The ISO 8601:1988 week number as a decimal number
            (01 .. 53). ISO weeks start with Monday and end with
            Sunday. Week 01 of a year is the first week which has the
            majority of its days in that year; this is equivalent to the
            week containing the year's first Thursday, and it is also
            equivalent to the week containing January 4. Week 01 of a
            year can contain days from the previous year. The week before
            week 01 of a year is the last week (52 or 53) of the
            previous year even if it contains days from the new year.
     
       w  The day of the week as a decimal number (0 .. 6), Sunday
            being 0.
     
       W  The week number of the current year as a decimal number
            (00 .. 53), starting with the first Monday as the first
            day of the first week. All days preceding the first Monday in
            the year are considered to be in week 00.
     
       x  The preferred date representation for the current locale, but
            without the time.
     
       X  The preferred time representation for the current locale, but
            with no date.
     
       y  The year without a century as a decimal number
            (00 .. 99). This is equivalent to the year modulo 100.
            NOTE: Don't use this format if it can be avoided. Things like
            this caused Y2K bugs!
     
       Y  The year as a decimal number, using the Gregorian calendar.
            Years before the year 1 are numbered 0, -1, and so on.
     
       z  RFC 822/ISO 8601:1988 style numeric time zone (e.g., -0600
            or +0100), or nothing if no time zone is determinable.
     
       Z  The time zone abbreviation (empty if the time zone can't be
            determined).
     
       %  (i.e., an item %%) A literal % character. }
     function  FormatTime (const Time: TimeStamp; const Format: String):
       TString; attribute (name = '_p_FormatTime'); external;
     
     { Pseudo random number generator, from random.pas }
     
     type
       RandomSeedType = Cardinal attribute (Size = 32);
       RandomizeType  = ^procedure;
       SeedRandomType = ^procedure (Seed: RandomSeedType);
       RandRealType   = ^function: LongestReal;
       RandIntType    = ^function (MaxValue: LongestCard): LongestCard;
     
     var
       RandomizePtr : RandomizeType; attribute (name
       = '_p_RandomizePtr'); external;
       SeedRandomPtr: SeedRandomType; attribute (name
       = '_p_SeedRandomPtr'); external;
       RandRealPtr  : RandRealType; attribute (name = '_p_RandRealPtr');
       external;
       RandIntPtr   : RandIntType; attribute (name = '_p_RandIntPtr');
       external;
     
     procedure SeedRandom (Seed: RandomSeedType); attribute (name
       = '_p_SeedRandom'); external;
     
     { File name routines, from filename.pas }
     
     { Define constants for different systems:
     
       OSDosFlag:         flag to indicate whether the target system is
                          Dos
     
       QuotingCharacter:  the character used to quote wild cards and
                          other special characters (#0 if not available)
     
       PathSeparator:     the separator of multiple paths, e.g. in the
                          PATH environment variable
     
       DirSeparator:      the separator of the directories within a full
                          file name
     
       DirSeparators:     a set of all possible directory and drive name
                          separators
     
       ExtSeparator:      the separator of a file name extension
     
       DirRoot:           the name of the root directory
     
       DirSelf:           the name of a directory in itself
     
       DirParent:         the name of the parent directory
     
       MaskNoStdDir:      a file name mask that matches all names except
                          the standard directories DirSelf and DirParent
     
       NullDeviceName:    the full file name of the null device
     
       TtyDeviceName:     the full file name of the current Tty
     
       ConsoleDeviceName: the full file name of the system console. On
                          Dos systems, this is the same as the Tty, but
                          on systems that allow remote login, this is a
                          different thing and may reach a completely
                          different user than the one running the
                          program, so use it with care.
     
       EnvVarCharsFirst:  the characters accepted at the beginning of the
                          name of an environment variable without quoting
     
       EnvVarChars:       the characters accepted in the name of an
                          environment variable without quoting
     
       PathEnvVar:        the name of the environment variable which
                          (usually) contains the executable search path
     
       ShellEnvVar:       the name of the environment variable which
                          (usually) contains the path of the shell
                          executable (see GetShellPath)
     
       ShellExecCommand:  the option to the (default) shell to execute
                          the command specified in the following argument
                          (see GetShellPath)
     
       ConfigFileMask:    a mask for the option file name as returned by
                          ConfigFileName
     
       FileNamesCaseSensitive:
                          flag to indicate whether file names are case
                          sensitive }
     
     const
       UnixShellEnvVar        = 'SHELL';
       UnixShellExecCommand   = '-c';
     
     {$ifdef __OS_DOS__}
     
     {$if defined (__CYGWIN__) or defined(__MSYS__)}
       {$define __POSIX_WIN32__}
     {$endif}
     
     const
       OSDosFlag              = True;
       QuotingCharacter       = #0;
       PathSeparator          = {$ifdef __POSIX_WIN32__} ':' {$else} ';'
       {$endif};
       DirSeparator           = '\';
       DirSeparators          = [':', '\', '/'];
       ExtSeparator           = '.';
       DirRoot                = '\';
       DirSelf                = '.';
       DirParent              = '..';
       MaskNoStdDir           = '{*,.[^.]*,..?*}';
       NullDeviceName         = 'nul';
       TtyDeviceName          = 'con';
       ConsoleDeviceName      = 'con';
       EnvVarCharsFirst       = ['A' .. 'Z', 'a' .. 'z', '_'];
       EnvVarChars            = EnvVarCharsFirst + ['0' .. '9'];
       PathEnvVar             = 'PATH';
       ShellEnvVar            = 'COMSPEC';
       ShellExecCommand       = '/c';
       ConfigFileMask         = '*.cfg';
       FileNamesCaseSensitive = False;
     
     {$else}
     
     const
       OSDosFlag              = False;
       QuotingCharacter       = '\';
       PathSeparator          = ':';
       DirSeparator           = '/';
       DirSeparators          = ['/'];
       ExtSeparator           = '.';
       DirRoot                = '/';
       DirSelf                = '.';
       DirParent              = '..';
       MaskNoStdDir           = '{*,.[^.]*,..?*}';
       NullDeviceName         = '/dev/null';
       TtyDeviceName          = '/dev/tty';
       ConsoleDeviceName      = '/dev/console';
       EnvVarCharsFirst       = ['A' .. 'Z', 'a' .. 'z', '_'];
       EnvVarChars            = EnvVarCharsFirst + ['0' .. '9'];
       PathEnvVar             = 'PATH';
       ShellEnvVar            = UnixShellEnvVar;
       ShellExecCommand       = UnixShellExecCommand;
       ConfigFileMask         = '.*';
       FileNamesCaseSensitive = True;
     
     {$endif}
     
     const
       WildCardChars = ['*', '?', '[', ']'];
       FileNameSpecialChars = (WildCardChars + SpaceCharacters +
       ['{', '}', '$', QuotingCharacter]) - DirSeparators;
     
     type
       DirPtr = Pointer;
     
     { Convert ch to lower case if FileNamesCaseSensitive is False, leave
       it unchanged otherwise. }
     function  FileNameLoCase (ch: Char): Char; attribute (name
       = '_p_FileNameLoCase'); external;
     
     { Change a file name to use the OS dependent directory separator }
     function  Slash2OSDirSeparator (const s: String): TString; attribute
       (name = '_p_Slash2OSDirSeparator'); external;
     
     { Change a file name to use '/' as directory separator }
     function  OSDirSeparator2Slash (const s: String): TString; attribute
       (name = '_p_OSDirSeparator2Slash'); external;
     
     { Like Slash2OSDirSeparator for CStrings. *Note*: overwrites the
       CString }
     function  Slash2OSDirSeparator_CString (s: CString): CString;
       attribute (name = '_p_Slash2OSDirSeparator_CString'); external;
     
     { Like OSDirSeparator2Slash for CStrings. *Note*: overwrites the
       CString }
     function  OSDirSeparator2Slash_CString (s: CString): CString;
       attribute (name = '_p_OSDirSeparator2Slash_CString'); external;
     
     { Add a DirSeparator to the end of s, if there is not already one
       and s denotes an existing directory }
     function  AddDirSeparator (const s: String): TString; attribute
       (name = '_p_AddDirSeparator'); external;
     
     { Like AddDirSeparator, but also if the directory does not exist }
     function  ForceAddDirSeparator (const s: String): TString; attribute
       (name = '_p_ForceAddDirSeparator'); external;
     
     { Remove all trailing DirSeparators from s, if there are any, as
       long as removing them doesn't change the meaning (i.e., they don't
       denote the root directory. }
     function  RemoveDirSeparator (const s: String): TString; attribute
       (name = '_p_RemoveDirSeparator'); external;
     
     { Returns the current directory using OS dependent directory
       separators }
     function  GetCurrentDirectory: TString; attribute (name
       = '_p_GetCurrentDirectory'); external;
     
     { Returns a directory suitable for storing temporary files using OS
       dependent directory separators. If found, the result always ends
       in DirSeparator. If no suitable directory is found, an empty
       string is returned. }
     function  GetTempDirectory: TString; attribute (name
       = '_p_GetTempDirectory'); external;
     
     { Returns a non-existing file name in the directory given. If the
       directory doesn't exist or the Directory name is empty, an I/O
       error is raised, and GetTempFileNameInDirectory returns the empty
       string. }
     function  GetTempFileNameInDirectory (const Directory: String):
       TString; attribute (iocritical, name
       = '_p_GetTempFileNameInDirectory'); external;
     
     { Returns a non-existing file name in GetTempDirectory. If no temp
       directory is found, i.e. GetTempDirectory returns the empty
       string, an I/O error is raised, and GetTempFileName returns the
       empty string as well. }
     function  GetTempFileName: TString; attribute (iocritical, name
       = '_p_GetTempFileName'); external;
     
     { The same as GetTempFileName, but returns a CString allocated from
       the heap. }
     function  GetTempFileName_CString: CString; attribute (iocritical,
       name = '_p_GetTempFileName_CString'); external;
     
     { Get the external name of a file }
     function  FileName (protected var f: AnyFile): TString; attribute
       (name = '_p_FileName'); external;
     
     { Returns True if the given file name is an existing plain file }
     function  FileExists      (const aFileName: String): Boolean;
       attribute (name = '_p_FileExists'); external;
     
     { Returns True if the given file name is an existing directory }
     function  DirectoryExists (const aFileName: String): Boolean;
       attribute (name = '_p_DirectoryExists'); external;
     
     { Returns True if the given file name is an existing file, directory
       or special file (device, pipe, socket, etc.) }
     function  PathExists      (const aFileName: String): Boolean;
       attribute (name = '_p_PathExists'); external;
     
     { If a file of the given name exists in one of the directories given
       in DirList (separated by PathSeparator), returns the full path,
       otherwise returns an empty string. If aFileName already contains
       an element of DirSeparators, returns Slash2OSDirSeparator
       (aFileName) if it exists. }
     function  FSearch (const aFileName, DirList: String): TString;
       attribute (name = '_p_FSearch'); external;
     
     { Like FSearch, but only find executable files. Under Dos, if not
       found, the function tries appending '.com', '.exe', '.bat' and
       .cmd (the last one only if $COMSPEC points to a cmd.exe), so
       you don't have to specify these extensions in aFileName (and with
       respect to portability, it might be preferable not to do so). }
     function  FSearchExecutable (const aFileName, DirList: String):
       TString; attribute (name = '_p_FSearchExecutable'); external;
     
     { Replaces all occurrences of $FOO and ~ in s by the value of
       the environment variables FOO or HOME, respectively. If a variable
       is not defined, the function returns False, and s contains the
       name of the undefined variable (or the empty string if the
       variable name is invalid, i.e., doesn't start with a character
       from EnvVarCharsFirst). Otherwise, if all variables are found, s
       contains the replaced string, and True is returned. }
     function  ExpandEnvironment (var s: String): Boolean; attribute
       (name = '_p_ExpandEnvironment'); external;
     
     { Expands the given path name to a full path name. Relative paths
       are expanded using the current directory, and occurrences of
       DirSelf and DirParent are resolved. Under Dos, the result is
       converted to lower case and a trailing ExtSeparator (except in a
       trailing DirSelf or DirParent) is removed, like Dos does. If the
       directory, i.e. the path without the file name, is invalid, the
       empty string is returned. }
     function  FExpand       (const Path: String): TString; attribute
       (name = '_p_FExpand'); external;
     
     { Like FExpand, but unquotes the directory before expanding it, and
       quotes WildCardChars again afterwards. Does not check if the
       directory is valid (because it may contain wild card characters).
       Symlinks are expanded only in the directory part, not the file
       name. }
     function  FExpandQuoted (const Path: String): TString; attribute
       (name = '_p_FExpandQuoted'); external;
     
     { FExpands Path, and then removes the current directory from it, if
       it is a prefix of it. If OnlyCurDir is set, the current directory
       will be removed only if Path denotes a file in, not below, it. }
     function  RelativePath (const Path: String; OnlyCurDir, Quoted:
       Boolean): TString; attribute (name = '_p_RelativePath'); external;
     
     { Is aFileName a UNC filename? (Always returns False on non-Dos
       systems.) }
     function  IsUNC (const aFileName: String): Boolean; attribute (name
       = '_p_IsUNC'); external;
     
     { Splits a file name into directory, name and extension. Each of
       Dir, BaseName and Ext may be Null. }
     procedure FSplit (const Path: String; var Dir, BaseName, Ext:
       String); attribute (name = '_p_FSplit'); external;
     
     { Functions that extract one or two of the parts from FSplit.
       DirFromPath returns DirSelf + DirSeparator if the path contains no
       directory. }
     function  DirFromPath     (const Path: String): TString; attribute
       (name = '_p_DirFromPath'); external;
     function  NameFromPath    (const Path: String): TString; attribute
       (name = '_p_NameFromPath'); external;
     function  ExtFromPath     (const Path: String): TString; attribute
       (name = '_p_ExtFromPath'); external;
     function  NameExtFromPath (const Path: String): TString; attribute
       (name = '_p_NameExtFromPath'); external;
     
     { Start reading a directory. If successful, a pointer is returned
       that can be used for subsequent calls to ReadDir and finally
       CloseDir. On failure, an I/O error is raised and (in case it is
       ignored) nil is returned. }
     function  OpenDir  (const DirName: String): DirPtr; attribute
       (iocritical, name = '_p_OpenDir'); external;
     
     { Reads one entry from the directory Dir, and returns the file name.
       On errors or end of directory, the empty string is returned. }
     function  ReadDir  (Dir: DirPtr): TString; attribute (name
       = '_p_ReadDir'); external;
     
     { Closes a directory opened with OpenDir. }
     procedure CloseDir (Dir: DirPtr); attribute (name = '_p_CloseDir');
       external;
     
     { Returns the first position of a non-quoted character of CharSet in
       s, or 0 if no such character exists. }
     function  FindNonQuotedChar (Chars: CharSet; const s: String; From:
       Integer): Integer; attribute (name = '_p_FindNonQuotedChar');
       external;
     
     { Returns the first occurence of SubString in s that is not quoted
       at the beginning, or 0 if no such occurence exists. }
     function  FindNonQuotedStr (const SubString, s: String; From:
       Integer): Integer; attribute (name = '_p_FindNonQuotedStr');
       external;
     
     { Does a string contain non-quoted wildcard characters? }
     function  HasWildCards (const s: String): Boolean; attribute (name
       = '_p_HasWildCards'); external;
     
     { Does a string contain non-quoted wildcard characters, braces or
       spaces? }
     function  HasWildCardsOrBraces (const s: String): Boolean; attribute
       (name = '_p_HasWildCardsOrBraces'); external;
     
     { Insert QuotingCharacter into s before any special characters }
     function  QuoteFileName (const s: String; const SpecialCharacters:
       CharSet): TString; attribute (name = '_p_QuoteFileName');
       external;
     
     { Remove QuotingCharacter from s }
     function  UnQuoteFileName (const s: String): TString; attribute
       (name = '_p_UnQuoteFileName'); external;
     
     { Splits s at non-quoted spaces and expands non-quoted braces like
       bash does. The result and its entries should be disposed after
       usage, e.g. with DisposePPStrings. }
     function  BraceExpand (const s: String): PPStrings; attribute (name
       = '_p_BraceExpand'); external;
     
     { Dispose of a PPStrings array as well as the strings it contains.
       If you want to keep the strings (by assigning them to other string
       pointers), you should instead free the PPStrings array with
       Dispose. }
     procedure DisposePPStrings (Strings: PPStrings); attribute (name
       = '_p_DisposePPStrings'); external;
     
     { Tests if a file name matches a shell wildcard pattern (?, *, []) }
     function  FileNameMatch (const Pattern, FileName: String): Boolean;
       attribute (name = '_p_FileNameMatch'); external;
     
     { FileNameMatch with BraceExpand }
     function  MultiFileNameMatch (const Pattern, FileName: String):
       Boolean; attribute (name = '_p_MultiFileNameMatch'); external;
     
     { File name globbing }
     { GlobInit is implied by Glob and MultiGlob, not by GlobOn and
       MultiGlobOn. GlobOn and MultiGlobOn must be called after GlobInit,
       Glob or MultiGlob. MultiGlob and MultiGlobOn do brace expansion,
       Glob and GlobOn do not. GlobFree frees the memory allocated by the
       globbing functions and invalidates the results in Buf. It should
       be called after globbing. }
     procedure GlobInit    (var Buf: GlobBuffer); attribute (name
       = '_p_GlobInit'); external;
     procedure Glob        (var Buf: GlobBuffer; const Pattern: String);
       attribute (name = '_p_Glob'); external;
     procedure GlobOn      (var Buf: GlobBuffer; const Pattern: String);
       attribute (name = '_p_GlobOn'); external;
     procedure MultiGlob   (var Buf: GlobBuffer; const Pattern: String);
       attribute (name = '_p_MultiGlob'); external;
     procedure MultiGlobOn (var Buf: GlobBuffer; const Pattern: String);
       attribute (name = '_p_MultiGlobOn'); external;
     procedure GlobFree    (var Buf: GlobBuffer); attribute (name
       = '_p_GlobFree'); external;
     
     type
       TPasswordEntry = record
         UserName, RealName, Password, HomeDirectory, Shell: PString;
         UID, GID: Integer
       end;
     
       PPasswordEntries = ^TPasswordEntries;
       TPasswordEntries (Count: Integer) = array [1 .. Max (1, Count)] of
       TPasswordEntry;
     
     { Finds a password entry by user name. Returns True if found, False
       otherwise. }
     function  GetPasswordEntryByName (const UserName: String; var Entry:
       TPasswordEntry): Boolean; attribute (name
       = '_p_GetPasswordEntryByName'); external;
     
     { Finds a password entry by UID. Returns True if found, False
       otherwise. }
     function  GetPasswordEntryByUID  (UID: Integer; var Entry:
       TPasswordEntry): Boolean; attribute (name
       = '_p_GetPasswordEntryByUID'); external;
     
     { Returns all password entries, or nil if none found. }
     function  GetPasswordEntries: PPasswordEntries; attribute (name
       = '_p_GetPasswordEntries'); external;
     
     { Dispose of a TPasswordEntry. }
     procedure DisposePasswordEntry (Entry: TPasswordEntry); attribute
       (name = '_p_DisposePasswordEntry'); external;
     
     { Dispose of a PPasswordEntries. }
     procedure DisposePasswordEntries (Entries: PPasswordEntries);
       attribute (name = '_p_DisposePasswordEntries'); external;
     
     { Returns the mount point (Unix) or drive (Dos) which is part of the
       given path. If the path does not contain any (i.e., is a relative
       path), an empty string is returned. Therefore, if you want to get
       the mount point or drive in any case, apply FExpand or
       RealPath to the argument. }
     function  GetMountPoint (const Path: String): TString; attribute
       (name = '_p_GetMountPoint'); external;
     
     type
       TSystemInfo = record
         OSName,
         OSRelease,
         OSVersion,
         MachineType,
         HostName,
         DomainName: TString
       end;
     
     { Returns system information if available. Fields not available will
       be empty. }
     function  SystemInfo: TSystemInfo; attribute (name
       = '_p_SystemInfo'); external;
     
     { Returns the path to the shell (as the result) and the option that
       makes it execute the command specified in the following argument
       (in Option). Usually these are the environment value of
       ShellEnvVar, and ShellExecCommand, but on Dos systems, the
       function will first try UnixShellEnvVar, and UnixShellExecCommand
       because ShellEnvVar will usually point to command.com, but
       UnixShellEnvVar can point to bash which is usually a better choice
       when present. If UnixShellEnvVar is not set, or the shell given
       does not exist, it will use ShellEnvVar, and ShellExecCommand.
       Option may be Null (in case you want to invoke the shell
       interactively). }
     function  GetShellPath (var Option: String): TString; attribute
       (name = '_p_GetShellPath'); external;
     
     { Returns the path of the running executable. *Note*: On most
       systems, this is *not* guaranteed to be the full path, but often
       just the same as ParamStr (0) which usually is the name given on
       the command line. Only on some systems with special support, it
       returns the full path when ParamStr (0) doesn't. }
     function  ExecutablePath: TString; attribute (name
       = '_p_ExecutablePath'); external;
     
     { Returns a file name suitable for a global (system-wide) or local
       (user-specific) configuration file, depending on the Global
       parameter. The function does not guarantee that the file name
       returned exists or is readable or writable.
     
       In the following table, the base name <base> is given with the
       BaseName parameter. If it is empty, the base name is the name of
       the running program (as returned by ExecutablePath, without
       directory and extension. <prefix> (Unix only) stands for the
       value of the Prefix parameter (usual values include '', '/usr' and
       '/usr/local'). <dir> (Dos only) stands for the directory where
       the running program resides. $foo stands for the value of the
       environment variable foo.
     
               Global                    Local
       Unix:   <prefix>/etc/<base>.conf  $HOME/.<base>
     
       DJGPP:  $DJDIR\etc\<base>.ini     $HOME\<base>.cfg
               <dir>\<base>.ini          <dir>\<base>.cfg
     
       Other   $HOME\<base>.ini          $HOME\<base>.cfg
         Dos:  <dir>\<base>.ini          <dir>\<base>.cfg
     
       As you see, there are two possibilities under Dos. If the first
       file exists, it is returned. Otherwise, if the second file exists,
       that is returned. If none of them exists (but the program might
       want to create a file), if the environment variable (DJDIR or
       HOME, respectively) is set, the first file name is returned,
       otherwise the second one. This rather complicated scheme should
       give the most reasonable results for systems with or without DJGPP
       installed, and with or without already existing config files. Note
       that DJDIR is always set on systems with DJGPP installed, while
       HOME is not. However, it is easy for users to set it if they want
       their config files in a certain directory rather than with the
       executables. }
     function  ConfigFileName (const Prefix, BaseName: String; Global:
       Boolean): TString; attribute (name = '_p_ConfigFileName');
       external;
     
     { Returns a directory name suitable for global, machine-independent
       data. The function garantees that the name returned ends with a
       DirSeparator, but does not guarantee that it exists or is
       readable or writable.
     
       Note: If the prefix is empty, it is assumed to be '/usr'. (If you
       really want /share, you could pass '/' as the prefix, but that's
       very uncommon.)
     
       Unix:   <prefix>/share/<base>/
     
       DJGPP:  $DJDIR\share\<base>\
               <dir>\
     
       Other   $HOME\<base>\
         Dos:  <dir>\
     
       About the symbols used above, and the two possibilities under Dos,
       see the comments for ConfigFileName. }
     function  DataDirectoryName (const Prefix, BaseName: String):
       TString; attribute (name = '_p_DataDirectoryName'); external;
     
     { Executes a command line. Reports execution errors via the IOResult
       mechanism and returns the exit status of the executed program.
       Execute calls RestoreTerminal with the argument True before and
       False after executing the process, ExecuteNoTerminal does not. }
     function  Execute (const CmdLine: String): Integer; attribute
       (iocritical, name = '_p_Execute'); external;
     function  ExecuteNoTerminal (const CmdLine: String): Integer;
       attribute (iocritical, name = '_p_ExecuteNoTerminal'); external;
     
     { File handling routines, from files.pas }
     
     type
       Natural = 1 .. MaxInt;
       IOSelectEvents = (SelectReadOrEOF, SelectRead, SelectEOF,
       SelectWrite, SelectException, SelectAlways);
     
     const
       IOSelectEventMin = Low (IOSelectEvents);
       IOSelectEventMax = Pred (SelectAlways);
     
     type
       IOSelectType = record
         f: PAnyFile;
         Wanted: set of IOSelectEvents;
         Occurred: set of IOSelectEventMin .. IOSelectEventMax
       end;
     
     { Waits for one of several events to happen. Returns when one or
       more of the wanted events for one of the files occur. If they have
       already occurred before calling the function, it returns
       immediately. MicroSeconds can specify a timeout. If it is 0, the
       function will return immediately, whether or not an event has
       occurred. If it is negative, the function will wait forever until
       an event occurs. The Events parameter can be Null, in which case
       the function only waits for the timeout. If any of the file
       pointers (f) in Events are nil or the files pointed to are closed,
       they are simply ignored for convenience.
     
       It returns the index of one of the files for which any event has
       occurred. If events have occurred for several files, is it
       undefined which of these file's index is returned. If no event
       occurs until the timeout, 0 is returned. If an error occurs or the
       target system does not have a select() system call and Events is
       not Null, a negative value is returned. In the Occurred field of
       the elements of Events, events that have occurred are set. The
       state of events not wanted is undefined.
     
       The possible events are:
       SelectReadOrEOF: the file is at EOF or data can be read now.
       SelectRead:      data can be read now.
       SelectEOF:       the file is at EOF.
       SelectWrite:     data can be written now.
       SelectException: an exception occurred on the file.
       SelectAlways:    if this is set, *all* requested events will be
                        checked for this file in any case. Otherwise,
                        checks may be skipped if already another event
                        for this or another file was found.
     
       Notes:
       Checking for EOF requires some reading ahead internally (just like
       the EOF function) which can be avoided by setting SelectReadOrEOF
       instead of SelectRead and SelectEOF. If this is followed by, e.g.,
       a BlockRead with 4 parameters, the last parameter will be 0 if and
       only the file is at EOF, and otherwise, data will be read directly
       from the file without reading ahead and buffering.
     
       SelectAlways should be set for files for which events are
       considered to be of higher priority than others. Otherwise, if one
       is interested in just any event, not setting SelectAlways may be a
       little faster. }
     function  IOSelect (var Events: array [m .. n: Natural] of
       IOSelectType; MicroSeconds: MicroSecondTimeType): Integer;
       attribute (name = '_p_IOSelect'); external;
     
     { A simpler interface to SelectIO for the most common use. Waits for
       SelectReadOrEOF on all files and returns an index. }
     function  IOSelectRead (const Files: array [m .. n: Natural] of
       PAnyFile; MicroSeconds: MicroSecondTimeType): Integer; attribute
       (name = '_p_IOSelectRead'); external;
     
     { Bind a filename to an external file }
     procedure AssignFile   (var t: AnyFile; const FileName: String);
       attribute (name = '_p_AssignFile'); external;
     procedure AssignBinary (var t: Text; const FileName: String);
       attribute (name = '_p_AssignBinary'); external;
     procedure AssignHandle (var t: AnyFile; Handle: Integer; CloseFlag:
       Boolean); attribute (name = '_p_AssignHandle'); external;
     
     { Under development }
     procedure AnyStringTFDD_Reset (var f: AnyFile; var Buf:
       ConstAnyString); attribute (name = '_p_AnyStringTFDD_Reset');
       external;
     { @@ procedure AnyStringTFDD_Rewrite (var f: AnyFile; var Buf:
       VarAnyString); attribute (name = '_p_AnyStringTFDD_Rewrite'); }
     procedure StringTFDD_Reset (var f: AnyFile; var Buf: ConstAnyString;
       const s: String); attribute (name = '_p_StringTFDD_Reset');
       external;
     { @@ procedure StringTFDD_Rewrite (var f: AnyFile; var Buf:
       VarAnyString; var s: String); attribute (name
       = '_p_StringTFDD_Rewrite'); }
     
     { Returns True is a terminal device is open on the file f, False if
       f is not open or not connected to a terminal. }
     function  IsTerminal (protected var f: AnyFile): Boolean; attribute
       (name = '_p_IsTerminal'); external;
     
     { Returns the file name of the terminal device that is open on the
       file f. Returns the empty string if (and only if) f is not open or
       not connected to a terminal. }
     function  GetTerminalName (protected var f: AnyFile): TString;
       attribute (name = '_p_GetTerminalName'); external;
     
     { Command line option parsing, from getopt.pas }
     
     const
       EndOfOptions      = #255;
       NoOption          = #1;
       UnknownOption     = '?';
       LongOption        = #0;
       UnknownLongOption = '?';
     
     var
       FirstNonOption        : Integer; attribute (name
       = '_p_FirstNonOption'); external;
       HasOptionArgument     : Boolean; attribute (name
       = '_p_HasOptionArgument'); external;
       OptionArgument        : TString; attribute (name
       = '_p_OptionArgument'); external;
       UnknownOptionCharacter: Char; attribute (name
       = '_p_UnknownOptionCharacter'); external;
       GetOptErrorFlag       : Boolean; attribute (name
       = '_p_GetOptErrorFlag'); external;
     
     { Parses command line arguments for options and returns the next
       one.
     
       If a command line argument starts with -, and is not exactly -
       or --, then it is an option element. The characters of this
       element (aside from the initial -) are option characters. If
       GetOpt is called repeatedly, it returns successively each of the
       option characters from each of the option elements.
     
       If GetOpt finds another option character, it returns that
       character, updating FirstNonOption and internal variables so
       that the next call to GetOpt can resume the scan with the
       following option character or command line argument.
     
       If there are no more option characters, GetOpt returns
       EndOfOptions. Then FirstNonOption is the index of the first
       command line argument that is not an option. (The command line
       arguments have been permuted so that those that are not options
       now come last.)
     
       OptString must be of the form [+|-]abcd:e:f:g::h::i::.
     
       a, b, c are options without arguments
       d, e, f are options with required arguments
       g, h, i are options with optional arguments
     
       Arguments are text following the option character in the same
       command line argument, or the text of the following command line
       argument. They are returned in OptionArgument. If an option has no
       argument, OptionArgument is empty. The variable HasOptionArgument
       tells whether an option has an argument. This is mostly useful for
       options with optional arguments, if one wants to distinguish an
       empty argument from no argument.
     
       If the first character of OptString is +, GetOpt stops at the
       first non-option argument.
     
       If it is -, GetOpt treats non-option arguments as options and
       return NoOption for them.
     
       Otherwise, GetOpt permutes arguments and handles all options,
       leaving all non-options at the end. However, if the environment
       variable POSIXLY_CORRECT is set, the default behaviour is to stop
       at the first non-option argument, as with +.
     
       The special argument -- forces an end of option-scanning
       regardless of the first character of OptString. In the case of
       -, only -- can cause GetOpt to return EndOfOptions with
       FirstNonOption <= ParamCount.
     
       If an option character is seen that is not listed in OptString,
       UnknownOption is returned. The unrecognized option character is
       stored in UnknownOptionCharacter. Unless GetOptErrorFlag is set to
       False, an error message is printed to StdErr automatically. }
     function  GetOpt (const OptString: String): Char; attribute (name
       = '_p_GetOpt'); external;
     
     type
       OptArgType = (NoArgument, RequiredArgument, OptionalArgument);
     
       OptionType = record
         OptionName: CString;
         Argument  : OptArgType;
         Flag      : ^Char;  { if nil, v is returned. Otherwise, Flag^ is
       ... }
         v         : Char    { ... set to v, and LongOption is returned }
       end;
     
     { Recognize short options, described by OptString as above, and long
       options, described by LongOptions.
     
       Long-named options begin with -- instead of -. Their names may
       be abbreviated as long as the abbreviation is unique or is an
       exact match for some defined option. If they have an argument, it
       follows the option name in the same argument, separated from the
       option name by a =, or else the in next argument. When GetOpt
       finds a long-named option, it returns LongOption if that option's
       Flag field is non-nil, and the value of the option's v field
       if the Flag field is nil.
     
       LongIndex, if not Null, returns the index in LongOptions of the
       long-named option found. It is only valid when a long-named option
       has been found by the most recent call.
     
       If LongOnly is set, - as well as -- can indicate a long
       option. If an option that starts with - (not --) doesn't match
       a long option, but does match a short option, it is parsed as a
       short option instead. If an argument has the form -f, where f is
       a valid short option, don't consider it an abbreviated form of a
       long option that starts with f. Otherwise there would be no way
       to give the -f short option. On the other hand, if there's a
       long option fubar and the argument is -fu, do consider that an
       abbreviation of the long option, just like --fu, and not -f
       with argument u. This distinction seems to be the most useful
       approach.
     
       As an additional feature (not present in the C counterpart), if
       the last character of OptString is - (after a possible starting
       + or - character), or OptString is empty, all long options
       with a nil Flag field will automatically be recognized as short
       options with the character given by the v field. This means, in
       the common (and recommended) case that all short options have long
       equivalents, you can simply pass an empty OptString (or pass +-
       or -- as OptString if you want this behaviour, see the comment
       for GetOpt), and you will only have to maintain the LongOptions
       array when you add or change options. }
     function  GetOptLong (const OptString: String; const LongOptions:
       array [m .. n: Integer] of OptionType { can be Null };
                           var LongIndex: Integer { can be Null };
       LongOnly: Boolean): Char; attribute (name = '_p_GetOptLong');
       external;
     
     { Reset GetOpt's state and make the next GetOpt or GetOptLong start
       (again) with the StartArgument'th argument (may be 1). This is
       useful for special purposes only. It is *necessary* to do this
       after altering the contents of CParamCount/CParameters (which is
       not usually done, either). }
     procedure ResetGetOpt (StartArgument: Integer); attribute (name
       = '_p_ResetGetOpt'); external;
     
     { Set operations, from sets.pas }
     
     { All set operations are built-in identifiers and not declared in
       gpc.pas. }
     
     { Heap management routines, from heap.pas }
     
     { GPC implements both Mark/Release and Dispose. Both can be mixed
       freely in the same program. Dispose should be preferred, since
       it's faster. }
     
     { C heap management routines. NOTE: if Release is used anywhere in
       the program, CFreeMem and CReAllocMem may not be used for pointers
       that were not allocated with CGetMem. }
     function  CGetMem     (Size: SizeType): Pointer; external
       name 'malloc';
     procedure CFreeMem    (aPointer: Pointer); external name 'free';
     function  CReAllocMem (aPointer: Pointer; NewSize: SizeType):
       Pointer; external name 'realloc';
     
     type
       GetMemType     = ^function (Size: SizeType): Pointer;
       FreeMemType    = ^procedure (aPointer: Pointer);
       ReAllocMemType = ^function (aPointer: Pointer; NewSize: SizeType):
       Pointer;
     
     { These variables can be set to user-defined routines for memory
       allocation/deallocation. GetMemPtr may return nil when
       insufficient memory is available. GetMem/New will produce a
       runtime error then. }
     var
       GetMemPtr    : GetMemType; attribute (name = '_p_GetMemPtr');
       external;
       FreeMemPtr   : FreeMemType; attribute (name = '_p_FreeMemPtr');
       external;
       ReAllocMemPtr: ReAllocMemType; attribute (name
       = '_p_ReAllocMemPtr'); external;
     
       { Address of the lowest byte of heap used }
       HeapLow: PtrCard; attribute (name = '_p_HeapLow'); external;
     
       { Address of the highest byte of heap used }
       HeapHigh: PtrCard; attribute (name = '_p_HeapHigh'); external;
     
       { If set to true, Dispose etc. will raise a runtime error if
         given an invalid pointer. }
       HeapChecking: Boolean; attribute (name = '_p_HeapChecking');
       external;
     
     const
       UndocumentedReturnNil = Pointer (-1);
     
     function  SuspendMark: Pointer; attribute (name = '_p_SuspendMark');
       external;
     procedure ResumeMark (p: Pointer); attribute (name
       = '_p_ResumeMark'); external;
     
     { Calls the procedure Proc for each block that would be released
       with Release (aMark). aMark must have been marked with Mark. For
       an example of its usage, see the HeapMon unit. }
     procedure ForEachMarkedBlock (aMark: Pointer; procedure Proc
       (aPointer: Pointer; aSize: SizeType; aCaller: Pointer)); attribute
       (name = '_p_ForEachMarkedBlock'); external;
     
     procedure ReAllocMem (var aPointer: Pointer; NewSize: SizeType);
       attribute (name = '_p_ReAllocMem'); external;
     
     { Memory transfer procedures, from move.pas }
     
     { The move operations are built-in identifiers and not declared in
       gpc.pas. }
     
     { Routines to handle endianness, from endian.pas }
     
     { Boolean constants about endianness and alignment }
     
     const
       BitsBigEndian  = {$ifdef __BITS_LITTLE_ENDIAN__}
                        False
                        {$elif defined (__BITS_BIG_ENDIAN__)}
                        True
                        {$else}
                        {$error Bit endianness is not defined!}
                        {$endif};
     
       BytesBigEndian = {$ifdef __BYTES_LITTLE_ENDIAN__}
                        False
                        {$elif defined (__BYTES_BIG_ENDIAN__)}
                        True
                        {$else}
                        {$error Byte endianness is not defined!}
                        {$endif};
     
       WordsBigEndian = {$ifdef __WORDS_LITTLE_ENDIAN__}
                        False
                        {$elif defined (__WORDS_BIG_ENDIAN__)}
                        True
                        {$else}
                        {$error Word endianness is not defined!}
                        {$endif};
     
       NeedAlignment  = {$ifdef __NEED_ALIGNMENT__}
                        True
                        {$elif defined (__NEED_NO_ALIGNMENT__)}
                        False
                        {$else}
                        {$error Alignment is not defined!}
                        {$endif};
     
     { Convert single variables from or to little or big endian format.
       This only works for a single variable or a plain array of a simple
       type. For more complicated structures, this has to be done for
       each component separately! Currently, ConvertFromFooEndian and
       ConvertToFooEndian are the same, but this might not be the case on
       middle-endian machines. Therefore, we provide different names. }
     procedure ReverseBytes            (var Buf; ElementSize, Count:
       SizeType); attribute (name = '_p_ReverseBytes'); external;
     procedure ConvertFromLittleEndian (var Buf; ElementSize, Count:
       SizeType); attribute (name = '_p_ConvertLittleEndian'); external;
     procedure ConvertFromBigEndian    (var Buf; ElementSize, Count:
       SizeType); attribute (name = '_p_ConvertBigEndian'); external;
     procedure ConvertToLittleEndian   (var Buf; ElementSize, Count:
       SizeType); external name '_p_ConvertLittleEndian';
     procedure ConvertToBigEndian      (var Buf; ElementSize, Count:
       SizeType); external name '_p_ConvertBigEndian';
     
     { Read a block from a file and convert it from little or
       big endian format. This only works for a single variable or a
       plain array of a simple type, note the comment for
       ConvertFromLittleEndian and ConvertFromBigEndian. }
     procedure BlockReadLittleEndian   (var aFile: File; var   Buf;
       ElementSize, Count: SizeType); attribute (iocritical, name
       = '_p_BlockRead_LittleEndian'); external;
     procedure BlockReadBigEndian      (var aFile: File; var   Buf;
       ElementSize, Count: SizeType); attribute (iocritical, name
       = '_p_BlockRead_BigEndian'); external;
     
     { Write a block variable to a file and convert it to little or big
       endian format before. This only works for a single variable or a
       plain array of a simple type. Apart from this, note the comment
       for ConvertToLittleEndian and ConvertToBigEndian. }
     procedure BlockWriteLittleEndian  (var aFile: File; const Buf;
       ElementSize, Count: SizeType); attribute (iocritical, name
       = '_p_BlockWrite_LittleEndian'); external;
     procedure BlockWriteBigEndian     (var aFile: File; const Buf;
       ElementSize, Count: SizeType); attribute (iocritical, name
       = '_p_BlockWrite_BigEndian'); external;
     
     { Read and write strings from/to binary files, where the length is
       stored in the given endianness and with a fixed size (64 bits),
       and therefore is independent of the system. }
     procedure ReadStringLittleEndian  (var f: File; var s: String);
       attribute (iocritical, name = '_p_ReadStringLittleEndian');
       external;
     procedure ReadStringBigEndian     (var f: File; var s: String);
       attribute (iocritical, name = '_p_ReadStringBigEndian'); external;
     procedure WriteStringLittleEndian (var f: File; const s: String);
       attribute (iocritical, name = '_p_WriteStringLittleEndian');
       external;
     procedure WriteStringBigEndian    (var f: File; const s: String);
       attribute (iocritical, name = '_p_WriteStringBigEndian');
       external;
     
     { Initialization, from init.pas }
     
     var
       InitProc: ^procedure; attribute (name = '_p_InitProc'); external;

Node: GPC Units, Previous: Run Time System, Up: Programming

6.15 Units included with GPC

GPC distributions now include a number of useful Pascal units and a complete set of BP compatibility units - except for the Graph unit (which is currently distributed separately due to its license) and the OOP stuff. The main use of these units is to provide a way to port BP programs to GPC as easily as possible. Some of the units also implement functionaliy not available otherwise.

Most of the BP compatibility units - except CRT and Printer - are merely meant to let programs written for BP compile with GPC as easily as possible. They should not be used in newly written code, and for code ported from BP to GPC, it is suggested to replace them successively with the more powerful - and often easier to use - alternatives that GPC's Run Time System (see Run Time System) offers.

The following sections describe all units included with GPC (besides the GPC module which describes the interface to the Run Time System, Run Time System).

Node: CRT, Next: , Up: GPC Units

6.15.1 BP compatibility: CRT & WinCRT, portable, with many extensions

The following listing contains the interface of the CRT unit.

CRT is a curses based unit for text screen handling. It is compatible to BP's CRT unit, even in a lot of minor details like the values of function key codes and includes some routines for compatibility with TP5's Win unit as well as BP's WinCRT and Turbo Power's TPCrt units, and some extensions.

The unit has been extended by many functions that were lacking in BP's unit and required assembler code or direct memory/port access to be implemented under BP. The GPC version is now fully suited for portable, real-world programming without any dirty tricks.

The unit is also available as WinCRT, completely identical to CRT. The only purpose of this "feature" is to let programs written for TPW or BP, with a uses WinCRT directive, compile without changes. Unlike TPW/BP's WinCRT unit, GPC's unit is not crippled, compared to CRT.

To use this unit, you will need the ncurses (version 5.0 or newer) or PDCurses library which can be found in http://www.gnu-pascal.de/libs/. 

     { CRT (Crt Replacement Tool)
       Portable BP compatible CRT unit for GPC with many extensions
     
       This unit is aware of terminal types. This means programs using
       this unit will work whether run locally or while being logged in
       remotely from a system with a completely different terminal type
       (as long as the appropriate terminfo entry is present on the
       system where the program is run).
     
       NOTES:
     
       - The CRT unit needs the ncurses and panel libraries which should
         be available for almost any system. For Dos systems, where
         ncurses is not available, it is configured to use the PDCurses
         and its panel library instead. On Unix systems with X11, it can
         also use PDCurses (xcurses) and xpanel to produce X11 programs.
         The advantage is that the program won't need an xterm with a
         valid terminfo entry, the output may look a little nicer and
         function keys work better than in an xterm, but the disadvantage
         is that it will only run under X. The ncurses and PDCurses
         libraries (including panel and xpanel, resp.) can be found in
         http://www.gnu-pascal.de/libs/
         (Note that ncurses is already installed on many Unix systems.)
         For ncurses, version 5.0 or newer is strongly recommended
         because older versions contain a bug that severely affects CRT
         programs.
     
         When an X11 version under Unix is wanted, give -DX11 when
         compiling crt.pas and crtc.c (or when compiling crt.pas or a
         program that uses CRT with --automake). On pre-X11R6 systems,
         give -DNOX11R6 additionally. You might also have to give the
         path to the X11 libraries with -L, e.g. -L /usr/X11/lib.
     
       - A few features cannot be implemented in a portable way and are
         only available on some systems:
     
           Sound, NoSound 1)                  -----------------------.
           GetShiftState                      ------------------.    |
           TextMode etc. 2)                   -------------.    |    |
           CRTSavePreviousScreen              --------.    |    |    |
           Interrupt signal (Ctrl-C) handling ---.    |    |    |    |
                                                 |    |    |    |    |
         Linux/IA32 3) (terminal)                X    X 4) X 5) X 6) X 6)
         Other Unix (terminal)                   X    X 7) X 5) -    -
         Unix (X11 version)                      X    X    -    X    -
         Dos (DJGPP)                             X    X    X    X    X
         MS-Windows (Cygwin, mingw, MSYS)        X    -    X 8) X    -
     
         Notes:
     
         1) If you define NO_CRT_DUMMY_SOUND while compiling CRT, you
            will get linking errors when your program tries to use
            Sound/NoSound on a platform where it's not supported (which
            is useful to detect at compile time if playing sound is a
            major task of your program). Otherwise, Sound/NoSound will
            simply do nothing (which is usually acceptable if the program
            uses these routines just for an occasional beep).
     
         2) Changing to monochrome modes works on all platforms. Changing
            the screen size only works on those indicated. However, even
            on the platforms not supported, the program will react to
            screen size changes by external means (e.g. changing the
            window size with the mouse if running in a GUI window or
            resizing a console or virtual terminal).
     
         3) Probably also on other processors, but I've had no chance to
            test this yet.
     
         4) Only on a local console with access permissions to the
            corresponding virtual console memory device or using the
            crtscreen utility (see crtscreen.c in the demos directory).
     
         5) Only if supported by an external command (e.g., in xterms and
            on local Linux consoles). The command to be called can be
            defined in the environment variable RESIZETERM (where the
            variables columns and lines in the command are set to the
            size wanted). If not set, the code will try resize -s in an
            xterm and otherwise SVGATextMode and setfont. For this to
            work, these utilities need to be present in the PATH or
            /usr/sbin or /usr/local/sbin. Furthermore, SVGATextMode
            and setfont require root permissions, either to the
            executable of the program compiled with CRT or to resizecons
            (called by setfont) or SVGATextMode. To allow the latter, do
            "chmod u+s `which resizecons`" and/or
            "chmod u+s `which SVGATextMode`", as root once, but only if
            you really want each user to be allowed to change the text
            mode.
     
         6) Only on local consoles.
     
         7) Some terminals only. Most xterms etc. support it as well as
            other terminals that support an "alternate screen" in the
            smcup/rmcup terminal capabilities.
     
         8) Only with PDCurses, not with ncurses. Changing the number of
            screen *columns* doesn't work in a full-screen session.
     
       - When CRT is initialized (automatically or explicitly; see the
         comments for CRTInit), the screen is cleared, and at the end of
         the program, the cursor is placed at the bottom of the screen
         (curses behaviour).
     
       - All the other things (including most details like color and
         function key constants) are compatible with BP's CRT unit, and
         there are many extensions that BP's unit does not have.
     
       - When the screen size is changed by an external event (e.g.,
         resizing an xterm or changing the screen size from another VC
         under Linux), the virtual "function key" kbScreenSizeChanged is
         returned. Applications can use the virtual key to resize their
         windows. kbScreenSizeChanged will not be returned if the screen
         size change was initiated by the program itself (by using
         TextMode or SetScreenSize). Note that TextMode sets the current
         panel to the full screen size, sets the text attribute to the
         default and clears the window (BP compatibility), while
         SetScreenSize does not.
     
       - After the screen size has been changed, whether by using
         TextMode, SetScreenSize or by an external event, ScreenSize will
         return the new screen size. The current window and all panels
         will have been adjusted to the new screen size. This means, if
         their right or lower ends are outside the new screen size, the
         windows are moved to the left and/or top as far as necessary. If
         this is not enough, i.e., if they are wider/higher than the new
         screen size, they are shrinked to the total screen width/height.
         When the screen size is enlarged, window sizes are not changed,
         with one exception: Windows that extend through the whole screen
         width/height are enlarged to the whole new screen width/height
         (in particular, full-screen windows remain full-screen). This
         behaviour might not be optimal for all purposes, but you can
         always resize your windows in your application after the screen
         size change.
     
       - (ncurses only) The environment variable ESCDELAY specifies the
         number of milliseconds allowed between an Esc character and
         the rest of an escape sequence (default 1000). Setting it to a
         value too small can cause problems with programs not recognizing
         escape sequences such as function keys, especially over slow
         network connections. Setting it to a value too large can delay
         the recognition of an ESC key press notably. On local Linux
         consoles, e.g., 10 seems to be a good value.
     
       - When trying to write portable programs, don't rely on exactly
         the same look of your output and the availability of all the key
         combinations. Some kinds of terminals support only some of the
         display attributes and special characters, and usually not all
         of the keys declared are really available. Therefore, it's safer
         to provide the same function on different key combinations and
         to not use the more exotic ones.
     
       - CRT supports an additional modifier key (if present), called
         Extra. On DJGPP, it's the <Scroll Lock> key, under X11 it's
         the modifier #4, and on a local Linux console, it's the CtrlL
         modifier (value 64) which is unused on many keytabs and can be
         mapped to any key(s), e.g. to those keys on new keyboards with
         these ugly symbols waiting to be replaced by penguins (keycodes
         125 and 127) by inserting the following two lines into your
         /etc/default.keytab and reloading the keytab with loadkeys
         (you usually have to do this as root):
     
         keycode 125 = CtrlL
         keycode 127 = CtrlL
     
       Copyright (C) 1998-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License.
     
       Please also note the license of the curses library used. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030722}
     {$error This unit requires GPC release 20030722 or newer.}
     {$endif}
     
     unit {$ifdef THIS_IS_WINCRT} WinCRT {$else} CRT {$endif};
     
     interface
     
     uses GPC;
     
     const
       { CRT modes }
       BW40          = 0;            { 40x25 Black/White }
       CO40          = 1;            { 40x25 Color }
       BW80          = 2;            { 80x25 Black/White }
       CO80          = 3;            { 80x25 Color }
       Mono          = 7;            { 80x25 Black/White }
       Font8x8       = 256;          { Add-in for 80x43 or 80x50 mode }
     
       { Mode constants for Turbo Pascal 3.0 compatibility }
       C40           = CO40;
       C80           = CO80;
     
       { Foreground and background color constants }
       Black         = 0;
       Blue          = 1;
       Green         = 2;
       Cyan          = 3;
       Red           = 4;
       Magenta       = 5;
       Brown         = 6;
       LightGray     = 7;
     
       { Foreground color constants }
       DarkGray      = 8;
       LightBlue     = 9;
       LightGreen    = 10;
       LightCyan     = 11;
       LightRed      = 12;
       LightMagenta  = 13;
       Yellow        = 14;
       White         = 15;
     
       { Add-in for blinking }
       Blink         = 128;
     
     type
       TTextAttr = Byte;
     
     var
       { If False (default: True), catch interrupt signals (SIGINT;
         Ctrl-C), and other flow control characters as well as SIGTERM,
         SIGHUP and perhaps other signals }
       CheckBreak: Boolean = True; attribute (name = 'crt_CheckBreak');
     
       { If True (default : False), replace Ctrl-Z by #0 in input }
       CheckEOF: Boolean = False; attribute (name = 'crt_CheckEOF');
     
       { Ignored -- meaningless here }
       DirectVideo: Boolean = True;
     
       { Ignored -- curses or the terminal driver will take care of that
         when necessary }
       CheckSnow: Boolean = False;
     
       { Current (sic!) text mode }
       LastMode: Word = 3; attribute (name = 'crt_LastMode');
     
       { Current text attribute }
       TextAttr: TTextAttr = 7; attribute (name = 'crt_TextAttr');
     
       { Window upper left coordinates. *Obsolete*! Please see WindowMin
         below. }
       WindMin: Word = not Word (0); attribute (name = 'crt_WindMin');
     
       { Window lower right coordinates. *Obsolete*! Please see WindowMax
         below. }
       WindMax: Word = not Word (0); attribute (name = 'crt_WindMax');
     
     procedure AssignCRT (var f: Text);
     function  KeyPressed: Boolean; external name 'crt_KeyPressed';
     function  ReadKey: Char; external name 'crt_ReadKey';
     
     { Not effective on all platforms, see above. See also SetScreenSize
       and SetMonochrome. }
     procedure TextMode (Mode: Integer);
     
     procedure Window (x1, y1, x2, y2: Integer); external
       name 'crt_Window';
     procedure GotoXY (x, y: Integer); external name 'crt_GotoXY';
     function  WhereX: Integer; external name 'crt_WhereX';
     function  WhereY: Integer; external name 'crt_WhereY';
     procedure ClrScr; external name 'crt_ClrScr';
     procedure ClrEOL; external name 'crt_ClrEOL';
     procedure InsLine; external name 'crt_InsLine';
     procedure DelLine; external name 'crt_DelLine';
     procedure TextColor (Color: TTextAttr);
     procedure TextBackground (Color: TTextAttr);
     procedure LowVideo;
     procedure HighVideo;
     procedure NormVideo;
     procedure Delay (MS: Word); external name 'crt_Delay';
     
     { Not available on all platforms, see above }
     procedure Sound (Hz: Word); external name 'crt_Sound';
     procedure NoSound; external name 'crt_NoSound';
     
     { =================== Extensions over BP's CRT =================== }
     
     { Initializes the CRT unit. Should be called before using any of
       CRT's routines.
     
       Note: For BP compatibility, CRT is initizalized automatically when
       (almost) any of its routines are used for the first time. In this
       case, some defaults are set to match BP more closely. In
       particular, the PC charset (see SetPCCharSet) is enabled then
       (disabled otherwise), and the update level (see SetCRTUpdate) is
       set to UpdateRegularly (UpdateWaitInput otherwise). This feature
       is meant for BP compatibility *only*. Don't rely on it when
       writing a new program. Use CRTInit then, and set the defaults to
       the values you want explicitly.
     
       SetCRTUpdate is one of those few routines which will not cause CRT
       to be initialized immediately, and a value set with it will
       survive both automatic and explicit initialization, so you can use
       it to set the update level without caring which way CRT will be
       initialized. (This does not apply to SetPCCharSet. Since it works
       on a per-panel basis, it has to initialize CRT first, so there is
       a panel to start with.)
     
       If you terminate the program before calling CRTInit or any routine
       that causes automatic initialization, curses will never be
       initialized, so e.g., the screen won't be cleared. This can be
       useful, e.g., to check the command line arguments (or anything
       else) and if there's a problem, write an error and abort. Just be
       sure to write the error to StdErr, not Output (because Output will
       be assigned to CRT, and therefore writing to Output will cause CRT
       to be initialized, and because errors belong to StdErr, anyway),
       and to call RestoreTerminal (True) before (just to be sure, in
       case some code -- perhaps added later, or hidden in the
       initialization of some unit -- does initialize CRT). }
     procedure CRTInit; external name 'crt_Init';
     
     { Changes the input and output file and the terminal description CRT
       uses. Only effective with ncurses, and only if called before CRT
       is initialized (automatically or explicitly; see the comments for
       CRTInit). If TerminalType is nil, the default will be used. If
       InputFile and/or OutputFile are Null, they remain unchanged. }
     procedure CRTSetTerminal (TerminalType: CString; var InputFile,
       OutputFile: AnyFile); attribute (name = 'crt_SetTerminal');
     
     { If called with an argument True, it causes CRT to save the
       previous screen contents if possible (see the comments at the
       beginning of the unit), and restore them when calling
       RestoreTerminal (True). After RestoreTerminal (False), they're
       saved again, and at the end of the program, they're restored. If
       called with an argument False, it will prohibit this behaviour.
       The default, if this procedure is not called, depends on the
       terminal (generally it is active on most xterms and similar and
       not active on most other terminals).
     
       This procedure should be called before initializing CRT (using
       CRTInit or automatically), otherwise the previous screen contents
       may already have been overwritten. It has no effect under XCurses,
       because the program uses its own window, anyway. }
     procedure CRTSavePreviousScreen (On: Boolean); external
       name 'crt_SavePreviousScreen';
     
     { Returns True if CRTSavePreviousScreen was called with argument
       True and the functionality is really available. Note that the
       result is not reliable until CRT is initialized, while
       CRTSavePreviousScreen should be called before CRT is initialized.
       That's why they are two separate routines. }
     function  CRTSavePreviousScreenWorks: Boolean; external
       name 'crt_SavePreviousScreenWorks';
     
     { If CRT is initialized automatically, not via CRTInit, and
       CRTAutoInitProc is not nil, it will be called before actually
       initializing CRT. }
     var
       CRTAutoInitProc: procedure = nil; attribute (name
       = 'crt_AutoInitProc');
     
     { Aborts with a runtime error saying that CRT was not initialized.
       If you set CRTAutoInitProc to this procedure, you can effectively
       disable CRT's automatic initialization. }
     procedure CRTNotInitialized; attribute (name
       = 'crt_NotInitialized');
     
     { Set terminal to shell or curses mode. An internal procedure
       registered by CRT via RegisterRestoreTerminal does this as well,
       so CRTSetCursesMode has to be called only in unusual situations,
       e.g. after executing a process that changes terminal modes, but
       does not restore them (e.g. because it crashed or was killed), and
       the process was not executed with the Execute routine, and
       RestoreTerminal was not called otherwise. If you set it to False
       temporarily, be sure to set it back to True before doing any
       further CRT operations, otherwise the result may be strange. }
     procedure CRTSetCursesMode (On: Boolean); external
       name 'crt_SetCursesMode';
     
     { Do the same as RestoreTerminal (True), but also clear the screen
       after restoring the terminal (except for XCurses, because the
       program uses its own window, anyway). Does not restore and save
       again the previous screen contents if CRTSavePreviousScreen was
       called. }
     procedure RestoreTerminalClearCRT; attribute (name
       = 'crt_RestoreTerminalClearCRT');
     
     { Keyboard and character graphics constants -- BP compatible! =:-}
     {$i crt.inc}
     
     var
       { Tells whether the XCurses version of CRT is used }
       XCRT: Boolean = {$ifdef XCURSES} True {$else} False {$endif};
       attribute (name = 'crt_XCRT');
     
       { If True (default: False), the Beep procedure and writing #7 do a
         Flash instead }
       VisualBell: Boolean = False; attribute (name = 'crt_VisualBell');
     
       { Cursor shape codes. Only to be used in very special cases. }
       CursorShapeHidden: Integer = 0; attribute (name
       = 'crt_CursorShapeHidden');
       CursorShapeNormal: Integer = 1; attribute (name
       = 'crt_CursorShapeNormal');
       CursorShapeFull:   Integer = 2; attribute (name
       = 'crt_CursorShapeFull');
     
     type
       TKey = Word;
     
       TCursorShape = (CursorIgnored, CursorHidden, CursorNormal,
       CursorFat, CursorBlock);
     
       TCRTUpdate = (UpdateNever, UpdateWaitInput, UpdateInput,
                     UpdateRegularly, UpdateAlways);
     
       TPoint = record
         x, y: Integer
       end;
     
       PCharAttr = ^TCharAttr;
       TCharAttr = record
         ch       : Char;
         Attr     : TTextAttr;
         PCCharSet: Boolean
       end;
     
       PCharAttrs = ^TCharAttrs;
       TCharAttrs = array [1 .. MaxVarSize div SizeOf (TCharAttr)] of
       TCharAttr;
     
       TWindowXYInternalCard8 = Cardinal attribute (Size = 8);
       TWindowXYInternalFill = Integer attribute (Size = BitSizeOf (Word)
       - 16);
       TWindowXY = packed record
         {$ifdef __BYTES_BIG_ENDIAN__}
         Fill: TWindowXYInternalFill;
         y, x: TWindowXYInternalCard8
         {$elif defined (__BYTES_LITTLE_ENDIAN__)}
         x, y: TWindowXYInternalCard8;
         Fill: TWindowXYInternalFill
         {$else}
         {$error Endianness is not defined!}
         {$endif}
       end;
     
     { Make sure TWindowXY really has the same size as WindMin and
       WindMax. The value of the constant will always be True, and is of
       no further interest. }
     const
       AssertTWindowXYSize = CompilerAssert ((SizeOf (TWindowXY) = SizeOf
       (WindMin)) and
                                             (SizeOf (TWindowXY) = SizeOf
       (WindMax)));
     
     var
       { Window upper and left coordinates. More comfortable to access
         than WindMin, but also *obsolete*. WindMin and WindowMin still
         work, but have the problem that they implicitly limit the window
         size to 255x255 characters. Though that's not really small for a
         text window, it's easily possible to create bigger ones (e.g. in
         an xterm with a small font, on a high resolution screen and/or
         extending over several virutal desktops). When using coordinates
         greater than 254, the corresponding bytes in WindowMin/WindowMax
         will be set to 254, so, e.g., programs which do
         Inc (WindowMin.x) will not fail quite as badly (but probably
         still fail). The routines Window and GetWindow use Integer
         coordinates, and don't suffer from any of these problems, so
         they should be used instead. }
       WindowMin: TWindowXY absolute WindMin;
     
       { Window lower right coordinates. More comfortable to access than
         WindMax, but also *obsolete* (see the comments for WindowMin).
         Use Window and GetWindow instead. }
       WindowMax: TWindowXY absolute WindMax;
     
       { The attribute set by NormVideo }
       NormAttr: TTextAttr = 7; attribute (name = 'crt_NormAttr');
     
       { Tells whether the current mode is monochrome }
       IsMonochrome: Boolean = False; attribute (name
       = 'crt_IsMonochrome');
     
       { This value can be set to a combination of the shFoo constants
         and will be ORed to the actual shift state returned by
         GetShiftState. This can be used to easily simulate shift keys on
         systems where they can't be accessed. }
       VirtualShiftState: Integer = 0; attribute (name
       = 'crt_VirtualShiftState');
     
     { Returns the size of the screen. Note: In BP's WinCRT unit,
       ScreenSize is a variable. But since writing to it from a program
       is pointless, anyway, providing a function here should not cause
       any incompatibility. }
     function  ScreenSize: TPoint; attribute (name
       = 'crt_GetScreenSize');
     
     { Change the screen size if possible. }
     procedure SetScreenSize (x, y: Integer); external
       name 'crt_SetScreenSize';
     
     { Turns colors off or on. }
     procedure SetMonochrome (Monochrome: Boolean); external
       name 'crt_SetMonochrome';
     
     { Tell which modifier keys are currently pressed. The result is a
       combination of the shFoo constants defined in crt.inc, or 0 on
       systems where this function is not supported -- but note
       VirtualShiftState. If supported, ReadKey automatically converts
       kbIns and kbDel keys to kbShIns and kbShDel, resp., if shift is
       pressed. }
     function  GetShiftState: Integer; external name 'crt_GetShiftState';
     
     { Get the extent of the current window. Use this procedure rather
       than reading WindMin and WindMax or WindowMin and WindowMax, since
       this routine allows for window sizes larger than 255. The
       resulting coordinates are 1-based (like in Window, unlike WindMin,
       WindMax, WindowMin and WindowMax). Any of the parameters may be
       Null in case you're interested in only some of the coordinates. }
     procedure GetWindow (var x1, y1, x2, y2: Integer); external
       name 'crt_GetWindow';
     
     { Determine when to update the screen. The possible values are the
       following. The given conditions *guarantee* updates. However,
       updates may occur more frequently (even if the update level is set
       to UpdateNever). About the default value, see the comments for
       CRTInit.
     
       UpdateNever    : never (unless explicitly requested with
                        CRTUpdate)
       UpdateWaitInput: before Delay and CRT input, unless typeahead is
                        detected
       UpdateInput    : before Delay and CRT input
       UpdateRegularly: before Delay and CRT input and otherwise in
                        regular intervals without causing too much
                        refresh. This uses a timer on some systems
                        (currently, Unix with ncurses). This was created
                        for BP compatibility, but for many applications,
                        a lower value causes less flickering in the
                        output, and additionally, timer signals won't
                        disturb other operations. Under DJGPP, this
                        always updates immediately, but this fact should
                        not mislead DJGPP users into thinking this is
                        always so.
       UpdateAlways   : after each output. This can be very slow. (Not so
                        under DJGPP, but this fact should not mislead
                        DJGPP users ...) }
     procedure SetCRTUpdate (UpdateLevel: TCRTUpdate); external
       name 'crt_SetUpdateLevel';
     
     { Do an update now, independently of the update level }
     procedure CRTUpdate; external name 'crt_Update';
     
     { Do an update now and completely redraw the screen }
     procedure CRTRedraw; external name 'crt_Redraw';
     
     { Return Ord (key) for normal keys and $100 * Ord (fkey) for
       function keys }
     function  ReadKeyWord: TKey; external name 'crt_ReadKeyWord';
     
     { Extract the character and scan code from a TKey value }
     function  Key2Char (k: TKey): Char;
     function  Key2Scan (k: TKey): Char;
     
     { Convert a key to upper/lower case if it is a letter, leave it
       unchanged otherwise }
     function  UpCaseKey (k: TKey): TKey;
     function  LoCaseKey (k: TKey): TKey;
     
     { Return key codes for the combination of the given key with Ctrl,
       Alt, AltGr or Extra, resp. Returns 0 if the combination is
       unknown. }
     function  CtrlKey  (ch: Char): TKey; attribute (name
       = 'crt_CtrlKey');
     function  AltKey   (ch: Char): TKey; external name 'crt_AltKey';
     function  AltGrKey (ch: Char): TKey; external name 'crt_AltGrKey';
     function  ExtraKey (ch: Char): TKey; external name 'crt_ExtraKey';
     
     { Check if k is a pseudo key generated by a deadly signal trapped }
     function  IsDeadlySignal (k: TKey): Boolean;
     
     { Produce a beep or a screen flash }
     procedure Beep; external name 'crt_Beep';
     procedure Flash; external name 'crt_Flash';
     
     { Get size of current window (calculated using GetWindow) }
     function  GetXMax: Integer;
     function  GetYMax: Integer;
     
     { Get/goto an absolute position }
     function  WhereXAbs: Integer;
     function  WhereYAbs: Integer;
     procedure GotoXYAbs (x, y: Integer);
     
     { Turn scrolling on or off }
     procedure SetScroll (State: Boolean); external name 'crt_SetScroll';
     
     { Read back whether scrolling is enabled }
     function  GetScroll: Boolean; external name 'crt_GetScroll';
     
     { Determine whether to interpret non-ASCII characters as PC ROM
       characters (True), or in a system dependent way (False). About the
       default, see the comments for CRTInit. }
     procedure SetPCCharSet (PCCharSet: Boolean); external
       name 'crt_SetPCCharSet';
     
     { Read back the value set by SetPCCharSet }
     function  GetPCCharSet: Boolean; external name 'crt_GetPCCharSet';
     
     { Determine whether to interpret #7, #8, #10, #13 as control
       characters (True, default), or as graphics characters (False) }
     procedure SetControlChars (UseControlChars: Boolean); external
       name 'crt_SetControlChars';
     
     { Read back the value set by SetControlChars }
     function  GetControlChars: Boolean; external
       name 'crt_GetControlChars';
     
     procedure SetCursorShape (Shape: TCursorShape); external
       name 'crt_SetCursorShape';
     function  GetCursorShape: TCursorShape; external
       name 'crt_GetCursorShape';
     
     procedure HideCursor;
     procedure HiddenCursor;
     procedure NormalCursor;
     procedure FatCursor;
     procedure BlockCursor;
     procedure IgnoreCursor;
     
     { Simulates a block cursor by writing a block character onto the
       cursor position. The procedure automatically finds the topmost
       visible panel whose shape is not CursorIgnored and places the
       simulated cursor there (just like the hardware cursor), with
       matching attributes, if the cursor shape is CursorFat or
       CursorBlock (otherwise, no simulated cursor is shown).
     
       Calling this procedure again makes the simulated cursor disappear.
       In particular, to get the effect of a blinking cursor, you have to
       call the procedure repeatedly (say, 8 times a second). CRT will
       not do this for you, since it does not intend to be your main
       event loop. }
     procedure SimulateBlockCursor; external
       name 'crt_SimulateBlockCursor';
     
     { Makes the cursor simulated by SimulateBlockCursor disappear if it
       is active. Does nothing otherwise. You should call this procedure
       after using SimulateBlockCursor before doing any further CRT
       output (though failing to do so should not hurt except for
       possibly leaving the simulated cursor in its old position longer
       than it should). }
     procedure SimulateBlockCursorOff; external
       name 'crt_SimulateBlockCursorOff';
     
     function  GetTextColor: Integer;
     function  GetTextBackground: Integer;
     
     { Write string at the given position without moving the cursor.
       Truncated at the right margin. }
     procedure WriteStrAt (x, y: Integer; const s: String; Attr:
       TTextAttr);
     
     { Write (several copies of) a char at then given position without
       moving the cursor. Truncated at the right margin. }
     procedure WriteCharAt (x, y, Count: Integer; ch: Char; Attr:
       TTextAttr);
     
     { Write characters with specified attributes at the given position
       without moving the cursor. Truncated at the right margin. }
     procedure WriteCharAttrAt (x, y, Count: Integer; CharAttr:
       PCharAttrs); external name 'crt_WriteCharAttrAt';
     
     { Write a char while moving the cursor }
     procedure WriteChar (ch: Char);
     
     { Read a character from a screen position }
     procedure ReadChar (x, y: Integer; var ch: Char; var Attr:
       TTextAttr); external name 'crt_ReadChar';
     
     { Change only text attributes, leave characters. Truncated at the
       right margin. }
     procedure ChangeTextAttr (x, y, Count: Integer; NewAttr: TTextAttr);
     
     { Fill current window }
     procedure FillWin (ch: Char; Attr: TTextAttr); external
       name 'crt_FillWin';
     
     { Calculate size of memory required for ReadWin in current window. }
     function  WinSize: SizeType; external name 'crt_WinSize';
     
     { Save window contents. Buf must be WinSize bytes large. }
     procedure ReadWin (var Buf); external name 'crt_ReadWin';
     
     { Restore window contents saved by ReadWin. The size of the current
       window must match the size of the window from which ReadWin was
       used, but the position may be different. }
     procedure WriteWin (const Buf); external name 'crt_WriteWin';
     
     type
       WinState = record
         x1, y1, x2, y2, WhereX, WhereY, NewX1, NewY1, NewX2, NewY2:
       Integer;
         TextAttr: TTextAttr;
         CursorShape: TCursorShape;
         ScreenSize: TPoint;
         Buffer: ^Byte
       end;
     
     { Save window position and size, cursor position, text attribute and
       cursor shape -- *not* the window contents. }
     procedure SaveWin (var State: WinState);
     
     { Make a new window (like Window), and save the contents of the
       screen below the window as well as the position and size, cursor
       position, text attribute and cursor shape of the old window. }
     procedure MakeWin (var State: WinState; x1, y1, x2, y2: Integer);
     
     { Create window in full size, save previous text mode and all values
       that MakeWin does. }
     procedure SaveScreen (var State: WinState);
     
     { Restore the data saved by SaveWin, MakeWin or SaveScreen. }
     procedure RestoreWin (var State: WinState);
     
     { Panels }
     
     type
       TPanel = Pointer;
     
     function  GetActivePanel: TPanel; external
       name 'crt_GetActivePanel';
     procedure PanelNew                 (x1, y1, x2, y2: Integer;
       BindToBackground: Boolean); external name 'crt_PanelNew';
     procedure PanelDelete              (Panel: TPanel); external
       name 'crt_PanelDelete';
     procedure PanelBindToBackground    (Panel: TPanel; BindToBackground:
       Boolean); external name 'crt_PanelBindToBackground';
     function  PanelIsBoundToBackground (Panel: TPanel): Boolean;
       external name 'crt_PanelIsBoundToBackground';
     procedure PanelActivate            (Panel: TPanel); external
       name 'crt_PanelActivate';
     procedure PanelHide                (Panel: TPanel); external
       name 'crt_PanelHide';
     procedure PanelShow                (Panel: TPanel); external
       name 'crt_PanelShow';
     function  PanelHidden              (Panel: TPanel): Boolean;
       external name 'crt_PanelHidden';
     procedure PanelTop                 (Panel: TPanel); external
       name 'crt_PanelTop';
     procedure PanelBottom              (Panel: TPanel); external
       name 'crt_PanelBottom';
     procedure PanelMoveAbove           (Panel, Above: TPanel); external
       name 'crt_PanelMoveAbove';
     procedure PanelMoveBelow           (Panel, Below: TPanel); external
       name 'crt_PanelMoveBelow';
     function  PanelAbove               (Panel: TPanel): TPanel; external
       name 'crt_PanelAbove';
     function  PanelBelow               (Panel: TPanel): TPanel; external
       name 'crt_PanelBelow';
     
     { TPCRT compatibility }
     
     { Write a string at the given position without moving the cursor.
       Truncated at the right margin. }
     procedure WriteString (const s: String; y, x: Integer);
     
     { Write a string at the given position with the given attribute
       without moving the cursor. Truncated at the right margin. }
     procedure FastWriteWindow (const s: String; y, x: Integer; Attr:
       TTextAttr);
     
     { Write a string at the given absolute position with the given
      attribute without moving the cursor. Truncated at the right
       margin. }
     procedure FastWrite       (const s: String; y, x: Integer; Attr:
       TTextAttr);
     
     { WinCRT compatibility }
     
     const
       cw_UseDefault = Integer ($8000);
     
     var
       { Ignored }
       WindowOrg : TPoint = (cw_UseDefault, cw_UseDefault);
       WindowSize: TPoint = (cw_UseDefault, cw_UseDefault);
       Origin    : TPoint = (0, 0);
       InactiveTitle: PChar = '(Inactive %s)';
       AutoTracking: Boolean = True;
       WindowTitle: {$ifdef __BP_TYPE_SIZES__}
                    array [0 .. 79] of Char
                    {$else}
                    TStringBuf
                    {$endif};
     
       { Cursor location, 0-based }
       Cursor    : TPoint = (0, 0); attribute (name = 'crt_Cursor');
     
     procedure InitWinCRT; attribute (name = 'crt_InitWinCRT');
     
     { Halts the program }
     procedure DoneWinCRT; attribute (noreturn, name = 'crt_DoneWinCRT');
     
     procedure WriteBuf (Buffer: PChar; Count: SizeType); attribute (name
       = 'crt_WriteBuf');
     
     function  ReadBuf (Buffer: PChar; Count: SizeType): SizeType;
       attribute (name = 'crt_ReadBuf');
     
     { 0-based coordinates! }
     procedure CursorTo (x, y: Integer); attribute (name
       = 'crt_CursorTo');
     
     { Dummy }
     procedure ScrollTo (x, y: Integer); attribute (name
       = 'crt_ScrollTo');
     
     { Dummy }
     procedure TrackCursor; attribute (name = 'crt_TrackCursor');

Node: Dos, Next: , Previous: CRT, Up: GPC Units

6.15.2 BP compatibility: Dos

The following listing contains the interface of the Dos unit.

This is a portable implementation of most routines from BP's Dos unit. A few routines that are Dos - or even IA32 real mode - specific, are only available if __BP_UNPORTABLE_ROUTINES__ is defined, BP Incompatibilities.

The same functionality and much more is available in the Run Time System, Run Time System. In some cases, the RTS routines have the same interface as the routines in this unit (e.g. GetEnv, FSplit, FExpand, FSearch), in other cases, they have different names and/or easier and less limiting interfaces (e.g. ReadDir etc. vs. FindFirst etc.), and are often more efficient.

Therefore, using this unit is not recommended in newly written programs. 

     { Portable BP compatible Dos unit
     
       This unit supports most of the routines and declarations of BP's
       Dos unit.
     
       Notes:
     
       - The procedures Keep, GetIntVec, SetIntVec are not supported
         since they make only sense for Dos real-mode programs (and GPC
         compiled programs do not run in real-mode, even on IA32 under
         Dos). The procedures Intr and MsDos are only supported under
         DJGPP if __BP_UNPORTABLE_ROUTINES__ is defined (with the
         -D__BP_UNPORTABLE_ROUTINES__ option). A few other routines are
         also only supported with this define, but on all platforms (but
         they are crude hacks, that's why they are not supported without
         this define).
     
       - The internal structure of file variables (FileRec and TextRec)
         is different in GPC. However, as far as TFDDs are concerned,
         there are other ways to achieve the same in GPC, see the GPC
         unit.
     
       Copyright (C) 1998-2004 Free Software Foundation, Inc.
     
       Authors: Frank Heckenbach <frank@pascal.gnu.de>
                Prof. Abimbola A. Olowofoyeku <African_Chief@bigfoot.com>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-,maximum-field-alignment 0}
     {$if __GPC_RELEASE__ < 20030412}
     {$error This unit requires GPC release 20030412 or newer.}
     {$endif}
     
     module Dos;
     
     { GPC and this unit use AnyFile for different meanings. Export
       renaming helps us to avoid a conflict here. If you use both units,
       the meaning of the latter one will be effective, but you always
       get the built-in meaning by using GPC_AnyFile. }
     export Dos = all (DosAnyFile => AnyFile, FSearch, FExpand, FSplit,
       GetEnv);
     
     import GPC (MaxLongInt => Orig_GPC_Maxlongint); System;
     
     type
       GPC_AnyFile = AnyFile;
       Byte8 = Cardinal attribute (Size = 8);
       Word16 = Cardinal attribute (Size = 16);
       Word32 = Cardinal attribute (Size = 32);
       TDosAttr = Word;
     
     const
       { File attribute constants }
       ReadOnly   = $01;
       Hidden     = $02;  { set for dot files except '.' and '..' }
       SysFile    = $04;  { not supported }
       VolumeID   = $08;  { not supported }
       Directory  = $10;
       Archive    = $20;  { means: not executable }
       DosAnyFile = $3f;
     
       { Flag bit masks -- only used by the unportable Dos routines }
       FCarry     = 1;
       FParity    = 4;
       FAuxiliary = $10;
       FZero      = $40;
       FSign      = $80;
       FOverflow  = $800;
     
       { DosError codes }
       DosError_FileNotFound = 2;
       DosError_PathNotFound = 3;
       DosError_AccessDenied = 5;
       DosError_InvalidMem   = 9;
       DosErorr_InvalidEnv   = 10;
       DosError_NoMoreFiles  = 18;
       DosError_IOError      = 29;
       DosError_ReadFault    = 30;
     
     type
       { String types. Not used in this unit, but declared for
         compatibility. }
       ComStr  = String [127];  { Command line string }
       PathStr = String [79];   { File pathname string }
       DirStr  = String [67];   { Drive and directory string }
       NameStr = String [8];    { File name string }
       ExtStr  = String [4];    { File extension string }
     
       TextBuf = array [0 .. 127] of Char;
     
       { Search record used by FindFirst and FindNext }
       SearchRecFill = packed array [1 .. 21] of Byte8;
       SearchRec = record
         Fill: SearchRecFill;
         Attr: Byte8;
         Time,
         Size: LongInt;
         Name: {$ifdef __BP_TYPE_SIZES__}
               String [12]
               {$else}
               TString
               {$endif}
       end;
     
       { Date and time record used by PackTime and UnpackTime }
       DateTime = record
         Year, Month, Day, Hour, Min, Sec: Word
       end;
     
       { 8086 CPU registers -- only used by the unportable Dos routines }
       Registers = record
       case Boolean of
         False: (ax, bx, cx, dx, bp, si, di, ds, es, Flags: Word16);
         True : (al, ah, bl, bh, cl, ch, dl, dh: Byte8)
       end;
     
     var
       { Error status variable }
       DosError: Integer = 0;
     
     procedure GetDate (var Year, Month, Day, DayOfWeek: Word); attribute
       (name = '_p_GetDate');
     procedure GetTime (var Hour, Minute, Second, Sec100: Word);
       attribute (name = '_p_GetTime');
     procedure GetCBreak (var BreakOn: Boolean); attribute (name
       = '_p_GetCBreak');
     procedure SetCBreak (BreakOn: Boolean); attribute (name
       = '_p_SetCBreak');
     { GetVerify and SetVerify are dummies except for DJGPP (in the
       assumption that any real OS knows by itself when and how to verify
       its disks). }
     procedure GetVerify (var VerifyOn: Boolean); attribute (name
       = '_p_GetVerify');
     procedure SetVerify (VerifyOn: Boolean); attribute (name
       = '_p_SetVerify');
     function  DiskFree (Drive: Byte): LongInt; attribute (name
       = '_p_DiskFree');
     function  DiskSize (Drive: Byte): LongInt; attribute (name
       = '_p_DiskSize');
     procedure GetFAttr (var f: GPC_AnyFile; var Attr: TDosAttr);
       attribute (name = '_p_GetFAttr');
     procedure SetFAttr (var f: GPC_AnyFile; Attr: TDosAttr); attribute
       (name = '_p_SetFAttr');
     procedure GetFTime (var f: GPC_AnyFile; var MTime: LongInt);
       attribute (name = '_p_GetFTime');
     procedure SetFTime (var f: GPC_AnyFile; MTime: LongInt); attribute
       (name = '_p_SetFTime');
     
     { FindFirst and FindNext are quite inefficient since they emulate
       all the brain-dead Dos stuff. If at all possible, the standard
       routines OpenDir, ReadDir and CloseDir (in the GPC unit) should be
       used instead. }
     procedure FindFirst (const Path: String; Attr: TDosAttr; var SR:
       SearchRec); attribute (name = '_p_FindFirst');
     procedure FindNext  (var SR: SearchRec); attribute (name
       = '_p_FindNext');
     
     procedure FindClose (var SR: SearchRec); attribute (name
       = '_p_FindClose');
     procedure UnpackTime (p: LongInt; var t: DateTime); attribute (name
       = '_p_UnpackTime');
     procedure PackTime (const t: DateTime; var p: LongInt); attribute
       (name = '_p_PackTime');
     function  EnvCount: Integer;
     function  EnvStr (EnvIndex: Integer): TString;
     procedure SwapVectors;
     { Exec executes a process via Execute, so RestoreTerminal is called
       with the argument True before and False after executing the
       process. }
     procedure Exec (const Path, Params: String);
     function  DosExitCode: Word;
     
     { Unportable Dos-only routines and declarations }
     
     {$ifdef __BP_UNPORTABLE_ROUTINES__}
     {$ifdef __GO32__}
     { These are unportable Dos-only declarations and routines, since
       interrupts are Dos and CPU specific (and have no place in a
       high-level program, anyway). }
     procedure Intr (IntNo: Byte; var Regs: Registers); attribute (name
       = '_p_Intr');
     procedure MsDos (var Regs: Registers); attribute (name
       = '_p_MsDos');
     {$endif}
     
     { Though probably all non-Dos systems have versions numbers as well,
       returning them here would usually not do what is expected, e.g.
       testing if certain Dos features are present by comparing the
       version number. Therefore, this routine always returns 7 (i.e.,
       version 7.0) on non-Dos systems, in the assumption that any real
       OS has at least the features of Dos 7. }
     function  DosVersion: Word; attribute (name = '_p_DosVersion');
     
     { Changing the system date and time is a system administration task,
       not allowed to a normal process. On non-Dos systems, these
       routines emulate the changed date/time, but only for GetTime and
       GetDate (not the RTS date/time routines), and only for this
       process, not for child processes or even the parent process or
       system-wide. }
     procedure SetDate (Year, Month, Day: Word); attribute (name
       = '_p_SetDate');
     procedure SetTime (Hour, Minute, Second, Sec100: Word); attribute
       (name = '_p_SetTime');
     {$endif}

Node: DosUnix, Next: , Previous: Dos, Up: GPC Units

6.15.3 Overcome some differences between Dos and Unix

The following listing contains the interface of the DosUnix unit.

This unit is there to overcome some of those differences between Dos and Unix systems that are not automatically hidden by GPC and the Run Time System. Currently features translation of bash style input/output redirections (foo 2>&1) into redir calls for DJGPP (redir -eo foo) and a way to read files with Dos CR/LF pairs on any system.

When necessary, new features will be added to the unit in future releases. 

     { Some routines to support writing programs portable between Dos and
       Unix. Perhaps it would be a good idea not to put features to make
       Dos programs Unix-compatible (shell redirections) and vice versa
       (reading Dos files from Unix) together into one unit, but rather
       into two units, DosCompat and UnixCompat or so -- let's wait and
       see, perhaps when more routines suited for this/these unit(s) will
       be found, the design will become clearer ...
     
       Copyright (C) 1998-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030412}
     {$error This unit requires GPC release 20030412 or newer.}
     {$endif}
     
     unit DosUnix;
     
     interface
     
     uses GPC;
     
     { This function is meant to be used when you want to invoke a system
       shell command (e.g. via Execute or Exec from the Dos unit) and
       want to specify input/output redirections for the command invoked.
       It caters for the different syntax between DJGPP (with the redir
       utility) and other systems.
     
       To use it, code your redirections in bash style (see the table
       below) in your command line string, pass this string to this
       function, and the function's result to Execute or the other
       routines.
     
       The function translates the following bash style redirections
       (characters in brackets are optional) into a redir call under Dos
       systems except EMX, and leave them unchanged under other systems.
       Note: redir comes with DJGPP, but it should be possible to
       install it on other Dos systems as well. OS/2's shell, however,
       supports bash style redirections, I was told, so we don't
       translate on EMX.
     
       [0]<     file      redirect standard input from file
       [1]>[|]  file      redirect standard output to file
       [1]>>    file      append standard output to file
       [1]>&2             redirect standard output to standard error
       2>[|]    file      redirect standard error to file
       2>>      file      append standard error to file
       2>&1               redirect standard error to standard output
       &> file            redirect both standard output and standard
                          error to file }
     function  TranslateRedirections (const Command: String): TString;
       attribute (name = '_p_TranslateRedirections');
     
     { Under Unix, translates CR/LF pairs to single LF characters when
       reading from f, and back when writing to f. Under Dos, does
       nothing because the run time system alrady does this job. In the
       result, you can read both Dos and Unix files, and files written
       will be Dos. }
     procedure AssignDos (var f: AnyFile; const FileName: String);
       attribute (name = '_p_AssignDos');
     
     { Translates a character from the "OEM" charset used under Dos to
       the ISO-8859-1 (AKA Latin1) character set. }
     function  OEM2Latin1 (ch: Char): Char; attribute (name
       = '_p_OEM2Latin1');
     function  OEM2Latin1Str (const s: String): TString; attribute (name
       = '_p_OEM2Latin1Str');
     
     { Translates a character from the ISO-8859-1 (AKA Latin1) character
       set to the "OEM" charset used under Dos. }
     function  Latin12OEM (ch: Char): Char; attribute (name
       = '_p_Latin12OEM');
     function  Latin12OEMStr (const s: String): TString; attribute (name
       = '_p_Latin12OEMStr');

Node: FileUtils, Next: , Previous: DosUnix, Up: GPC Units

6.15.4 Higher level file and directory handling

The following listing contains the interface of the FileUtils unit.

This unit provides some routines for file and directory handling on a higher level than those provided by the RTS. 

     { Some routines for file and directory handling on a higher level
       than those provided by the RTS.
     
       Copyright (C) 2000-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030412}
     {$error This unit requires GPC release 20030412 or newer.}
     {$endif}
     
     unit FileUtils;
     
     interface
     
     uses GPC;
     
     type
       TStringProc = procedure (const s: String);
     
     { Finds all files matching the given Mask in the given Directory and
       all subdirectories of it. The matching is done using all wildcards
       and brace expansion, like MultiFileNameMatch does. For each file
       found, FileAction is executed. For each directory found (including
       . and .. if they match the Mask!), DirAction is executed. If
       MainDirFirst is True, this happens before processing the files in
       the directory and below, otherwise afterwards. (The former is
       useful, e.g., if this is used to copy a directory tree and
       DirAction does a MkDir, while the latter behaviour is required
       when removing a directory tree and DirAction does a RmDir.) Both
       FileAction and DirAction can be nil in which case nothing is done
       for files or directories found, respectively. (If DirAction is
       nil, the value of DirsFirst does not matter.) Of course,
       FileAction and DirAction may also be identical. The procedure
       leaves InOutRes set in case of any error. If FileAction or
       DirAction return with InOutRes set, FindFiles recognizes this and
       returns immediately. }
     procedure FindFiles (const Directory, Mask: String; MainDirFirst:
       Boolean;
                          FileAction, DirAction: TStringProc); attribute
       (iocritical, name = '_p_FindFiles');
     
     { Creates the directory given by Path and all directories in between
       that are necessary. Does not report an error if the directory
       already exists, but, of course, if it cannot be created because of
       missing permissions or because Path already exists as a file. }
     procedure MkDirs (const Path: String); attribute (iocritical, name
       = '_p_MkDirs');
     
     { Removes Path if empty as well as any empty parent directories.
       Does not report an error if the directory is not empty. }
     procedure RmDirs (const Path: String); attribute (iocritical, name
       = '_p_RmDirs');
     
     { Copies the file Source to Dest, overwriting Dest if it exists and
       can be written to. Returns any errors in IOResult. If Mode >= 0,
       it will change the permissions of Dest to Mode immediately after
       creating it and before writing any data to it. That's useful,
       e.g., if Dest is not meant to be world-readable, because if you'd
       do a ChMod after FileCopy, you might leave the data readable
       (depending on the umask) during the copying. If Mode < 0, Dest
       will be set to the same permissions Source has. In any case, Dest
       will be set to the modification time of Source after copying. On
       any error, the destination file is erased. This is to avoid
       leaving partial files in case of full file systems (one of the
       most common reasons for errors). }
     procedure FileCopy (const Source, Dest: String; Mode: Integer);
       attribute (iocritical, name = '_p_FileCopy');
     
     { Creates a backup of FileName in the directory BackupDirectory or,
       if BackupDirectory is empty, in the directory of FileName. Errors
       are returned in IOResult (and on any error, no partial backup file
       is left), but if FileName does not exist, this does *not* count as
       an error (i.e., BackupFile will just return without setting
       IOResult then). If OnlyUserReadable is True, the backup file will
       be given only user-read permissions, nothing else.
     
       The name chosen for the backup depends on the Simple and Short
       parameters. The short names will fit into 8+3 characters (whenever
       possible), while the long ones conform to the conventions used by
       most GNU tools. If Simple is True, a simple backup file name will
       be used, and previous backups under the same name will be
       overwritten (if possible). Otherwise, backups will be numbered,
       where the number is chosen to be larger than all existing backups,
       so it will be unique and increasing in chronological order. In
       particular:
     
       Simple  Short  Backup name
       True    True   Base name of FileName plus '.bak'
       False   True   Base name of FileName plus '.b' plus a number
       True    False  Base name plus extension of FileName plus '~'
       False   False  Base name plus extension of FileName plus '.~', a
                      number and '~' }
     procedure BackupFile (const FileName, BackupDirectory: String;
       Simple, Short, OnlyUserReadable: Boolean); attribute (iocritical,
       name = '_p_BackupFile');

Node: GMP, Next: , Previous: FileUtils, Up: GPC Units

6.15.5 Arithmetic with unlimited size and precision

The following listing contains the interface of the GMP unit.

This unit provides an interface to the GNU Multiprecision Library to perform arithmetic on integer, rational and real numbers of unlimited size and precision.

To use this unit, you will need the gmp library which can be found in http://www.gnu-pascal.de/libs/. 

     { Definitions for GNU multiple precision functions: arithmetic with
       integer, rational and real numbers of arbitrary size and
       precision.
     
       Translation of the C header (gmp.h) of the GMP library. Tested
       with GMP 2.0.2 and 3.0.1.
     
       To use the GMP unit, you will need the GMP library which can be
       found in http://www.gnu-pascal.de/libs/
     
       Copyright (C) 1998-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License.
     
       Please also note the license of the GMP library. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030303}
     {$error This unit requires GPC release 20030303 or newer.}
     {$endif}
     {$nested-comments}
     
     { If HAVE_GMP3 is set, routines new in GMP 3.x will be made
       available. The define will have no effect on the other interface
       changes between GMP 2.x and 3.x, i.e. the other routines will work
       correctly even if this define is set incorrectly, except on 64 bit
       machines, Crays and other systems where the types are different
       between the GMP versions. Otherwise, the only possible problem if
       setting the define while using GMP 2.x are linking errors if you
       actually use any of the new routines.
     
       If HAVE_GMP4 is set (the default unless HAVE_GMP2 or HAVE_GMP3 are
       set, some interface changes made in GMP 4 are taken into account.
       I.e., if this is set wrong, programs might fail. However, this
       only affects a few routines related to random numbers. }
     {$if not defined (HAVE_GMP2) and not defined (HAVE_GMP3)}
     {$define HAVE_GMP4}
     {$endif}
     
     {$undef GMP}  { in case it's set by the user }
     unit GMP;
     
     interface
     
     uses GPC;
     
     {$if defined (__mips) and defined (_ABIN32) and defined (HAVE_GMP3)}
     { Force the use of 64-bit limbs for all 64-bit MIPS CPUs if ABI
       permits. }
     {$define _LONG_LONG_LIMB}
     {$endif}
     
     type
       {$ifdef _SHORT_LIMB}
       mp_limb_t        = Cardinal;
       mp_limb_signed_t = Integer;
       {$elif defined (_LONG_LONG_LIMB)}
       mp_limb_t        = LongCard;
       mp_limb_signed_t = LongInt;
       {$else}
       mp_limb_t        = MedCard;
       mp_limb_signed_t = MedInt;
       {$endif}
     
       mp_ptr           = ^mp_limb_t;
     
       {$if defined (_CRAY) and not defined (_CRAYMPP) and not defined
       (HAVE_GMP2)}
       mp_size_t        = Integer;
       mp_exp_t         = Integer;
       {$else}
       mp_size_t        = MedInt;
       mp_exp_t         = MedInt;
       {$endif}
     
       mpz_t = record
         mp_alloc,
         mp_size: {$if defined (__MP_SMALL__) and defined (HAVE_GMP2)}
                  ShortInt
                  {$else}
                  Integer
                  {$endif};
         mp_d:    mp_ptr
       end;
     
       mpz_array_ptr = ^mpz_array;
       mpz_array = array [0 .. MaxVarSize div SizeOf (mpz_t) - 1] of
       mpz_t;
     
       mpq_t = record
         mp_num,
         mp_den: mpz_t
       end;
     
       mpf_t = record
         mp_prec,
         mp_size: Integer;
         mp_exp:  mp_exp_t;
         mp_d:    mp_ptr
       end;
     
       TAllocFunction    = function (Size: SizeType): Pointer;
       TReAllocFunction  = function (var Dest: Pointer; OldSize, NewSize:
       SizeType): Pointer;
       TDeAllocProcedure = procedure (Src: Pointer; Size: SizeType);
     
     procedure mp_set_memory_functions (AllocFunction: TAllocFunction;
                                        ReAllocFunction:
       TReAllocFunction;
                                        DeAllocProcedure:
       TDeAllocProcedure); external name '__gmp_set_memory_functions';
     
     function mp_bits_per_limb: Integer; external
       name '_p_mp_bits_per_limb';
     
     {**************** Integer (i.e. Z) routines.  ****************}
     
     procedure mpz_init             (var Dest: mpz_t); external
       name '__gmpz_init';
     procedure mpz_clear            (var Dest: mpz_t); external
       name '__gmpz_clear';
     function  mpz_realloc          (var Dest: mpz_t; NewAlloc:
       mp_size_t): Pointer; external name '__gmpz_realloc';
     procedure mpz_array_init       (Dest: mpz_array_ptr; ArraySize,
       FixedNumBits: mp_size_t); external name '__gmpz_array_init';
     
     procedure mpz_set              (var Dest: mpz_t; protected var Src:
       mpz_t); external name '__gmpz_set';
     procedure mpz_set_ui           (var Dest: mpz_t; Src: MedCard);
       external name '__gmpz_set_ui';
     procedure mpz_set_si           (var Dest: mpz_t; Src: MedInt);
       external name '__gmpz_set_si';
     procedure mpz_set_d            (var Dest: mpz_t; Src: Real);
       external name '__gmpz_set_d';
     procedure mpz_set_q            (var Dest: mpz_t; Src: mpq_t);
       external name '__gmpz_set_q';
     procedure mpz_set_f            (var Dest: mpz_t; Src: mpf_t);
       external name '__gmpz_set_f';
     function  mpz_set_str          (var Dest: mpz_t; Src: CString; Base:
       Integer): Integer; external name '__gmpz_set_str';
     
     procedure mpz_init_set         (var Dest: mpz_t; protected var Src:
       mpz_t); external name '__gmpz_init_set';
     procedure mpz_init_set_ui      (var Dest: mpz_t; Src: MedCard);
       external name '__gmpz_init_set_ui';
     procedure mpz_init_set_si      (var Dest: mpz_t; Src: MedInt);
       external name '__gmpz_init_set_si';
     procedure mpz_init_set_d       (var Dest: mpz_t; Src: Real);
       external name '__gmpz_init_set_d';
     function  mpz_init_set_str     (var Dest: mpz_t; Src: CString; Base:
       Integer): Integer; external name '__gmpz_init_set_str';
     
     function  mpz_get_ui           (protected var Src: mpz_t): MedCard;
       external name '__gmpz_get_ui';
     function  mpz_get_si           (protected var Src: mpz_t): MedInt;
       external name '__gmpz_get_si';
     function  mpz_get_d            (protected var Src: mpz_t): Real;
       external name '__gmpz_get_d';
     { Pass nil for Dest to let the function allocate memory for it }
     function  mpz_get_str          (Dest: CString; Base: Integer;
       protected var Src: mpz_t): CString; external
       name '__gmpz_get_str';
     
     procedure mpz_add              (var Dest: mpz_t; protected var Src1,
       Src2: mpz_t); external name '__gmpz_add';
     procedure mpz_add_ui           (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard); external name '__gmpz_add_ui';
     procedure mpz_sub              (var Dest: mpz_t; protected var Src1,
       Src2: mpz_t); external name '__gmpz_sub';
     procedure mpz_sub_ui           (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard); external name '__gmpz_sub_ui';
     procedure mpz_mul              (var Dest: mpz_t; protected var Src1,
       Src2: mpz_t); external name '__gmpz_mul';
     procedure mpz_mul_ui           (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard); external name '__gmpz_mul_ui';
     procedure mpz_mul_2exp         (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard); external name '__gmpz_mul_2exp';
     procedure mpz_neg              (var Dest: mpz_t; protected var Src:
       mpz_t); external name '__gmpz_neg';
     procedure mpz_abs              (var Dest: mpz_t; protected var Src:
       mpz_t); external name '__gmpz_abs';
     procedure mpz_fac_ui           (var Dest: mpz_t; Src: MedCard);
       external name '__gmpz_fac_ui';
     
     procedure mpz_tdiv_q           (var Dest: mpz_t; protected var Src1,
       Src2: mpz_t); external name '__gmpz_tdiv_q';
     procedure mpz_tdiv_q_ui        (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard); external name '__gmpz_tdiv_q_ui';
     procedure mpz_tdiv_r           (var Dest: mpz_t; protected var Src1,
       Src2: mpz_t); external name '__gmpz_tdiv_r';
     procedure mpz_tdiv_r_ui        (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard); external name '__gmpz_tdiv_r_ui';
     procedure mpz_tdiv_qr          (var DestQ, DestR: mpz_t; protected
       var Src1, Src2: mpz_t); external name '__gmpz_tdiv_qr';
     procedure mpz_tdiv_qr_ui       (var DestQ, DestR: mpz_t; protected
       var Src1: mpz_t; Src2: MedCard); external
       name '__gmpz_tdiv_qr_ui';
     
     procedure mpz_fdiv_q           (var Dest: mpz_t; protected var Src1,
       Src2: mpz_t); external name '__gmpz_fdiv_q';
     function  mpz_fdiv_q_ui        (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard): MedCard; external name '__gmpz_fdiv_q_ui';
     procedure mpz_fdiv_r           (var Dest: mpz_t; protected var Src1,
       Src2: mpz_t); external name '__gmpz_fdiv_r';
     function  mpz_fdiv_r_ui        (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard): MedCard; external name '__gmpz_fdiv_r_ui';
     procedure mpz_fdiv_qr          (var DestQ, DestR: mpz_t; protected
       var Src1, Src2: mpz_t); external name '__gmpz_fdiv_qr';
     function  mpz_fdiv_qr_ui       (var DestQ, DestR: mpz_t; protected
       var Src1: mpz_t; Src2: MedCard): MedCard; external
       name '__gmpz_fdiv_qr_ui';
     function  mpz_fdiv_ui          (protected var Src1: mpz_t; Src2:
       MedCard): MedCard; external name '__gmpz_fdiv_ui';
     
     procedure mpz_cdiv_q           (var Dest: mpz_t; protected var Src1,
       Src2: mpz_t); external name '__gmpz_cdiv_q';
     function  mpz_cdiv_q_ui        (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard): MedCard; external name '__gmpz_cdiv_q_ui';
     procedure mpz_cdiv_r           (var Dest: mpz_t; protected var Src1,
       Src2: mpz_t); external name '__gmpz_cdiv_r';
     function  mpz_cdiv_r_ui        (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard): MedCard; external name '__gmpz_cdiv_r_ui';
     procedure mpz_cdiv_qr          (var DestQ, DestR: mpz_t; protected
       var Src1,Src2: mpz_t); external name '__gmpz_cdiv_qr';
     function  mpz_cdiv_qr_ui       (var DestQ, DestR: mpz_t; protected
       var Src1: mpz_t; Src2: MedCard): MedCard; external
       name '__gmpz_cdiv_qr_ui';
     function  mpz_cdiv_ui          (protected var Src1: mpz_t;
       Src2:MedCard): MedCard; external name '__gmpz_cdiv_ui';
     
     procedure mpz_mod              (var Dest: mpz_t; protected var
       Src1,Src2: mpz_t); external name '__gmpz_mod';
     procedure mpz_divexact         (var Dest: mpz_t; protected var
       Src1,Src2: mpz_t); external name '__gmpz_divexact';
     
     procedure mpz_tdiv_q_2exp      (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard); external name '__gmpz_tdiv_q_2exp';
     procedure mpz_tdiv_r_2exp      (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard); external name '__gmpz_tdiv_r_2exp';
     procedure mpz_fdiv_q_2exp      (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard); external name '__gmpz_fdiv_q_2exp';
     procedure mpz_fdiv_r_2exp      (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard); external name '__gmpz_fdiv_r_2exp';
     
     procedure mpz_powm             (var Dest: mpz_t; protected var Base,
       Exponent, Modulus: mpz_t); external name '__gmpz_powm';
     procedure mpz_powm_ui          (var Dest: mpz_t; protected var Base:
       mpz_t; Exponent: MedCard; protected var Modulus: mpz_t); external
       name '__gmpz_powm_ui';
     procedure mpz_pow_ui           (var Dest: mpz_t; protected var Base:
       mpz_t; Exponent: MedCard); external name '__gmpz_pow_ui';
     procedure mpz_ui_pow_ui        (var Dest: mpz_t; Base, Exponent:
       MedCard); external name '__gmpz_ui_pow_ui';
     
     procedure mpz_sqrt             (var Dest: mpz_t; protected var Src:
       mpz_t); external name '__gmpz_sqrt';
     procedure mpz_sqrtrem          (var Dest, DestR: mpz_t; protected
       var Src: mpz_t); external name '__gmpz_sqrtrem';
     function  mpz_perfect_square_p (protected var Src: mpz_t): Integer;
       external name '__gmpz_perfect_square_p';
     
     function  mpz_probab_prime_p   (protected var Src: mpz_t;
       Repetitions: Integer): Integer; external
       name '__gmpz_probab_prime_p';
     procedure mpz_gcd              (var Dest: mpz_t; protected var Src1,
       Src2: mpz_t); external name '__gmpz_gcd';
     function  mpz_gcd_ui           (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard): MedCard; external name '__gmpz_gcd_ui';
     procedure mpz_gcdext           (var Dest, DestA, DestB: mpz_t;
       protected var SrcA, SrcB: mpz_t); external name '__gmpz_gcdext';
     function  mpz_invert           (var Dest: mpz_t; protected var Src,
       Modulus: mpz_t): Integer; external name '__gmpz_invert';
     function  mpz_jacobi           (protected var Src1, Src2: mpz_t):
       Integer; external name '__gmpz_jacobi';
     
     function  mpz_cmp              (protected var Src1, Src2: mpz_t):
       Integer; external name '__gmpz_cmp';
     function  mpz_cmp_ui           (protected var Src1: mpz_t; Src2:
       MedCard): Integer; external name '__gmpz_cmp_ui';
     function  mpz_cmp_si           (protected var Src1: mpz_t; Src2:
       MedInt): Integer; external name '__gmpz_cmp_si';
     function  mpz_sgn              (protected var Src: mpz_t): Integer;
       attribute (inline);
     
     procedure mpz_and              (var Dest: mpz_t; protected var Src1,
       Src2: mpz_t); external name '__gmpz_and';
     procedure mpz_ior              (var Dest: mpz_t; protected var Src1,
       Src2: mpz_t); external name '__gmpz_ior';
     procedure mpz_com              (var Dest: mpz_t; protected var Src:
       mpz_t); external name '__gmpz_com';
     function  mpz_popcount         (protected var Src: mpz_t): MedCard;
       external name '__gmpz_popcount';
     function  mpz_hamdist          (protected var Src1, Src2: mpz_t):
       MedCard; external name '__gmpz_hamdist';
     function  mpz_scan0            (protected var Src: mpz_t;
       StartingBit: MedCard): MedCard; external name '__gmpz_scan0';
     function  mpz_scan1            (protected var Src: mpz_t;
       StartingBit: MedCard): MedCard; external name '__gmpz_scan1';
     procedure mpz_setbit           (var Dest: mpz_t; BitIndex: MedCard);
       external name '__gmpz_setbit';
     procedure mpz_clrbit           (var Dest: mpz_t; BitIndex: MedCard);
       external name '__gmpz_clrbit';
     
     procedure mpz_random           (var Dest: mpz_t; MaxSize:
       mp_size_t); external name '__gmpz_random';
     procedure mpz_random2          (var Dest: mpz_t; MaxSize:
       mp_size_t); external name '__gmpz_random2';
     function  mpz_sizeinbase       (protected var Src: mpz_t; Base:
       Integer): SizeType; external name '__gmpz_sizeinbase';
     
     {**************** Rational (i.e. Q) routines.  ****************}
     
     procedure mpq_canonicalize     (var Dest: mpq_t); external
       name '__gmpq_canonicalize';
     
     procedure mpq_init             (var Dest: mpq_t); external
       name '__gmpq_init';
     procedure mpq_clear            (var Dest: mpq_t); external
       name '__gmpq_clear';
     procedure mpq_set              (var Dest: mpq_t; protected var Src:
       mpq_t); external name '__gmpq_set';
     procedure mpq_set_z            (var Dest: mpq_t; protected var Src:
       mpz_t); external name '__gmpq_set_z';
     procedure mpq_set_ui           (var Dest: mpq_t; Nom, Den: MedCard);
       external name '__gmpq_set_ui';
     procedure mpq_set_si           (var Dest: mpq_t; Nom: MedInt; Den:
       MedCard); external name '__gmpq_set_si';
     
     procedure mpq_add              (var Dest: mpq_t; protected var Src1,
       Src2: mpq_t); external name '__gmpq_add';
     procedure mpq_sub              (var Dest: mpq_t; protected var Src1,
       Src2: mpq_t); external name '__gmpq_sub';
     procedure mpq_mul              (var Dest: mpq_t; protected var Src1,
       Src2: mpq_t); external name '__gmpq_mul';
     procedure mpq_div              (var Dest: mpq_t; protected var Src1,
       Src2: mpq_t); external name '__gmpq_div';
     procedure mpq_neg              (var Dest: mpq_t; protected var Src:
       mpq_t); external name '__gmpq_neg';
     procedure mpq_inv              (var Dest: mpq_t; protected var Src:
       mpq_t); external name '__gmpq_inv';
     
     function  mpq_cmp              (protected var Src1, Src2: mpq_t):
       Integer; external name '__gmpq_cmp';
     function  mpq_cmp_ui           (protected var Src1: mpq_t; Nom2,
       Den2: MedCard): Integer; external name '__gmpq_cmp_ui';
     function  mpq_sgn              (protected var Src: mpq_t): Integer;
       attribute (inline);
     function  mpq_equal            (protected var Src1, Src2: mpq_t):
       Integer; external name '__gmpq_equal';
     
     function  mpq_get_d            (protected var Src: mpq_t): Real;
       external name '__gmpq_get_d';
     procedure mpq_set_num          (var Dest: mpq_t; protected var Src:
       mpz_t); external name '__gmpq_set_num';
     procedure mpq_set_den          (var Dest: mpq_t; protected var Src:
       mpz_t); external name '__gmpq_set_den';
     procedure mpq_get_num          (var Dest: mpz_t; protected var Src:
       mpq_t); external name '__gmpq_get_num';
     procedure mpq_get_den          (var Dest: mpz_t; protected var Src:
       mpq_t); external name '__gmpq_get_den';
     
     {**************** Float (i.e. R) routines.  ****************}
     
     procedure mpf_set_default_prec (Precision: MedCard); external
       name '__gmpf_set_default_prec';
     procedure mpf_init             (var Dest: mpf_t); external
       name '__gmpf_init';
     procedure mpf_init2            (var Dest: mpf_t; Precision:
       MedCard); external name '__gmpf_init2';
     procedure mpf_clear            (var Dest: mpf_t); external
       name '__gmpf_clear';
     procedure mpf_set_prec         (var Dest: mpf_t; Precision:
       MedCard); external name '__gmpf_set_prec';
     function  mpf_get_prec         (protected var Src: mpf_t): MedCard;
       external name '__gmpf_get_prec';
     procedure mpf_set_prec_raw     (var Dest: mpf_t; Precision:
       MedCard); external name '__gmpf_set_prec_raw';
     
     procedure mpf_set              (var Dest: mpf_t; protected var Src:
       mpf_t); external name '__gmpf_set';
     procedure mpf_set_ui           (var Dest: mpf_t; Src: MedCard);
       external name '__gmpf_set_ui';
     procedure mpf_set_si           (var Dest: mpf_t; Src: MedInt);
       external name '__gmpf_set_si';
     procedure mpf_set_d            (var Dest: mpf_t; Src: Real);
       external name '__gmpf_set_d';
     procedure mpf_set_z            (var Dest: mpf_t; protected var Src:
       mpz_t); external name '__gmpf_set_z';
     procedure mpf_set_q            (var Dest: mpf_t; protected var Src:
       mpq_t); external name '__gmpf_set_q';
     function  mpf_set_str          (var Dest: mpf_t; Src: CString; Base:
       Integer): Integer; external name '__gmpf_set_str';
     
     procedure mpf_init_set         (var Dest: mpf_t; protected var Src:
       mpf_t); external name '__gmpf_init_set';
     procedure mpf_init_set_ui      (var Dest: mpf_t; Src: MedCard);
       external name '__gmpf_init_set_ui';
     procedure mpf_init_set_si      (var Dest: mpf_t; Src: MedInt);
       external name '__gmpf_init_set_si';
     procedure mpf_init_set_d       (var Dest: mpf_t; Src: Real);
       external name '__gmpf_init_set_d';
     function  mpf_init_set_str     (var Dest: mpf_t; Src: CString; Base:
       Integer): Integer; external name '__gmpf_init_set_str';
     
     function  mpf_get_d            (protected var Src: mpf_t): Real;
       external name '__gmpf_get_d';
     { Pass nil for Dest to let the function allocate memory for it }
     function  mpf_get_str          (Dest: CString; var Exponent:
       mp_exp_t; Base: Integer;
                                     NumberOfDigits: SizeType; protected
       var Src: mpf_t): CString; external name '__gmpf_get_str';
     
     procedure mpf_add              (var Dest: mpf_t; protected var Src1,
       Src2: mpf_t); external name '__gmpf_add';
     procedure mpf_add_ui           (var Dest: mpf_t; protected var Src1:
       mpf_t; Src2: MedCard); external name '__gmpf_add_ui';
     procedure mpf_sub              (var Dest: mpf_t; protected var Src1,
       Src2: mpf_t); external name '__gmpf_sub';
     procedure mpf_ui_sub           (var Dest: mpf_t; Src1: MedCard;
       protected var Src2: mpf_t); external name '__gmpf_ui_sub';
     procedure mpf_sub_ui           (var Dest: mpf_t; protected var Src1:
       mpf_t; Src2: MedCard); external name '__gmpf_sub_ui';
     procedure mpf_mul              (var Dest: mpf_t; protected var Src1,
       Src2: mpf_t); external name '__gmpf_mul';
     procedure mpf_mul_ui           (var Dest: mpf_t; protected var Src1:
       mpf_t; Src2: MedCard); external name '__gmpf_mul_ui';
     procedure mpf_div              (var Dest: mpf_t; protected var Src1,
       Src2: mpf_t); external name '__gmpf_div';
     procedure mpf_ui_div           (var Dest: mpf_t; Src1: MedCard;
       protected var Src2: mpf_t); external name '__gmpf_ui_div';
     procedure mpf_div_ui           (var Dest: mpf_t; protected var Src1:
       mpf_t; Src2: MedCard); external name '__gmpf_div_ui';
     procedure mpf_sqrt             (var Dest: mpf_t; protected var Src:
       mpf_t); external name '__gmpf_sqrt';
     procedure mpf_sqrt_ui          (var Dest: mpf_t; Src: MedCard);
       external name '__gmpf_sqrt_ui';
     procedure mpf_neg              (var Dest: mpf_t; protected var Src:
       mpf_t); external name '__gmpf_neg';
     procedure mpf_abs              (var Dest: mpf_t; protected var Src:
       mpf_t); external name '__gmpf_abs';
     procedure mpf_mul_2exp         (var Dest: mpf_t; protected var Src1:
       mpf_t; Src2: MedCard); external name '__gmpf_mul_2exp';
     procedure mpf_div_2exp         (var Dest: mpf_t; protected var Src1:
       mpf_t; Src2: MedCard); external name '__gmpf_div_2exp';
     
     function  mpf_cmp              (protected var Src1, Src2: mpf_t):
       Integer; external name '__gmpf_cmp';
     function  mpf_cmp_si           (protected var Src1: mpf_t; Src2:
       MedInt): Integer;
       {$ifndef HAVE_GMP2} external name '__gmpf_cmp_si'; {$endif}
     function  mpf_cmp_ui           (protected var Src1: mpf_t; Src2:
       MedCard): Integer;
       {$ifndef HAVE_GMP2} external name '__gmpf_cmp_ui'; {$endif}
     function  mpf_eq               (protected var Src1, Src2: mpf_t;
       NumberOfBits: MedCard): Integer; external name '__gmpf_eq';
     procedure mpf_reldiff          (var Dest: mpf_t; protected var Src1,
       Src2: mpf_t); external name '__gmpf_reldiff';
     function  mpf_sgn              (protected var Src: mpf_t): Integer;
       attribute (inline);
     
     procedure mpf_random2          (var Dest: mpf_t; MaxSize: mp_size_t;
       MaxExp: mp_exp_t); external name '__gmpf_random2';
     
     {$if False}  { @@ commented out because they use C file pointers }
     function  mpz_inp_str          (var Dest: mpz_t; Src: CFilePtr;
       Base: Integer): SizeType; external name '__gmpz_inp_str';
     function  mpz_inp_raw          (var Dest: mpz_t; Src: CFilePtr):
       SizeType ; external name '__gmpz_inp_raw';
     function  mpz_out_str          (Dest: CFilePtr; Base: Integer;
       protected var Src: mpz_t): SizeType; external
       name '__gmpz_out_str';
     function  mpz_out_raw          (Dest: CFilePtr; protected var Src:
       mpz_t): SizeType ; external name '__gmpz_out_raw';
     { @@ mpf_out_str has a bug in GMP 2.0.2: it writes a spurious #0
       before the exponent for negative numbers }
     function  mpf_out_str          (Dest: CFilePtr; Base: Integer;
       NumberOfDigits: SizeType; protected var Src: mpf_t): SizeType;
       external name '__gmpf_out_str';
     function  mpf_inp_str          (var Dest: mpf_t; Src: CFilePtr;
       Base: Integer): SizeType; external name '__gmpf_inp_str';
     {$endif}
     
     { New declarations in GMP 3.x. @@ Mostly untested! }
     {$ifndef HAVE_GMP2}
     
     { Available random number generation algorithms. }
     type
       gmp_randalg_t = (GMPRandAlgLC { Linear congruential. });
     
     const
       GMPRandAlgDefault = GMPRandAlgLC;
     
     { Linear congruential data struct. }
     type
       gmp_randata_lc = record
         a: mpz_t;  { Multiplier. }
         c: MedCard;  { Adder. }
         m: mpz_t;  { Modulus (valid only if M2Exp = 0). }
         M2Exp: MedCard;  { If <> 0, modulus is 2 ^ M2Exp. }
       end;
     
     type
       gmp_randstate_t = record
         Seed: mpz_t;  { Current seed. }
         Alg: gmp_randalg_t;  { Algorithm used. }
         AlgData: record  { Algorithm specific data. }
         case gmp_randalg_t of
           GMPRandAlgLC: (lc: ^gmp_randata_lc)  { Linear congruential. }
         end
       end;
     
     procedure gmp_randinit         (var State: gmp_randstate_t; Alg:
       gmp_randalg_t; ...); external name '__gmp_randinit';
     procedure gmp_randinit_lc      (var State: gmp_randstate_t; {$ifdef
       HAVE_GMP4} protected var {$endif} a: mpz_t; c: MedCard; {$ifdef
       HAVE_GMP4} protected var {$endif} m: mpz_t); external
       name '__gmp_randinit_lc';
     procedure gmp_randinit_lc_2exp (var State: gmp_randstate_t; {$ifdef
       HAVE_GMP4} protected var {$endif} a: mpz_t; c: MedCard; M2Exp:
       MedCard); external name '__gmp_randinit_lc_2exp';
     procedure gmp_randseed         (var State: gmp_randstate_t; Seed:
       mpz_t); external name '__gmp_randseed';
     procedure gmp_randseed_ui      (var State: gmp_randstate_t; Seed:
       MedCard); external name '__gmp_randseed_ui';
     procedure gmp_randclear        (var State: gmp_randstate_t);
       external name '__gmp_randclear';
     
     procedure mpz_addmul_ui        (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard); external name '__gmpz_addmul_ui';
     procedure mpz_bin_ui           (var Dest: mpz_t; protected var Src1:
       mpz_t; Src2: MedCard); external name '__gmpz_bin_ui';
     procedure mpz_bin_uiui         (var Dest: mpz_t; Src1, Src2:
       MedCard); external name '__gmpz_bin_uiui';
     function  mpz_cmpabs           (protected var Src1, Src2: mpz_t):
       Integer; external name '__gmpz_cmpabs';
     function  mpz_cmpabs_ui        (protected var Src1: mpz_t; Src2:
       MedCard): Integer; external name '__gmpz_cmpabs_ui';
     procedure mpz_dump             (protected var Src: mpz_t); external
       name '__gmpz_dump';
     procedure mpz_fib_ui           (var Dest: mpz_t; Src: MedCard);
       external name '__gmpz_fib_ui';
     function  mpz_fits_sint_p      (protected var Src: mpz_t): Integer;
       external name '__gmpz_fits_sint_p';
     function  mpz_fits_slong_p     (protected var Src: mpz_t): Integer;
       external name '__gmpz_fits_slong_p';
     function  mpz_fits_sshort_p    (protected var Src: mpz_t): Integer;
       external name '__gmpz_fits_sshort_p';
     function  mpz_fits_uint_p      (protected var Src: mpz_t): Integer;
       external name '__gmpz_fits_uint_p';
     function  mpz_fits_ulong_p     (protected var Src: mpz_t): Integer;
       external name '__gmpz_fits_ulong_p';
     function  mpz_fits_ushort_p    (protected var Src: mpz_t): Integer;
       external name '__gmpz_fits_ushort_p';
     procedure mpz_lcm              (var Dest: mpz_t; protected var Src1,
       Src2: mpz_t); external name '__gmpz_lcm';
     procedure mpz_nextprime        (var Dest: mpz_t; protected var Src:
       mpz_t); external name '__gmpz_nextprime';
     function  mpz_perfect_power_p  (protected var Src: mpz_t): Integer;
       external name '__gmpz_perfect_power_p';
     function  mpz_remove           (var Dest: mpz_t; protected var Src1,
       Src2: mpz_t): MedCard; external name '__gmpz_remove';
     function  mpz_root             (var Dest: mpz_t; protected var Src:
       mpz_t; n: MedCard): Integer; external name '__gmpz_root';
     procedure mpz_rrandomb         (var ROP: mpz_t; var State:
       gmp_randstate_t; n: MedCard); external name '__gmpz_rrandomb';
     procedure mpz_swap             (var v1, v2: mpz_t); external
       name '__gmpz_swap';
     function  mpz_tdiv_ui          (protected var Src1: mpz_t; Src2:
       MedCard): MedCard; external name '__gmpz_tdiv_ui';
     function  mpz_tstbit           (protected var Src1: mpz_t; Src2:
       MedCard): Integer; external name '__gmpz_tstbit';
     procedure mpz_urandomb         ({$ifdef HAVE_GMP4} var {$endif} ROP:
       mpz_t; var State: gmp_randstate_t; n: MedCard); external
       name '__gmpz_urandomb';
     procedure mpz_urandomm         ({$ifdef HAVE_GMP4} var {$endif} ROP:
       mpz_t; var State: gmp_randstate_t; {$ifdef HAVE_GMP4} protected
       var {$endif} n: mpz_t); external name '__gmpz_urandomm';
     procedure mpz_xor              (var Dest: mpz_t; protected var Src1,
       Src2: mpz_t); external name '__gmpz_xor';
     
     procedure mpq_set_d            (var Dest: mpq_t; Src: Real);
       external name '__gmpq_set_d';
     
     procedure mpf_ceil             (var Dest: mpf_t; protected var Src:
       mpf_t); external name '__gmpf_ceil';
     procedure mpf_floor            (var Dest: mpf_t; protected var Src:
       mpf_t); external name '__gmpf_floor';
     {$ifdef HAVE_GMP4}
     function  mpf_get_si           (protected var Src: mpf_t): MedInt;
       external name '__gmpf_get_si';
     function  mpf_get_ui           (protected var Src: mpf_t): MedCard;
       external name '__gmpf_get_ui';
     function  mpf_get_d_2exp       (var Exp: MedInt; protected var Src:
       mpf_t): Real; external name '__gmpf_get_d_2exp';
     {$endif}
     procedure mpf_pow_ui           (var Dest: mpf_t; protected var Src1:
       mpf_t; Src2: MedCard); external name '__gmpf_pow_ui';
     procedure mpf_trunc            (var Dest: mpf_t; protected var Src:
       mpf_t); external name '__gmpf_trunc';
     procedure mpf_urandomb         (ROP: mpf_t; var State:
       gmp_randstate_t; n: MedCard); external name '__gmpf_urandomb';
     
     const
       GMPErrorNone = 0;
       GMPErrorUnsupportedArgument = 1;
       GMPErrorDivisionByZero = 2;
       GMPErrorSqrtOfNegative = 4;
       GMPErrorInvalidArgument = 8;
       GMPErrorAllocate = 16;
     
     var
       gmp_errno: Integer; external name '__gmp_errno';
     
     {$endif}
     
     { Extensions to the GMP library, implemented in this unit }
     
     procedure mpf_exp    (var Dest: mpf_t; protected var Src: mpf_t);
     procedure mpf_ln     (var Dest: mpf_t; protected var Src: mpf_t);
     procedure mpf_pow    (var Dest: mpf_t; protected var Src1, Src2:
       mpf_t);
     {$ifndef HAVE_GMP2}
     procedure mpf_sin    (var Dest: mpf_t; protected var Src: mpf_t);
     procedure mpf_cos    (var Dest: mpf_t; protected var Src: mpf_t);
     {$endif}
     procedure mpf_arctan (var Dest: mpf_t; protected var Src: mpf_t);
     procedure mpf_pi     (var Dest: mpf_t);

Node: GPCUtil, Next: , Previous: GMP, Up: GPC Units

6.15.6 Turbo Power compatibility, etc.

The following listing contains the interface of the GPCUtil unit.

This unit provides some utility routines for compatibility to some units available for BP, like some Turbo Power units. 

     { Some utility routines for compatibility to some units available
       for BP, like some Turbo Power units.
     
       @@NOTE - SOME OF THE ROUTINES IN THIS UNIT MAY NOT WORK CORRECTLY.
       TEST CAREFULLY AND USE WITH CARE!
     
       Copyright (C) 1998-2004 Free Software Foundation, Inc.
     
       Authors: Prof. Abimbola A. Olowofoyeku <African_Chief@bigfoot.com>
                Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030412}
     {$error This unit requires GPC release 20030412 or newer.}
     {$endif}
     
     module GPCUtil;
     
     export GPCUtil = all
            (
             { Return the current working directory }
             GetCurrentDirectory => ThisDirectory,
     
             { Does a directory exist? }
             DirectoryExists => IsDirectory,
     
             { Does file name s exist? }
             FileExists => ExistFile,
     
             { Return just the directory path of Path. Returns
               DirSelf + DirSeparator if Path contains no directory. }
             DirFromPath => JustPathName,
     
             { Return just the file name part without extension of Path.
               Empty if Path contains no file name. }
             NameFromPath => JustFileName,
     
             { Return just the extension of Path. Empty if Path contains
               no extension. }
             ExtFromPath => JustExtension,
     
             { Return the full pathname of Path }
             FExpand => FullPathName,
     
             { Add a DirSeparator to the end of s if there is not
               already one. }
             ForceAddDirSeparator => AddBackSlash,
     
             { Return a string stripped of leading spaces }
             TrimLeftStr => TrimLead,
     
             { Return a string stripped of trailing spaces }
             TrimRightStr => TrimTrail,
     
             { Return a string stripped of leading and trailing spaces }
             TrimBothStr => Trim,
     
             { Convert a string to lowercase }
             LoCaseStr => StLoCase,
     
             { Convert a string to uppercase }
             UpCaseStr => StUpCase
            );
     
     import GPC;
     
     { Replace all occurences of OldC with NewC in s and return the
       result }
     function  ReplaceChar (const s: String; OldC, NewC: Char): TString;
     
     { Break a string into 2 parts, using Ch as a marker }
     function  BreakStr (const Src: String; var Dest1, Dest2: String; ch:
       Char): Boolean; attribute (ignorable);
     
     { Convert a CString to an Integer }
     function  PChar2Int (s: CString): Integer;
     
     { Convert a CString to a LongInt }
     function  PChar2Long (s: CString): LongInt;
     
     { Convert a CString to a Double }
     function  PChar2Double (s: CString): Double;
     
     { Search for s as an executable in the path and return its location
       (full pathname) }
     function  PathLocate (const s: String): TString;
     
     { Copy file Src to Dest and return the number of bytes written }
     function  CopyFile (const Src, Dest: String; BufSize: Integer):
       LongInt; attribute (ignorable);
     
     { Copy file Src to Dest and return the number of bytes written;
       report the number of bytes written versus total size of the source
       file }
     function  CopyFileEx (const Src, Dest: String; BufSize: Integer;
       function Report (Reached, Total: LongInt): LongInt): LongInt;
       attribute (ignorable);
     
     { Turbo Power compatibility }
     
     { Execute the program prog. Dummy1 and Dummy2 are for compatibility
       only; they are ignored. }
     function  ExecDos (const Prog: String; Dummy1: Boolean; Dummy2:
       Pointer): Integer; attribute (ignorable);
     
     { Return whether Src exists in the path as an executable -- if so
       return its full location in Dest }
     function  ExistOnPath (const Src: String; var Dest: String):
       Boolean;
     
     { Change the extension of s to Ext (do not include the dot!) }
     function  ForceExtension (const s, Ext: String): TString;
     
     { Convert Integer to PChar; uses NewCString to allocate memory for
       the result, so you must call StrDispose to free the memory later }
     function  Int2PChar (i: Integer): PChar;
     
     { Convert Integer to string }
     function  Int2Str (i: Integer): TString;
     
     { Convert string to Integer }
     function  Str2Int (const s: String; var i: Integer): Boolean;
       attribute (ignorable);
     
     { Convert string to LongInt }
     function  Str2Long (const s: String; var i: LongInt): Boolean;
       attribute (ignorable);
     
     { Convert string to Double }
     function  Str2Real (const s: String; var i: Double): Boolean;
       attribute (ignorable);
     
     { Return a string right-padded to length Len with ch }
     function  PadCh (const s: String; ch: Char; Len: Integer): TString;
     
     { Return a string right-padded to length Len with spaces }
     function  Pad (const s: String; Len: Integer): TString;
     
     { Return a string left-padded to length Len with ch }
     function  LeftPadCh (const s: String; ch: Char; Len: Byte): TString;
     
     { Return a string left-padded to length Len with blanks }
     function  LeftPad (const s: String; Len: Integer): TString;
     
     { Uniform access to big memory blocks for GPC and BP. Of course, for
       programs that are meant only for GPC, you can use the usual
       New/Dispose routines. But for programs that should compile with
       GPC and BP, you can use the following routines for GPC. In the GPC
       unit for BP (gpc-bp.pas), you can find emulations for BP that try
       to provide access to as much memory as possible, despite the
       limitations of BP. The drawback is that this memory cannot be used
       freely, but only with the following moving routines. }
     
     type
       PBigMem = ^TBigMem;
       TBigMem (MaxNumber: SizeType) = record
         { Public fields }
         Number, BlockSize: SizeType;
         Mappable: Boolean;
         { Private fields }
         Pointers: array [1 .. Max (1, MaxNumber)] of ^Byte
       end;
     
     { Note: the number of blocks actually allocated may be smaller than
       WantedNumber. Check the Number field of the result. }
     function  AllocateBigMem (WantedNumber, aBlockSize: SizeType;
       WantMappable: Boolean): PBigMem;
     procedure DisposeBigMem (p: PBigMem);
     procedure MoveToBigMem (var Source; p: PBigMem; BlockNumber:
       SizeType);
     procedure MoveFromBigMem (p: PBigMem; BlockNumber: SizeType; var
       Dest);
     { Maps a big memory block into normal addressable memory and returns
       its address. The memory must have been allocated with
       WantMappable = True. The mapping is only valid until the next
       MapBigMem call. }
     function  MapBigMem (p: PBigMem; BlockNumber: SizeType): Pointer;

Node: HeapMon, Next: , Previous: GPCUtil, Up: GPC Units

6.15.7 Primitive heap checking

The following listing contains the interface of the HeapMon unit.

This unit provide a rather primitive means to watch the heap, i.e. check if all pointers that were allocated are released again. This is meant as a debugging help for avoiding memory leaks.

More extensive heap checking is provided by libraries like efence which can be used in GPC programs without special provisions. 

     { A unit to watch the heap, i.e. check if all pointers that were
       allocated are released again. It is meant as a debugging help to
       detect memory leaks.
     
       Use it in the main program before all other units. When, at the
       end of the program, some pointers that were allocated, have not
       been released, the unit writes a report to StdErr or another file
       (see below). Only pointers allocated via the Pascal mechanisms
       (New, GetMem) are tracked, not pointers allocated with direct libc
       calls or from C code. After a runtime error, pointers are not
       checked.
     
       Note that many units and libraries allocate memory for their own
       purposes and don't always release it at the end. Therefore, the
       usefulness of this unit is rather limited.
     
       Copyright (C) 1998-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030303}
     {$error This unit requires GPC release 20030303 or newer.}
     {$endif}
     
     unit HeapMon;
     
     interface
     
     uses GPC;
     
     { This unit is automatically activated when used. The following
       declarations are only needed for special purposes. }
     
     { The report generated at the end can be redirected to a certain
       file by pointing HeapMonOutput to it. If not set, the report will
       be printed to the error messages file given with --gpc-rts
       options if given, and StdErr otherwise. }
     var
       HeapMonOutput: ^Text = nil;
     
     { HeapMonReport can be used to print a report on non-released memory
       blocks at an arbitrary point during a program run to the file f.
       It is invoked automatically at the end, so usually you don't have
       to call it. Returns True if any non-released blocks were found,
       False otherwise. }
     function HeapMonReport (var f: Text; DoRestoreTerminal: Boolean):
       Boolean; attribute (ignorable, name = '_p_HeapMonReport');

Node: Intl, Next: , Previous: HeapMon, Up: GPC Units

6.15.8 Internationalization

The following listing contains the interface of the Intl unit.

This unit provides national language support via locales and .mo files. 

     { Welcome to the wonderful world of
       INTERNATIONALIZATION (i18n).
     
       This unit provides the powerful mechanism of national language
       support by accessing .mo files and locale information.
     
       It includes:
         locales (not xlocales) and libintl.
     
       See documentation for gettext (info gettext) for details.
     
       Because GPC can deal with both CStrings and Pascal Strings, there
       is an interface for both types of arguments and function results
       with slightly different names.
     
       E.g. for Pascal strings:
     
         function GetText (const MsgId: String): TString;
     
       And the same as above, but with a C interface:
     
         function GetTextC (MsgId: CString): CString;
     
       PLConv in Pascal is very different from struct lconv * in C.
       Element names do not have underscores and have sometimes different
       sizes. The conversion is done automatically and has correct
       results.
     
       Furthermore, we have a tool similar to xgettext to extract all
       strings out of a Pascal source. It extracts the strings and writes
       a complete .po file to a file. See
       http://www.gnu-pascal.de/contrib/eike/
       The filename is pas2po-VERSION.tar.gz.
     
       Copyright (C) 2001-2004 Free Software Foundation, Inc.
     
       Author: Eike Lange <eike.lange@uni-essen.de>
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU Library General Public License as
       published by the Free Software Foundation, version 2.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       Library General Public License for more details.
     
       You should have received a copy of the GNU Library General Public
       License along with this library; see the file COPYING.LIB. If not,
       write to the Free Software Foundation, Inc., 59 Temple Place -
       Suite 330, Boston, MA 02111-1307, USA. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030303}
     {$error This unit requires GPC release 20030303 or newer.}
     {$endif}
     
     unit Intl;
     
     interface
     
     uses GPC;
     
     type
       IntlString = String (16);
     
       { Pascal translation from OrigLConv in intlc.c }
       PLConv = ^TLConv;
       TLConv = record
         { Numeric (non-monetary) information. }
     
         { Decimal point character. }
         DecimalPoint: IntlString;
     
         { Thousands separator. }
         ThousandsSep: IntlString;
     
         { Each element is the number of digits in each group;
           elements with higher indices are farther left.
           An element with value CharMax means that no further grouping
           is done.
           An element with value Chr (0) means that the previous element
           is used for all groups farther left. }
         Grouping: IntlString;
     
         { Monetary information. }
     
         { First three chars are a currency symbol from ISO 4217.
           Fourth char is the separator.  Fifth char is Chr (0). }
         IntCurrSymbol: IntlString;
     
         { Local currency symbol. }
         CurrencySymbol: IntlString;
     
         { Decimal point character. }
         MonDecimalPoint: IntlString;
     
         { Thousands separator. }
         MonThousandsSep: IntlString;
     
         { Like Grouping element (above). }
         MonGrouping: IntlString;
     
         { Sign for positive values. }
         PositiveSign: IntlString;
     
         { Sign for negative values. }
         NegativeSign: IntlString;
     
         { Int'l fractional digits. }
         IntFracDigits: ByteInt;
     
         { Local fractional digits. }
         FracDigits: ByteInt;
     
         { 1 if CurrencySymbol precedes a positive value, 0 if it
           succeeds. }
         PCSPrecedes: ByteInt;
     
         { 1 iff a space separates CurrencySymbol from a positive
           value. }
         PSepBySpace: ByteInt;
     
         { 1 if CurrencySymbol precedes a negative value, 0 if it
           succeeds. }
         NCSPrecedes: ByteInt;
     
         { 1 iff a space separates CurrencySymbol from a negative
           value. }
         NSepBySpace: ByteInt;
     
         { Positive and negative sign positions:
           0 Parentheses surround the quantity and CurrencySymbol.
           1 The sign string precedes the quantity and CurrencySymbol.
           2 The sign string follows the quantity and CurrencySymbol.
           3 The sign string immediately precedes the CurrencySymbol.
           4 The sign string immediately follows the CurrencySymbol. }
         PSignPosn,
         NSignPosn: ByteInt;
       end;
     
     { Please do not assign anything to these identifiers! }
     var
       LC_CTYPE:    Integer; external name '_p_LC_CTYPE';
       LC_NUMERIC:  Integer; external name '_p_LC_NUMERIC';
       LC_TIME:     Integer; external name '_p_LC_TIME';
       LC_COLLATE:  Integer; external name '_p_LC_COLLATE';
       LC_MONETARY: Integer; external name '_p_LC_MONETARY';
       LC_MESSAGES: Integer; external name '_p_LC_MESSAGES';
       LC_ALL:      Integer; external name '_p_LC_ALL';
       CharMax:     Char; external name '_p_CHAR_MAX';
     
     {@section Locales }
     
     { Set and/or return the current locale. }
     function SetLocale (Category: Integer; const Locale: String):
       TString; attribute (ignorable);
     
     { Set and/or return the current locale. Same as above, but returns
       a CString. }
     function SetLocaleC (Category: Integer; const Locale: String):
       CString; attribute (ignorable);
     
     { Return the numeric/monetary information for the current locale.
       The result is allocated from the heap. You can Dispose it when
       you don't need it anymore. }
     function LocaleConv: PLConv;
     
     {@section GetText }
     
     { Look up MsgId in the current default message catalog for the
       current LC_MESSAGES locale.  If not found, returns MsgId itself
       (the default text). }
     function GetText (const MsgId: String): TString;
     
     { Same as above, but with a C interface }
     function GetTextC (MsgId: CString): CString;
     
     { Look up MsgId in the DomainName message catalog for the current
       LC_MESSAGES locale. }
     function DGetText (const DomainName, MsgId: String): TString;
     
     { Same as above, but with a C interface }
     function DGetTextC (DomainName, MsgId: CString): CString;
     
     { Look up MsgId in the DomainName message catalog for the current
       Category locale. }
     function DCGetText (const DomainName, MsgId: String; Category:
       Integer): TString;
     
     { Same as above, but with a C interface }
     function DCGetTextC (DomainName, MsgId: CString; Category: Integer):
       CString;
     
     { Set the current default message catalog to DomainName.
       If DomainName is empty, reset to the default of messages. }
     function TextDomain (const DomainName: String): TString; attribute
       (ignorable);
     
     { Same as above, but with a C interface.
       If DomainName is nil, return the current default. }
     function TextDomainC (DomainName: CString): CString; attribute
       (ignorable);
     
     { Specify that the DomainName message catalog will be found
       in DirName rather than in the system locale data base. }
     function BindTextDomain (const DomainName, DirName: String):
       TString; attribute (ignorable);
     
     { Same as above, but with a C interface }
     function BindTextDomainC (DomainName, DirName: CString): CString;
       attribute (ignorable);

Node: MD5, Next: , Previous: Intl, Up: GPC Units

6.15.9 MD5 Message Digests

The following listing contains the interface of the MD5 unit.

This unit provides functions to compute MD5 message digest of files or memory blocks, according to the definition of MD5 in RFC 1321 from April 1992. 

     { Functions to compute MD5 message digest of files or memory blocks,
       according to the definition of MD5 in RFC 1321 from April 1992.
     
       Copyright (C) 1995, 1996, 2000-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       Based on the C code written by Ulrich Drepper
       <drepper@gnu.ai.mit.edu>, 1995 as part of glibc.
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU Library General Public License as
       published by the Free Software Foundation, version 2.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       Library General Public License for more details.
     
       You should have received a copy of the GNU Library General Public
       License along with this library; see the file COPYING.LIB. If not,
       write to the Free Software Foundation, Inc., 59 Temple Place -
       Suite 330, Boston, MA 02111-1307, USA. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030303}
     {$error This unit requires GPC release 20030303 or newer.}
     {$endif}
     
     unit MD5;
     
     interface
     
     uses GPC;
     
     { Representation of a MD5 value. It is always in little endian byte
       order and therefore portable. }
     type
       Card8 = Cardinal attribute (Size = 8);
       TMD5 = array [1 .. 16] of Card8;
     
     const
       MD5StrLength = 2 * High (TMD5);
     
     type
       MD5String = String (MD5StrLength);
     
     { Computes MD5 message digest for Length bytes in Buffer. }
     procedure MD5Buffer (const Buffer; Length: SizeType; var MD5: TMD5);
       attribute (name = '_p_MD5Buffer');
     
     { Computes MD5 message digest for the contents of the file f. }
     procedure MD5File (var f: File; var MD5: TMD5); attribute
       (iocritical, name = '_p_MD5File');
     
     { Initializes a MD5 value with zeros. }
     procedure MD5Clear (var MD5: TMD5); attribute (name
       = '_p_MD5Clear');
     
     { Compares two MD5 values for equality. }
     function MD5Compare (const Value1, Value2: TMD5): Boolean; attribute
       (name = '_p_MD5Compare');
     
     { Converts an MD5 value to a string. }
     function MD5Str (const MD5: TMD5) = s: MD5String; attribute (name
       = '_p_MD5Str');
     
     { Converts a string to an MD5 value. Returns True if successful. }
     function MD5Val (const s: String; var MD5: TMD5): Boolean; attribute
       (name = '_p_MD5Val');
     
     { Composes two MD5 values to a single one. }
     function MD5Compose (const Value1, Value2: TMD5) = Dest: TMD5;
       attribute (name = '_p_MD5Compose');

Node: Overlay, Next: , Previous: MD5, Up: GPC Units

6.15.10 BP compatibility: Overlay

The following listing contains the interface of the Overlay unit.

This is just a dummy replacement for BP's Overlay unit, since GPC doesn't need overlays. 

     { Dummy BP compatible overlay unit for GPC
     
       Copyright (C) 1998-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030412}
     {$error This unit requires GPC release 20030412 or newer.}
     {$endif}
     
     unit Overlay;
     
     interface
     
     const
       OvrOK = 0;
       OvrError = -1;
       OvrNotFound = -2;
       OvrNoMemory = -3;
       OvrIOError = -4;
       OvrNoEMSDriver = -5;
       OvrNoEMSMemory = -6;
     
     const
       OvrEmsPages: Word = 0;
       OvrTrapCount: Word = 0;
       OvrLoadCount: Word = 0;
       OvrFileMode: Byte = 0;
     
     type
       OvrReadFunc = function (OvrSeg: Word): Integer;
     
     var
       OvrReadBuf: OvrReadFunc;
       OvrResult: Integer = 0;
     
     procedure OvrInit (aFileName: String); attribute (name
       = '_p_OvrInit');
     procedure OvrInitEMS; attribute (name = '_p_OvrInitEMS');
     procedure OvrSetBuf (Size: LongInt); attribute (name
       = '_p_OvrSetBuf');
     function  OvrGetBuf: LongInt; attribute (name = '_p_OvrGetBuf');
     procedure OvrSetRetry (Size: LongInt); attribute (name
       = '_p_OvrSetRetry');
     function  OvrGetRetry: LongInt; attribute (name = '_p_OvrGetRetry');
     procedure OvrClearBuf; attribute (name = '_p_OvrClearBuf');

Node: Pipes, Next: , Previous: Overlay, Up: GPC Units

6.15.11 Start a child process, connected with pipes, also on Dos

The following listing contains the interface of the Pipes unit.

This unit provides routines to start a child process and write to/read from its Input/Output/StdErr via pipes. All of this is emulated transparently under Dos as far as possible. 

     { Piping data from and to processes
     
       Copyright (C) 1998-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030303}
     {$error This unit requires GPC release 20030303 or newer.}
     {$endif}
     
     { Keep this consistent with the one in pipesc.c }
     {$if defined (MSDOS) or defined (__MINGW32__)}
     {$define NOFORK}
     {$endif}
     
     unit Pipes;
     
     interface
     
     uses GPC;
     
     const
       PipeForking = {$ifdef NOFORK} False {$else} True {$endif};
     
     type
       TProcedure = procedure;
     
       PWaitPIDResult = ^TWaitPIDResult;
       TWaitPIDResult = (PIDNothing, PIDExited, PIDSignaled, PIDStopped,
       PIDUnknown);
     
       PPipeProcess = ^TPipeProcess;
       TPipeProcess = record
         PID      : Integer;         { Process ID of process forked }
         SignalPID: Integer;         { Process ID to send the signal to.
                                       Equals PID by default }
         OpenPipes: Integer;         { Number of pipes to/from the
                                       process, for internal use }
         Signal   : Integer;         { Send this signal (if not 0) to the
                                       process after all pipes have been
                                       closed after some time }
         Seconds  : Integer;         { Wait so many seconds before
                                       sending the signal if the process
                                       has not terminated by itself }
         Wait     : Boolean;         { Wait for the process, even longer
                                       than Seconds seconds, after
                                       sending the signal (if any) }
         Result   : PWaitPIDResult;  { Default nil. If a pointer to a
                                       variable is stored here, its
                                       destination will contain the
                                       information whether the process
                                       terminated by itself, or was
                                       terminated or stopped by a signal,
                                       when waiting after closing the
                                       pipes }
         Status   : ^Integer;        { Default nil. If a pointer to a
                                       variable is stored here, its
                                       destination will contain the exit
                                       status if the process terminated
                                       by itself, or the number of the
                                       signal otherwise, when waiting
                                       after closing the pipes }
       end;
     
     var
       { Default values for TPipeProcess records created by Pipe }
       DefaultPipeSignal : Integer = 0;
       DefaultPipeSeconds: Integer = 0;
       DefaultPipeWait   : Boolean = True;
     
     { The procedure Pipe starts a process whose name is given by
       ProcessName, with the given parameters (can be Null if no
       parameters) and environment, and create pipes from and/or to the
       process' standard input/output/error. ProcessName is searched for
       in the PATH with FSearchExecutable. Any of ToInputFile,
       FromOutputFile and FromStdErrFile can be Null if the corresponding
       pipe is not wanted. FromOutputFile and FromStdErrFile may be
       identical, in which case standard output and standard error are
       redirected to the same pipe. The behaviour of other pairs of files
       being identical is undefined, and useless, anyway. The files are
       Assigned and Reset or Rewritten as appropriate. Errors are
       returned in IOResult. If Process is not Null, a pointer to a
       record is stored there, from which the PID of the process created
       can be read, and by writing to which the action after all pipes
       have been closed can be changed. (The record is automatically
       Dispose'd of after all pipes have been closed.) If automatic
       waiting is turned off, the caller should get the PID from the
       record before it's Dispose'd of, and wait for the process sometime
       in order to avoid zombies. If no redirections are performed (i.e.,
       all 3 files are Null), the caller should wait for the process with
       WaitPipeProcess. When an error occurs, Process is not assigned to,
       and the state of the files is undefined, so be sure to check
       IOResult before going on.
     
       ChildProc, if not nil, is called in the child process after
       forking and redirecting I/O, but before executing the new process.
       It can even be called instead of executing a new process
       (ProcessName can be empty then).
     
       The procedure even works under Dos, but, of course, in a limited
       sense: if ToInputFile is used, the process will not actually be
       started until ToInputFile is closed. Signal, Seconds and Wait of
       TPipeProcess are ignored, and PID and SignalPID do not contain a
       Process ID, but an internal value without any meaning to the
       caller. Result will always be PIDExited. So, Status is the only
       interesting field (but Result should also be checked). Since there
       is no forking under Dos, ChildProc, if not nil, is called in the
       main process before spawning the program. So, to be portable, it
       should not do any things that would influence the process after
       the return of the Pipe function.
     
       The only portable way to use "pipes" in both directions is to call
       Pipe, write all the Input data to ToInputFile, close
       ToInputFile, and then read the Output and StdErr data from
       FromOutputFile and FromStdErrFile. However, since the capacity of
       pipes is limited, one should also check for Data from
       FromOutputFile and FromStdErrFile (using CanRead, IOSelect or
       IOSelectRead) while writing the Input data (under Dos, there
       simply won't be any data then, but checking for data doesn't do
       any harm). Please see pipedemo.pas for an example. }
     procedure MakePipe (var ToInputFile, FromOutputFile, FromStdErrFile:
       AnyFile; const ProcessName: String; protected var Parameters:
       TPStrings; ProcessEnvironment: PCStrings; var Process:
       PPipeProcess; ChildProc: TProcedure); attribute (iocritical);
     
     { Waits for a process created by Pipe as determined in the Process
       record. (Process is Dispose'd of afterwards.) Returns True if
       successful. }
     function WaitPipeProcess (Process: PPipeProcess): Boolean; attribute
       (ignorable);
     
     { Alternative interface from PExecute }
     
     const
       PExecute_First   = 1;
       PExecute_Last    = 2;
       PExecute_One     = PExecute_First or PExecute_Last;
       PExecute_Search  = 4;
       PExecute_Verbose = 8;
     
     { PExecute: execute a chain of processes.
     
       Program and Arguments are the arguments to execv/execvp.
     
       Flags and PExecute_Search is non-zero if $PATH should be searched.
       Flags and PExecute_First is nonzero for the first process in
       chain. Flags and PExecute_Last is nonzero for the last process in
       chain.
     
       The result is the pid on systems like Unix where we fork/exec and
       on systems like MS-Windows and OS2 where we use spawn. It is up to
       the caller to wait for the child.
     
       The result is the exit code on systems like MSDOS where we spawn
       and wait for the child here.
     
       Upon failure, ErrMsg is set to the text of the error message,
       and -1 is returned. errno is available to the caller to use.
     
       PWait: cover function for wait.
     
       PID is the process id of the task to wait for. Status is the
       status argument to wait. Flags is currently unused (allows
       future enhancement without breaking upward compatibility). Pass 0
       for now.
     
       The result is the process ID of the child reaped, or -1 for
       failure.
     
       On systems that don't support waiting for a particular child, PID
       is ignored. On systems like MSDOS that don't really multitask
       PWait is just a mechanism to provide a consistent interface for
       the caller. }
     function  PExecute (ProgramName: CString; Arguments: PCStrings; var
       ErrMsg: String; Flags: Integer): Integer; attribute (ignorable,
       name = '_p_PExecute');
     function  PWait (PID: Integer; var Status: Integer; Flags: Integer):
       Integer; attribute (ignorable, name = '_p_PWait');

Node: Ports, Next: , Previous: Pipes, Up: GPC Units

6.15.12 BP compatibility (partly): Port, PortW arrays

The following listing contains the interface of the Ports unit.

This unit provides access routines for the hardware ports on the IA32, as a partial replacement for BP's Port and PortW pseudo arrays.

Since port access is platform-specific, this unit cannot be used in code intended to be portable. Even on the IA32, its use can often be avoided - e.g. Linux provides a number of ioctl functions, and DJGPP provides some routines to achieve things that would require port access under BP. Therefore, it is recommended to avoid using this unit whenever possible. 

     { Access functions for I/O ports for GPC on an IA32 platform. This
       unit is *not* portable. It works only on IA32 platforms (tested
       under Linux and DJGPP). It is provided here only to serve as a
       replacement for BP's Port and PortW pseudo arrays.
     
       Copyright (C) 1998-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030303}
     {$error This unit requires GPC release 20030303 or newer.}
     {$endif}
     {$ifndef __i386__}
     {$error The Ports unit is only for the IA32 platform}
     {$endif}
     
     unit Ports;
     
     interface
     
     { Port access functions }
     function  InPortB  (PortNumber: ShortWord): Byte;
     function  InPortW  (PortNumber: ShortWord): ShortWord;
     procedure OutPortB (PortNumber: ShortWord; aValue: Byte);
     procedure OutPortW (PortNumber, aValue: ShortWord);
     
     { libc functions for getting access to the ports -- only for root
       processes, of course -- and to give up root privileges after
       getting access to the ports for setuid root programs. Dummies
       under DJGPP. }
     {$ifdef MSDOS}
     function  IOPerm (From, Num: MedCard; On: Integer): Integer;
       attribute (name = 'ioperm');
     function  IOPL (Level: Integer): Integer; attribute (name = 'iopl');
     function  SetEUID (EUID: Integer): Integer; attribute (name
       = 'seteuid');
     {$else}
     function  IOPerm (From, Num: MedCard; On: Integer): Integer;
       external name 'ioperm';
     function  IOPL (Level: Integer): Integer; external name 'iopl';
     function  SetEUID (EUID: Integer): Integer; external name 'seteuid';
     {$endif}

Node: Printer, Next: , Previous: Ports, Up: GPC Units

6.15.13 BP compatibility: Printer, portable

The following listing contains the interface of the Printer unit.

This unit provides printer access, compatible to BP's Printer unit, for Dos (using printer devices) and Unix systems (using printer utilities).

For BP compatibility, the variable Lst is provided, but for newly written programs, it is recommended to use the AssignPrinter procedure on a text file, and close the file when done (thereby committing the printer job). This method allows for sending multiple printer jobs in the same program. 

     { BP compatible printer unit with extensions
     
       Copyright (C) 1998-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030303}
     {$error This unit requires GPC release 20030303 or newer.}
     {$endif}
     
     unit Printer;
     
     interface
     
     uses GPC {$ifndef __OS_DOS__}, Pipes {$endif};
     
     var
       { Dos-like systems: writing to a printer device }
     
       { The file name to write printer output into }
       PrinterDeviceName: PString = @'prn';
     
       { Unix-like systems: printing via a printer program }
     
       { The file name of the printer program. If it contains a '/', it
         will be taken as a complete path, otherwise the file name will
         be searched for in the PATH with FSearchExecutable. }
       PrinterCommand: PString = @'lpr';
     
       { Optional command line parameters for the printer program.
         Ignored when nil. }
       PrinterArguments: PPStrings = nil;
     
       { How to deal with the printer spooler after the printer pipe is
         closed, cf. the Pipes unit. }
       PrinterPipeSignal : Integer = 0;
       PrinterPipeSeconds: Integer = 0;
       PrinterPipeWait   : Boolean = True;
     
     { Text file opened to default printer }
     var
       Lst: Text;
     
     { Assign a file to the printer. Lst will be assigned to the default
       printer at program start, but other files can be assigned to the
       same or other printers (possibly after changing the variables
       above). SpoolerOutput, if not Null, will be redirected from the
       printer spooler's standard output and error. If you use this, note
       that a deadlock might arise when trying to write data to the
       spooler while its output is not being read, though this seems
       quite unlikely, since most printer spoolers don't write so much
       output that could fill a pipe. Under Dos, where no spooler is
       involved, SpoolerOutput, if not Null, will be reset to an empty
       file for compatibility. }
     procedure AssignPrinter (var f: AnyFile; var SpoolerOutput:
       AnyFile);

Node: RegEx, Next: , Previous: Printer, Up: GPC Units

6.15.14 Regular Expression matching and substituting

The following listing contains the interface of the RegEx unit.

This unit provides routines to match strings against regular expressions and perform substitutions using matched subexpressions. Regular expressions are strings with some characters having special meanings. They describe (match) a class of strings. They are similar to wild cards used in file name matching, but much more powerful.

To use this unit, you will need the rx library which can be found in http://www.gnu-pascal.de/libs/. 

     {$nested-comments}
     
     { Regular expression matching and replacement
     
       The RegEx unit provides routines to match strings against regular
       expressions and perform substitutions using matched
       subexpressions.
     
       To use the RegEx unit, you will need the rx library which can be
       found in http://www.gnu-pascal.de/libs/
     
       Regular expressions are strings with some characters having
       special meanings. They describe (match) a class of strings. They
       are similar to wild cards used in file name matching, but much
       more powerful.
     
       There are two kinds of regular expressions supported by this unit,
       basic and extended regular expressions. The difference between
       them is not functionality, but only syntax. The following is a
       short overview of regular expressions. For a more thorough
       explanation see the literature, or the documentation of the rx
       library, or man pages of programs like grep(1) and sed(1).
     
       Basic           Extended        Meaning
       .             .             matches any single character
       [aei-z]       [aei-z]       matches either a, e, or any
                                       character from i to z
       [^aei-z]      [^aei-z]      matches any character but a,
                                       e, or i .. z
                                       To include in such a list the the
                                       characters ], ^, or -, put
                                       them first, anywhere but first, or
                                       first or last, resp.
       [[:alnum:]]   [[:alnum:]]   matches any alphanumeric character
       [^[:digit:]]  [^[:digit:]]  matches anything but a digit
       [a[:space:]]  [a[:space:]]  matches the letter a or a space
                                       character (space, tab)
       ...                             (there are more classes available)
       \w            \w            = [[:alnum:]]
       \W            \W            = [^[:alnum:]]
       ^             ^             matches the empty string at the
                                       beginning of a line
       $             $             matches the empty string at the
                                       end of a line
       *             *             matches zero or more occurences of
                                       the preceding expression
       \+            +             matches one or more occurences of
                                       the preceding expression
       \?            ?             matches zero or one occurence of
                                       the preceding expression
       \{N\}         {N}           matches exactly N occurences of
                                       the preceding expression (N is an
                                       integer number)
       \{M,N\}       {M,N}         matches M to N occurences of the
                                       preceding expression (M and N are
                                       integer numbers, M <= N)
       AB            AB            matches A followed by B (A and B
                                       are regular expressions)
       A\|B          A|B           matches A or B (A and B are
                                       regular expressions)
       \( \)         ( )           forms a subexpression, to override
                                       precedence, and for subexpression
                                       references
       \7            \7            matches the 7'th parenthesized
                                       subexpression (counted by their
                                       start in the regex), where 7 is a
                                       number from 1 to 9 ;-).
                                       *Please note:* using this feature
                                       can be *very* slow or take very
                                       much memory (exponential time and
                                       space in the worst case, if you
                                       know what that means ...).
       \             \             quotes the following character if
                                       it's special (i.e. listed above)
       rest            rest            any other character matches itself
     
       Precedence, from highest to lowest:
       * parentheses (())
       * repetition (*, +, ?, {})
       * concatenation
       * alternation (|)
     
       When performing substitutions using matched subexpressions of a
       regular expression (see ReplaceSubExpressionReferences), the
       replacement string can reference the whole matched expression with
       & or \0, the 7th subexpression with \7 (just like in the
       regex itself, but using it in replacements is not slow), and the
       7th subexpression converted to upper/lower case with \u7 or
       \l7, resp. (which also works for the whole matched expression
       with \u0 or \l0). A verbatim & or \ can be specified with
       \& or \\, resp.
     
       Copyright (C) 1998-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License.
     
       Please also note the license of the rx library. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030303}
     {$error This unit requires GPC release 20030303 or newer.}
     {$endif}
     
     unit RegEx;
     
     interface
     
     uses GPC;
     
     const
       { BasicRegExSpecialChars contains all characters that have
         special meanings in basic regular expressions.
         ExtRegExSpecialChars contains those that have special meanings
         in extended regular expressions. }
       BasicRegExSpecialChars = ['.', '[', ']', '^', '$', '*', '\'];
       ExtRegExSpecialChars   =
       ['.', '[', ']', '^', '$', '*', '+', '?', '{', '}', '|', '(', ')', '\'];
     
     type
       { The type used by the routines of the RegEx unit to store
         regular expressions in an internal format. The fields RegEx,
         RegMatch, ErrorInternal, From and Length are only used
         internally. SubExpressions can be read after NewRegEx and will
         contain the number of parenthesized subexpressions. Error should
         be checked after NewRegEx. It will be nil when it succeeded,
         and contain an error message otherwise. }
       RegExType = record
         RegEx, RegMatch: Pointer;  { Internal }
         ErrorInternal: CString;    { Internal }
         From, Length: Integer;     { Internal }
         SubExpressions: Integer;
         Error: PString
       end;
     
     { Simple interface to regular expression matching. Matches a regular
       expression against a string starting from a specified position.
       Returns the position of the first match, or 0 if it does not
       match, or the regular expression is invalid. }
     function  RegExPosFrom (const Expression: String; ExtendedRegEx,
       CaseInsensitive: Boolean; const s: String; From: Integer):
       Integer; attribute (name = '_p_RegExPosFrom');
     
     { Creates the internal format of a regular expression. If
       ExtendedRegEx is True, Expression is assumed to denote an extended
       regular expression, otherwise a basic regular expression.
       CaseInsensitive determines if the case of letters will be ignored
       when matching the expression. If NewLines is True, NewLine
       characters in a string matched against the expression will be
       treated as dividing the string in multiple lines, so that $ can
       match before the NewLine and ^ can match after. Also, . and
       [^...] will not match a NewLine then. }
     procedure NewRegEx (var RegEx: RegExType; const Expression: String;
       ExtendedRegEx, CaseInsensitive, NewLines: Boolean); attribute
       (name = '_p_NewRegEx');
     
     { Disposes of a regular expression created with NewRegEx. *Must*
       be used after NewRegEx before the RegEx variable becomes invalid
       (i.e., goes out of scope or a pointer pointing to it is Dispose'd
       of). }
     procedure DisposeRegEx (var RegEx: RegExType); external
       name '_p_DisposeRegEx';
     
     { Matches a regular expression created with NewRegEx against a
       string. }
     function  MatchRegEx (var RegEx: RegExType; const s: String;
       NotBeginningOfLine, NotEndOfLine: Boolean): Boolean; attribute
       (name = '_p_MatchRegEx');
     
     { Matches a regular expression created with NewRegEx against a
       string, starting from a specified position. }
     function  MatchRegExFrom (var RegEx: RegExType; const s: String;
       NotBeginningOfLine, NotEndOfLine: Boolean; From: Integer):
       Boolean; attribute (name = '_p_MatchRegExFrom');
     
     { Finds out where the regular expression matched, if MatchRegEx or
       MatchRegExFrom were successful. If n = 0, it returns the
       position of the whole match, otherwise the position of the n'th
       parenthesized subexpression. MatchPosition and MatchLength will
       contain the position (counted from 1) and length of the match, or
       0 if it didn't match. (Note: MatchLength can also be 0 for a
       successful empty match, so check whether MatchPosition is 0 to
       find out if it matched at all.) MatchPosition or MatchLength may
       be Null and is ignored then. }
     procedure GetMatchRegEx (var RegEx: RegExType; n: Integer; var
       MatchPosition, MatchLength: Integer); external
       name '_p_GetMatchRegEx';
     
     { Checks if the string s contains any quoted characters or
       (sub)expression references to the regular expression RegEx created
       with NewRegEx. These are & or \0 for the whole matched
       expression (if OnlySub is not set) and \1 .. \9 for the n'th
       parenthesized subexpression. Returns 0 if it does not contain any,
       and the number of references and quoted characters if it does. If
       an invalid reference (i.e. a number bigger than the number of
       subexpressions in RegEx) is found, it returns the negative value
       of the (first) invalid reference. }
     function  FindSubExpressionReferences (var RegEx: RegExType; const
       s: String; OnlySub: Boolean): Integer; attribute (name
       = '_p_FindSubExpressionReferences');
     
     { Replaces (sub)expression references in ReplaceStr by the actual
       (sub)expressions and unquotes quoted characters. To be used after
       the regular expression RegEx created with NewRegEx was matched
       against s successfully with MatchRegEx or MatchRegExFrom. }
     function  ReplaceSubExpressionReferences (var RegEx: RegExType;
       const s, ReplaceStr: String): TString; attribute (name
       = '_p_ReplaceSubExpressionReferences');
     
     { Returns the string for a regular expression that matches exactly
       one character out of the given set. It can be combined with the
       usual operators to form more complex expressions. }
     function  CharSet2RegEx (const Characters: CharSet): TString;
       attribute (name = '_p_CharSet2RegEx');

Node: Strings, Next: , Previous: RegEx, Up: GPC Units

6.15.15 BP compatibility: Strings

The following listing contains the interface of the Strings unit.

This is a compatibility unit to BP's Strings unit to handle C style #0-terminated strings.

The same functionality and much more is available in the Run Time System, Run Time System, under clearer names (starting with a CString prefix),

Moreover, the use of #0-terminated C-style strings (PChar or CString) is generally not recommended in GPC, since GPC provides ways to deal with Pascal-style strings of arbitrary and dynamic size in a comfortable way, as well as automatic conversion to C-style strings in order to call external C functions.

Therefore, using this unit is not recommended in newly written programs. 

     { BP compatible Strings unit
     
       Copyright (C) 1999-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030303}
     {$error This unit requires GPC release 20030303 or newer.}
     {$endif}
     
     module Strings;
     
     export Strings = all (CStringLength => StrLen, CStringEnd => StrEnd,
                           CStringMove => StrMove, CStringCopy =>
       StrCopy,
                           CStringCopyEnd => StrECopy, CStringLCopy =>
       StrLCopy,
                           CStringCopyString => StrPCopy, CStringCat =>
       StrCat,
                           CStringLCat => StrLCat, CStringComp =>
       StrComp,
                           CStringCaseComp => StrIComp, CStringLComp =>
       StrLComp,
                           CStringLCaseComp => StrLIComp, CStringChPos =>
       StrScan,
                           CStringLastChPos => StrRScan, CStringPos =>
       StrPos,
                           CStringLastPos => StrRPos, CStringUpCase =>
       StrUpper,
                           CStringLoCase => StrLower, CStringIsEmpty =>
       StrEmpty,
                           CStringNew => StrNew);
     
     import GPC;
     
     function StrPas (aString: CString): TString; attribute (name
       = '_p_StrPas');
     procedure StrDispose (s: CString); external name '_p_Dispose';

Node: StringUtils, Next: , Previous: Strings, Up: GPC Units

6.15.16 Higher level string handling

The following listing contains the interface of the StringUtils unit.

This unit provides some routines for string handling on a higher level than those provided by the RTS. 

     { Some routines for string handling on a higher level than those
       provided by the RTS.
     
       Copyright (C) 1999-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030303}
     {$error This unit requires GPC release 20030303 or newer.}
     {$endif}
     
     unit StringUtils;
     
     interface
     
     uses GPC;
     
     { Various routines }
     
     { Appends Source to s, truncating the result if necessary. }
     procedure AppendStr (var s: String; const Source: String);
     
     { Cuts s to MaxLength characters. If s is already MaxLength
       characters or shorter, it doesn't change anything. }
     procedure StrCut (var s: String; MaxLength: Integer);
     
     { Returns the number of disjoint occurences of SubStr in s. Returns
       0 if SubStr is empty. }
     function  StrCount (const SubStr: String; s: String): Integer;
     
     { Returns s, with all disjoint occurences of Source replaced by
       Dest. }
     function  StrReplace (const s, Source, Dest: String): TString;
     
     { Sets of characters accepted for True and False by
       Char2Boolean and StrReadBoolean. }
     var
       CharactersTrue : CharSet = ['Y', 'y'];
       CharactersFalse: CharSet = ['N', 'n'];
     
     { If ch is an element of CharactersTrue, Dest is set to True,
       otherwise if it is an element of CharactersFalse, Dest is set to
       False. In both cases True is returned. If ch is not an element of
       either set, Dest is set to False and False is returned. }
     function  Char2Boolean (ch: Char; var Dest: Boolean): Boolean;
       attribute (ignorable);
     
     { Converts a digit character to its numeric value. Handles every
       base up to 36 (0 .. 9, a .. z, upper and lower case recognized).
       Returns -1 if the character is not a digit at all. If you want to
       use it for a base < 36, you have to check if the result is smaller
       than the base and not equal to -1. }
     function  Char2Digit (ch: Char): Integer;
     
     { Encode a string in a printable format (quoted printable). All
       occurences of EscapeChar within the string are encoded. If
       QuoteHigh is True, all characters above the ASCII range are
       encoded as well (required in "7 bit" environments, as per several
       RFCs). = is always encoded, as required for proper decoding, as
       are all characters below space (control characters), so if you
       don't need an escape char yourself, you can pass #0 for
       EscapeChar. }
     function  QuoteStringEscape (const s: String; EscapeChar: Char;
       QuoteHigh: Boolean): TString;
     
     { Encode a string in a printable format (quoted printable and
       surrounded with "). All occurences of " within the string are
       encoded, so the result string contains exactly two " characters
       (at the beginning and ending). This is useful to store arbitrary
       strings in text files while keeping them as readable as possible
       (which is the goal of the quoted printable encoding in general,
       see RFC 1521, section 5.1) and being able to read them back
       losslessly (with UnQuoteString). }
     function  QuoteString (const s: String): TString;
     
     { Encode a string in a printable format suitable for StrReadEnum.
       All occurences of , within the string are encoded. }
     function  QuoteEnum (const s: String): TString;
     
     { Decode a string encoded by QuoteString (removing the " and
       expanding quoted printable encoded characters). Returns True if
       successful and False if the string has an invalid form. A string
       returned by QuoteString is always valid. }
     function  UnQuoteString (var s: String): Boolean; attribute
       (ignorable);
     
     { Decode a quoted-printable string (not enclosed in ", unlike for
       UnQuoteString). Returns True if successful and False if the string
       has an invalid form. In the latter case, it still decodes as much
       as is valid, even after the error position. }
     function  UnQPString (var s: String): Boolean; attribute
       (ignorable);
     
     { Quotes a string as done in shells, i.e. all special characters are
       enclosed in either " or ', where ", $ and ` are always
       enclosed in ' and ' is always enclosed in ". }
     function  ShellQuoteString (const s: String): TString;
     
     { Replaces all tab characters in s with the appropriate amount of
       spaces, assuming tab stops at every TabSize columns. Returns True
       if successful and False if the expanded string would exceed the
       capacity of s. In the latter case, some, but not all of the tabs
       in s may have been expanded. }
     function  ExpandTabs (var s: String; TabSize: Integer): Boolean;
       attribute (ignorable);
     
     { Returns s, with all occurences of C style escape sequences (e.g.
       \n) replaced by the characters they mean. If AllowOctal is True,
       also octal character specifications (e.g. \007) are replaced. If
       RemoveQuoteChars is True, any other backslashes are removed (e.g.
       \* -> * and \\ -> \), otherwise they are kept, and also
       \\ is left as two backslashes then. }
     function  ExpandCEscapeSequences (const s: String; RemoveQuoteChars,
       AllowOctal: Boolean): TString;
     
     { Routines for TPStrings }
     
     { Initialise a TPStrings variable, allocate Size characters for each
       element. This procedure does not dispose of any previously
       allocated storage, so if you use it on a previously used variable
       without freeing the storage yourself, this might cause memory
       leaks. }
     procedure AllocateTPStrings (var Strings: TPStrings; Size: Integer);
     
     { Clears all elements (set them to empty strings), does not free any
       storage. }
     procedure ClearTPStrings (var Strings: TPStrings);
     
     { Divide a string into substrings, using Separators as separator. A
       single trailing separator is ignored. Further trailing separators
       as well as any leading separators and multiple separators in a row
       produce empty substrings. }
     function TokenizeString (const Source: String; Separators: CharSet):
       PPStrings;
     
     { Divide a string into substrings, using SpaceCharacters as
       separators. The splitting is done according the usual rules of
       shells, using (and removing) single and double quotes and
       QuotingCharacter. Multiple, leading and trailing separators are
       ignored. If there is an error, a message will be stored in ErrMsg
       (if not Null), and nil will be returned. Nil will also be returned
       (without an error message) if s in empty. }
     function ShellTokenizeString (const s: String; var ErrMsg: String):
       PPStrings;
     
     { String parsing routines }
     
     { All the following StrReadFoo functions behave similarly. They read
       items from a string s, starting at index i, to a variable Dest.
       They skip any space characters (spaces and tabs) by incrementing i
       first. They return True if successful, False otherwise. i is
       incremented accordingly if successful, otherwise i is left
       unchanged, apart from the skipping of space characters, and Dest
       is undefined. This behaviour makes it easy to use the functions in
       a row like this:
     
         i := 1;
         if StrReadInt    (s, i, Size)  and StrReadComma (s, i) and
            StrReadQuoted (s, i, Name)  and StrReadComma (s, i) and
            ...
            StrReadReal   (s, i, Angle) and (i > Length (s)) then ...
     
       (The check i > Length (s) is in case you don't want to accept
       trailing "garbage".) }
     
     { Just skip any space characters as described above. }
     procedure StrSkipSpaces (const s: String; var i: Integer);
     
     { Read a quoted string (as produced by QuoteString) from a string
       and unquote the result using UnQuoteString. It is considered
       failure if the result (unquoted) would be longer than the capacity
       of Dest. }
     function  StrReadQuoted (const s: String; var i: Integer; var Dest:
       String): Boolean; attribute (ignorable);
     
     { Read a string delimited with Delimiter from a string and return
       the result with the delimiters removed. It is considered failure
       if the result (without delimiters) would be longer than the
       capacity of Dest. }
     function  StrReadDelimited (const s: String; var i: Integer; var
       Dest: String; Delimiter: Char): Boolean; attribute (ignorable);
     
     { Read a word (consisting of anything but space characters and
       commas) from a string. It is considered failure if the result
       would be longer than the capacity of Dest. }
     function  StrReadWord (const s: String; var i: Integer; var Dest:
       String): Boolean; attribute (ignorable);
     
     { Check that a certain string is contained in s (after possible
       space characters). }
     function  StrReadConst (const s: String; var i: Integer; const
       Expected: String): Boolean; attribute (ignorable);
     
     { A simpler to use version of StrReadConst that expects a ,. }
     function  StrReadComma (const s: String; var i: Integer): Boolean;
       attribute (ignorable);
     
     { Read an integer number from a string. }
     function  StrReadInt (const s: String; var i: Integer; var Dest:
       Integer): Boolean; attribute (ignorable);
     
     { Read a real number from a string. }
     function  StrReadReal (const s: String; var i: Integer; var Dest:
       Real): Boolean; attribute (ignorable);
     
     { Read a Boolean value, represented by a single character
       from CharactersTrue or CharactersFalse (cf. Char2Boolean), from a
       string. }
     function  StrReadBoolean (const s: String; var i: Integer; var Dest:
       Boolean): Boolean; attribute (ignorable);
     
     { Read an enumerated value, i.e., one of the entries of IDs, from a
       string, and stores the ordinal value, i.e., the index in IDs
       (always zero-based) in Dest. }
     function  StrReadEnum (const s: String; var i: Integer; var Dest:
       Integer; const IDs: array of PString): Boolean; attribute
       (ignorable);
     
     { String hash table }
     
     const
       DefaultHashSize = 1403;
     
     type
       THash = Cardinal;
     
       PStrHashList = ^TStrHashList;
       TStrHashList = record
         Next: PStrHashList;
         s: PString;
         i: Integer;
         p: Pointer
       end;
     
       PStrHashTable = ^TStrHashTable;
       TStrHashTable (Size: Cardinal) = record
         CaseSensitive: Boolean;
         Table: array [0 .. Size - 1] of PStrHashList
       end;
     
     function  HashString          (const s: String): THash;
     function  NewStrHashTable     (Size: Cardinal; CaseSensitive:
       Boolean): PStrHashTable;
     procedure AddStrHashTable     (HashTable: PStrHashTable; s: String;
       i: Integer; p: Pointer);
     procedure DeleteStrHashTable  (HashTable: PStrHashTable; s: String);
     function  SearchStrHashTable  (HashTable: PStrHashTable; const s:
       String; var p: Pointer): Integer;  { p may be Null }
     procedure StrHashTableUsage   (HashTable: PStrHashTable; var
       Entries, Slots: Integer);
     procedure DisposeStrHashTable (HashTable: PStrHashTable);

Node: System, Next: , Previous: StringUtils, Up: GPC Units

6.15.17 BP compatibility: System

The following listing contains the interface of the System unit.

This unit contains only BP's more exotic routines which are not recommended to be used in new programs. Most of their functionality can be achieved by more standard means already.

Note: MemAvail and MaxAvail, provided in this unit, cannot easily be achieved by other means. However, it is not recommended to use them on any multi-tasking system at all, where memory is a shared resource. The notes in the unit give some hints about how to avoid using them.

On special request, i.e., by defining the conditionals __BP_TYPE_SIZES__, __BP_RANDOM__ and/or __BP_PARAMSTR_0__, the unit also provides BP compatible integer type sizes, a 100% BP compatible pseudo random number generator and/or BP compatible ParamStr (0) behaviour (the latter, however, only on some systems). 

     { BP and partly Delphi compatible System unit for GPC
     
       This unit is released as part of the GNU Pascal project. It
       implements some rather exotic BP and Delphi compatibility
       features. Even many BP and Delphi programs don't need them, but
       they're here for maximum compatibility. Most of BP's and Delphi's
       System units' features are built into the compiler or the RTS.
     
       Note: The things in this unit are really exotic. If you haven't
       used BP or Delphi before, you don't want to look at this unit. :-)
     
       This unit depends on the conditional defines __BP_TYPE_SIZES__,
       __BP_RANDOM__, __BP_PARAMSTR_0__ and __BP_NO_ALLOCMEM__.
     
       If __BP_TYPE_SIZES__ is defined (with the -D__BP_TYPE_SIZES__
       option), the integer data types will be redefined to the sizes
       they have in BP or Delphi. Note that this might cause problems,
       e.g. when passing var parameters of integer types between units
       that do and don't use System. However, of the BP compatibility
       units, only Dos and WinDos use such parameters, and they have been
       taken care of so they work.
     
       If __BP_RANDOM__ is defined (-D__BP_RANDOM__), this unit will
       provide an exactly BP compatible pseudo random number generator.
       In particular, the range for integer randoms will be truncated to
       16 bits like in BP. The RandSeed variable is provided, and if it's
       set to the same value as BP's RandSeed, it produces exactly the
       same sequence of pseudo random numbers that BP's pseudo random
       number generator does (whoever might need this ... ;-). Even the
       Randomize function will behave exactly like in BP. However, this
       will not be noted unless one explicitly tests for it.
     
       If __BP_PARAMSTR_0__ is defined (-D__BP_PARAMSTR_0__), this
       unit will change the value of ParamStr (0) to that of
       ExecutablePath, overwriting the value actually passed by the
       caller, to imitate BP's/Dos's behaviour. However *note*: On most
       systems, ExecutablePath is *not* guaranteed to return the full
       path, so defining this symbol doesn't change anything. In general,
       you *cannot* expect to find the full executable path, so better
       don't even try it, or your program will (at best) run on some
       systems. For most cases where BP programs access their own
       executable, there are cleaner alternatives available.
     
       If __BP_NO_ALLOCMEM__ is defined (-D__BP_NO_ALLOCMEM__), the
       two Delphi compatible functions AllocMemCount and AllocMemSize
       will not be provided. The advantage is that this unit will not
       have to Mark the heap which makes memory de-/allocations much
       faster if the program doesn't use Mark otherwise.
     
       Copyright (C) 1998-2004 Free Software Foundation, Inc.
     
       Authors: Peter Gerwinski <peter@gerwinski.de>
                Prof. Abimbola A. Olowofoyeku <African_Chief@bigfoot.com>
                Frank Heckenbach <frank@pascal.gnu.de>
                Dominik Freche <dominik.freche@gmx.net>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030303}
     {$error This unit requires GPC release 20030303 or newer.}
     {$endif}
     
     module System;
     
     export System = all (FileMode {$ifdef __BP_TYPE_SIZES__},
       SystemInteger => Integer {$endif});
     
     import GPC (MaxLongInt => GPC_MaxLongInt);
     
     var
       { Chain of procedures to be executed at the end of the program }
       ExitProc: ^procedure = nil;
     
       { Contains all the command line arguments passed to the program,
         concatenated, with spaces between them }
       CmdLine: CString;
     
       {$ifdef __BP_RANDOM__}
       { Random seed, initialized by Randomize, but can also be set
         explicitly }
       RandSeed: Integer attribute (Size = 32) = 0;
       {$endif}
     
     type
       OrigInt = Integer;
       OrigWord = Word;
     
       { Delphi }
       SmallInt = Integer attribute (Size = 16);
       DWord    = Cardinal attribute (Size = 32);
     
       { Short BP compatible type sizes if wanted }
       {$ifdef __BP_TYPE_SIZES__}
       ByteBool      = Boolean attribute (Size = 8);
       WordBool      = Boolean attribute (Size = 16);
       LongBool      = Boolean attribute (Size = 32);
       ShortInt      = Integer attribute (Size = 8);
       SystemInteger = Integer attribute (Size = 16);
       LongInt       = Integer attribute (Size = 32);
       Comp          = Integer attribute (Size = 64);
       Byte          = Cardinal attribute (Size = 8);
       Word          = Cardinal attribute (Size = 16);
       LongWord      = Cardinal attribute (Size = 32);  { Delphi }
       {$else}
       SystemInteger = Integer;
       {$endif}
     
       {$if False}  { @@ doesn't work well (dialec3.pas) -- when GPC gets
       short
                         strings, it will be unnecessary }
       {$ifopt borland-pascal}
       String = String [255];
       {$endif}
       {$endif}
     
     const
       MaxInt     = High (SystemInteger);
       MaxLongInt = High (LongInt);
     
     { Return the lowest-order byte of x }
     function  Lo (x: LongestInt): Byte; attribute (name = '_p_Lo');
     
     { Return the second-lowest-order byte of x }
     function  Hi (x: LongestInt): Byte; attribute (name = '_p_Hi');
     
     { Swap the lowest-order and second-lowest-order bytes, mask out the
       higher-order ones }
     function  Swap (x: LongestInt): Word; attribute (name = '_p_Swap');
     
     { Store the current directory name (on the given drive number if
       drive <> 0) in s }
     procedure GetDir (Drive: Byte; var s: String); attribute (name
       = '_p_GetDir');
     
     { Dummy routine for compatibility. @@Use two overloaded versions
       rather than varargs when possible. }
     procedure SetTextBuf (var f: Text; var Buf; ...); attribute (name
       = '_p_SetTextBuf');
     
     { Mostly useless BP compatible variables }
     var
       SelectorInc: Word = $1000;
       Seg0040: Word = $40;
       SegA000: Word = $a000;
       SegB000: Word = $b000;
       SegB800: Word = $b800;
       Test8086: Byte = 2;
       Test8087: Byte = 3;  { floating-point arithmetic is emulated
                              transparently by the OS if not present
                              in hardware }
       OvrCodeList: Word = 0;
       OvrHeapSize: Word = 0;
       OvrDebugPtr: Pointer = nil;
       OvrHeapOrg: Word = 0;
       OvrHeapPtr: Word = 0;
       OvrHeapEnd: Word = 0;
       OvrLoadList: Word = 0;
       OvrDosHandle: Word = 0;
       OvrEmsHandle: Word = $ffff;
       HeapOrg: Pointer absolute HeapLow;
       HeapPtr: Pointer absolute HeapHigh;
       HeapEnd: Pointer = Pointer (High (PtrCard));
       FreeList: Pointer = nil;
       FreeZero: Pointer = nil;
       StackLimit: Word = 0;
       HeapList: Word = 0;
       HeapLimit: Word = 1024;
       HeapBlock: Word = 8192;
       HeapAllocFlags: Word = 2;
       CmdShow: SystemInteger = 0;
       SaveInt00: Pointer = nil;
       SaveInt02: Pointer = nil;
       SaveInt0C: Pointer = nil;
       SaveInt0D: Pointer = nil;
       SaveInt1B: Pointer = nil;
       SaveInt21: Pointer = nil;
       SaveInt23: Pointer = nil;
       SaveInt24: Pointer = nil;
       SaveInt34: Pointer = nil;
       SaveInt35: Pointer = nil;
       SaveInt36: Pointer = nil;
       SaveInt37: Pointer = nil;
       SaveInt38: Pointer = nil;
       SaveInt39: Pointer = nil;
       SaveInt3A: Pointer = nil;
       SaveInt3B: Pointer = nil;
       SaveInt3C: Pointer = nil;
       SaveInt3D: Pointer = nil;
       SaveInt3E: Pointer = nil;
       SaveInt3F: Pointer = nil;
       SaveInt75: Pointer = nil;
       RealModeRegs: array [0 .. 49] of Byte =
         (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
          0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
          0, 0, 0, 0, 0, 0, 0, 0);
     
     { Mostly useless BP compatible pointer functions }
     function  Ofs (const x): PtrWord; attribute (name = '_p_Ofs');
     function  Seg (const x): PtrWord; attribute (name = '_p_Seg');
     function  Ptr (Seg, Ofs: PtrWord): Pointer; attribute (name
       = '_p_Ptr');
     function  CSeg: PtrWord; attribute (name = '_p_CSeg');
     function  DSeg: PtrWord; attribute (name = '_p_DSeg');
     function  SSeg: PtrWord; attribute (name = '_p_SSeg');
     function  SPtr: PtrWord; attribute (name = '_p_SPtr');
     
     { Routines to handle BP's 6 byte Real type which is formatted like
       this:
     
       47                                                   0
       -|------- -------- -------- -------- --------|--------
        |                                           |
        +----------+                   +------------+
       47 Sign Bit |  8..46 Mantissa   | 0..7 Biased Exponent
     
       This format does not support infinities, NaNs and denormalized
       numbers. The first digit after the binary point is not stored and
       assumed to be 1. (This is called the normalized representation of
       a binary floating point number.)
     
       In GPC, this type is represented by the type BPReal which is
       binary compatible to BP's type, and can therefore be used in
       connection with binary files used by BP programs.
     
       The functions RealToBPReal and BPRealToReal convert between
       this type and GPC's Real type. Apart from that, BPReal should
       be treated as opaque.
     
       The variables BPRealIgnoreOverflow and BPRealIgnoreUnderflow
       determine what to do in the case of overflows and underflows. The
       default values are BP compatible. }
     
     var
       { Ignore overflows, and use the highest possible value instead. }
       BPRealIgnoreOverflow: Boolean = False;
     
       { Ignore underflows, and use 0 instead. This is BP's behaviour,
         but has the disadvantage of diminishing computation precision. }
       BPRealIgnoreUnderflow: Boolean = True;
     
     type
       BPRealInteral = Cardinal attribute (Size = 8);
       BPReal = packed record
         Format: packed array [1 .. 6] of BPRealInteral
       end;
     
     function RealToBPReal (R: Real): BPReal; attribute (name
       = '_p_RealToBPReal');
     function BPRealToReal (const BR: BPReal): Real; attribute (name
       = '_p_BPRealToReal');
     
     { Heap management stuff }
     
     const
       { Possible results for HeapError }
       HeapErrorRunError = 0;
       HeapErrorNil      = 1;
       HeapErrorRetry    = 2;
     
     var
       { If assigned to a function, it will be called when memory
         allocations do not find enough free memory. Its result
         determines if a run time error should be raised (the default),
         or nil should be returned, or the allocation should be retried
         (causing the routine to be called again if the allocation still
         doesn't succeed).
     
         Notes:
     
         - Returning nil can cause some routines of the RTS and units
           (shipped with GPC or third-party) to crash when they don't
           expect nil, so better don't use this mechanism, but rather
           CGetMem where needed.
     
         - Letting the allocation be retried, of course, only makes sense
           if the routine freed some memory before -- otherwise it will
           cause an infinite loop! So, a meaningful HeapError routine
           should dispose of some temporary objects, if available, and
           return HeapErrorRetry, and return HeapErrorRunError when no
           (more) of them are available. }
       HeapError: ^function (Size: Word): SystemInteger = nil;
     
     { Just returns HeapErrorNil. When this function is assigned to
       HeapError, GetMem and New will return a nil pointer instead of
       causing a runtime error when the allocation fails. See the comment
       for HeapError above. }
     function  HeapErrorNilReturn (Size: Word): SystemInteger; attribute
       (name = '_p_HeapErrorNilReturn');
     
     { Return the total free memory/biggest free memory block. Except
       under Win32 and DJGPP, these are expensive routines -- try to
       avoid them. Under Win32, MaxAvail returns the same as MemAvail, so
       don't rely on being able to allocate a block of memory as big as
       MaxAvail indicates. Generally it's preferable to not use these
       functions at all in order to do a safe allocation, but just try to
       allocate the memory needed using CGetMem, and check for a nil
       result. What makes these routines unrealiable is, e.g., that on
       multi-tasking systems, another process may allocate memory after
       you've called MemAvail/MaxAvail and before you get to do the next
       allocation. Also, please note that some systems over-commit
       virtual memory which may cause MemAvail to return a value larger
       than the actual (physical plus swap) memory available. Therefore,
       if you want to be "sure" (modulo the above restrictions) that the
       memory is actually available, use MaxAvail. }
     function  MemAvail: Cardinal; attribute (name = '_p_MemAvail');
     function  MaxAvail: Cardinal; attribute (name = '_p_MaxAvail');
     
     { Delphi compatibility }
     
     function  CompToDouble (x: Comp): Double; attribute (name
       = '_p_CompToDouble');
     function  DoubleToComp (x: Double): Comp; attribute (name
       = '_p_DoubleToComp');
     {$ifndef __BP_NO_ALLOCMEM__}
     function  AllocMemCount: SystemInteger; attribute (name
       = '_p_AllocMemCount');
     function  AllocMemSize: SizeType; attribute (name
       = '_p_AllocMemSize');
     {$endif}
     procedure Assert (Condition: Boolean); attribute (name
       = '_p_System_Assert');
     procedure DefaultAssertErrorProc (const Message, FileName: String;
       LineNumber: SystemInteger; ErrorAddr: Pointer); attribute (name
       = '_p_DefaultAssertErrorProc');
     
     var
       AssertErrorProc: ^procedure (const Message, FileName: String;
       LineNumber: SystemInteger; ErrorAddr: Pointer) =
       @DefaultAssertErrorProc;
       NoErrMsg: Boolean = False;

Node: TFDD, Next: , Previous: System, Up: GPC Units

6.15.18 Some text file tricks

The following listing contains the interface of the TFDD unit.

This unit provides some tricks with text files, e.g. a "tee" file which causes everything written to it to be written to two other files. 

     { Some text file tricks.
     
       Copyright (C) 2002-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030412}
     {$error This unit requires GPC release 20030412 or newer.}
     {$endif}
     
     unit TFDD;
     
     interface
     
     uses GPC;
     
     { Write to multiple files. Everything written to Dest after calling
       this procedure will be written to both File1 and File2. Can be
       chained. }
     procedure MultiFileWrite (var Dest, File1, File2: AnyFile);
       attribute (name = '_p_MultiFileWrite');

Node: Trap, Next: , Previous: TFDD, Up: GPC Units

6.15.19 Trap runtime errors

The following listing contains the interface of the Trap unit.

This unit allows you to trap runtime errors, so a runtime error will not abort the program, but pass the control back to a point within the program. Use with care, and read the notes in the interface, please. 

     { Trapping runtime errors
     
       The Trap unit allows you to trap runtime errors, so a runtime
       error will not abort the program, but pass the control back to a
       point within the program.
     
       The usage is simple. The TrapExec procedure can be called with a
       function (p) as an argument. p must take a Boolean argument. p
       will immediately be called with False given as its argument. When
       a runtime error would otherwise be caused while p is active, p
       will instead be called again with True as its argument. After p
       returns, runtime error trapping ends.
     
       When the program terminates (e.g. by reaching its end or by a Halt
       statement) and a runtime error was trapped during the run, Trap
       will set the ExitCode and ErrorAddr variables to indicate the
       trapped error.
     
       Notes:
     
       - After trapping a runtime error, your program might not be in a
         stable state. If the runtime error was a "minor" one (such as a
         range checking or arithmetic error), it should not be a problem.
         But if you, e.g., write a larger application and use Trap to
         prevent a sudden abort caused by an unexpected runtime error,
         you should make the program terminate regularly as soon as
         possible after a trapped error (perhaps by telling the user to
         save the data, then terminate the program and report the bug to
         you).
     
       - Since the trapping mechanism *jumps* back, it has all the
         negative effects that a (non-local!) goto can have! You should
         be aware of the consequences of all active procedures being
         terminated at an arbitrary point!
     
       - Nested traps are supported, i.e. you can call TrapExec again
         within a routine called by another TrapExec instance. Runtime
         errors trapped within the inner TrapExec invocation will be
         trapped by the inner TrapExec, while runtime errors trapped
         after its termination will be trapped by the outer TrapExec
         again.
     
       Copyright (C) 1996-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030303}
     {$error This unit requires GPC release 20030303 or newer.}
     {$endif}
     
     unit Trap;
     
     interface
     
     uses GPC;
     
     var
       TrappedExitCode: Integer = 0;
       TrappedErrorAddr: Pointer = nil;
       TrappedErrorMessageString: TString = '';
     
     { Trap runtime errors. See the comment at the top. }
     procedure TrapExec (procedure p (Trapped: Boolean)); attribute (name
       = '_p_TrapExec');
     
     { Forget about saved errors from the innermost TrapExec instance. }
     procedure TrapReset; attribute (name = '_p_TrapReset');

Node: Turbo3, Next: , Previous: Trap, Up: GPC Units

6.15.20 BP compatibility: Turbo3

The following listing contains the interface of the Turbo3 unit.

This is a compatibility unit to BP's Turbo3 compatibility unit to TP3. ;-) It is not meant to be used in any newly written code. 

     { Turbo Pascal 3.0 compatibility unit
     
       Copyright (C) 1998-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-}
     {$if __GPC_RELEASE__ < 20030412}
     {$error This unit requires GPC release 20030412 or newer.}
     {$endif}
     
     { @@ Work-around for a problem with COFF debug info. Will hopefully
          disappear with qualified identifiers. }
     {$ifdef __GO32__}
     {$local W-} {$no-debug-info} {$endlocal}
     {$endif}
     
     unit Turbo3;
     
     interface
     
     import System (MemAvail => System_MemAvail,
                    MaxAvail => System_MaxAvail);
            CRT (LowVideo  => CRT_LowVideo,
                 HighVideo => CRT_HighVideo);
     
     var
       Kbd: Text;
       CBreak: Boolean absolute CheckBreak;
     
     procedure AssignKbd (var f: AnyFile);
     function  MemAvail: Integer; attribute (name = '_p_MemAvail3');
     function  MaxAvail: Integer; attribute (name = '_p_MaxAvail3');
     function  LongFileSize (var f: AnyFile): Real;
     function  LongFilePos  (var f: AnyFile): Real;
     procedure LongSeek     (var f: AnyFile; aPosition: Real);
     procedure LowVideo; attribute (name = '_p_LowVideo3');
     procedure HighVideo; attribute (name = '_p_HighVideo3');

Node: WinDos, Previous: Turbo3, Up: GPC Units

6.15.21 BP compatibility: WinDos

The following listing contains the interface of the WinDos unit.

This is a portable implementation of most routines from BP's WinDos unit. A few routines that are Dos - or even IA32 real mode - specific, are only available if __BP_UNPORTABLE_ROUTINES__ is defined, BP Incompatibilities.

The same functionality and much more is available in the Run Time System, Run Time System. The RTS routines usually have different names and/or easier and less limiting interfaces (e.g. ReadDir etc. vs. FindFirst etc.), and are often more efficient.

Therefore, using this unit is not recommended in newly written programs. 

     { Mostly BP compatible portable WinDos unit
     
       This unit supports most, but not all, of the routines and
       declarations of BP's WinDos unit.
     
       Notes:
     
       - The procedures GetIntVec and SetIntVec are not supported since
         they make only sense for Dos real-mode programs (and GPC
         compiled programs do not run in real-mode, even on IA32 under
         Dos). The procedures Intr and MsDos are only supported under
         DJGPP if __BP_UNPORTABLE_ROUTINES__ is defined (with the
         -D__BP_UNPORTABLE_ROUTINES__ option). A few other routines are
         also only supported with this define, but on all platforms (but
         they are crude hacks, that's why they are not supported without
         this define).
     
       - The internal structure of file variables (TFileRec and TTextRec)
         is different in GPC. However, as far as TFDDs are concerned,
         there are other ways to achieve the same in GPC, see the GPC
         unit.
     
       Copyright (C) 1998-2004 Free Software Foundation, Inc.
     
       Author: Frank Heckenbach <frank@pascal.gnu.de>
     
       This file is part of GNU Pascal.
     
       GNU Pascal is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published
       by the Free Software Foundation; either version 2, or (at your
       option) any later version.
     
       GNU Pascal is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.
     
       You should have received a copy of the GNU General Public License
       along with GNU Pascal; see the file COPYING. If not, write to the
       Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
       02111-1307, USA.
     
       As a special exception, if you link this file with files compiled
       with a GNU compiler to produce an executable, this does not cause
       the resulting executable to be covered by the GNU General Public
       License. This exception does not however invalidate any other
       reasons why the executable file might be covered by the GNU
       General Public License. }
     
     {$gnu-pascal,I-,maximum-field-alignment 0}
     {$if __GPC_RELEASE__ < 20030412}
     {$error This unit requires GPC release 20030412 or newer.}
     {$endif}
     
     { @@ Work-around for a problem with COFF debug info. Will hopefully
          disappear with qualified identifiers. }
     {$ifdef __GO32__}
     {$local W-} {$no-debug-info} {$endlocal}
     {$endif}
     
     module WinDos;
     
     export WinDos = all (FCarry, FParity, FAuxiliary, FZero, FSign,
       FOverflow,
                          DosError, GetDate, GetTime, GetCBreak,
       SetCBreak,
                          GetVerify, SetVerify, DiskFree, DiskSize,
                          GetFAttr, SetFAttr, GetFTime, SetFTime,
                          UnpackTime, PackTime,
                          {$ifdef __BP_UNPORTABLE_ROUTINES__}
                          {$ifdef __GO32__}
                          Intr, MsDos,
                          {$endif}
                          DosVersion, SetDate, SetTime,
                          {$endif}
                          CStringGetEnv => GetEnvVar);
     
     import GPC(MaxLongInt => Orig_GPC_Maxlongint); System;
                         Dos (FindFirst  => Dos_FindFirst,
                              FindNext   => Dos_FindNext,
                              FindClose  => Dos_FindClose);
     const
       { File attribute constants }
       faReadOnly  = ReadOnly;
       faHidden    = Hidden;    { set for dot files except . and .. }
       faSysFile   = SysFile;   { not supported }
       faVolumeID  = VolumeID;  { not supported }
       faDirectory = Directory;
       faArchive   = Archive;   { means: not executable }
       faAnyFile   = AnyFile;
     
       { Maximum file name component string lengths }
       fsPathName  = 79;
       fsDirectory = 67;
       fsFileName  = 8;
       fsExtension = 4;
     
       { FileSplit return flags }
       fcExtension = 1;
       fcFileName  = 2;
       fcDirectory = 4;
       fcWildcards = 8;
     
     type
       PTextBuf = ^TTextBuf;
       TTextBuf = TextBuf;
     
       { Search record used by FindFirst and FindNext }
       TSearchRec = record
          Fill: SearchRecFill;
          Attr: Byte8;
          Time, Size: LongInt;
          Name: {$ifdef __BP_TYPE_SIZES__}
                packed array [0 .. 12] of Char
                {$else}
                TStringBuf
                {$endif};
          Reserved: SearchRec
       end;
     
       { Date and time record used by PackTime and UnpackTime }
       TDateTime = DateTime;
     
       { 8086 CPU registers -- only used by the unportable Dos routines }
       TRegisters = Registers;
     
     { FindFirst and FindNext are quite inefficient since they emulate
       all the brain-dead Dos stuff. If at all possible, the standard
       routines OpenDir, ReadDir and CloseDir (in the GPC unit) should be
       used instead. }
     procedure FindFirst (Path: PChar; Attr: Word; var SR: TSearchRec);
       attribute (name = '_p_WFindFirst');
     procedure FindNext  (var SR: TSearchRec); attribute (name
       = '_p_WFindNext');
     procedure FindClose (var SR: TSearchRec); attribute (name
       = '_p_WFindClose');
     function  FileSearch (Dest, FileName, List: PChar): PChar; attribute
       (name = '_p_WFileSearch');
     function  FileExpand (Dest, FileName: PChar): PChar; attribute (name
       = '_p_WFileExpand');
     function  FileSplit (Path, Dir, BaseName, Ext: PChar): Word;
       attribute (name = '_p_WFileSplit');
     function  GetCurDir (Dir: PChar; Drive: Byte): PChar; attribute
       (name = '_p_WGetCurDir');
     procedure SetCurDir (Dir: PChar); attribute (name
       = '_p_WSetCurDir');
     procedure CreateDir (Dir: PChar); attribute (name
       = '_p_WCreateDir');
     procedure RemoveDir (Dir: PChar); attribute (name
       = '_p_WRemoveDir');
     function  GetArgCount: Integer; attribute (name
       = '_p_WGetArgCount');
     function  GetArgStr (Dest: PChar; ArgIndex: Integer; MaxLen: Word):
       PChar; attribute (name = '_p_WGetArgStr');

Node: Borland Pascal, Next: , Previous: Programming, Up: Top

7 A QuickStart Guide from Borland Pascal to GNU Pascal.

This chapter is intended to be a QuickStart guide for programmers who are familiar with Borland Pascal.

Throughout the manual, we talk of "Borland Pascal" or "BP" for short, to refer to Borland Pascal version 7 for Dos protected mode. Other versions of Borland Pascal and Turbo Pascall don't differ too much, but this one was the very last Dos version Borland has published, so in most if not all cases, you can safely substitute the version you're familiar with.

"Borland Pascal" and "Turbo Pascal" are registered trademarks of Borland Inc.

Node: BP Compatibility, Next: , Up: Borland Pascal

7.1 BP Compatibility

GNU Pascal (GPC) is compatible to version 7 of Borland Pascal (BP) to a large extent and comes with portable replacements of the BP standard units.

However, BP is a 16-bit compiler while GPC is a 32/64-bit compiler, so the size of the Integer type, for instance, is 16 bits in BP, but at least 32 bits in GPC. If a BP program has been designed with portability in mind from the ground up, it may work with GPC without any change. Programs which rely on byte order, on the internals or sizes of data types or which use unportable things like interrupts and assembler code, will need to be changed. The following section lists the possible problems with solutions.

The GPC Run Time System (RTS) is fairly complete, and you can use all libraries written for GNU C from GNU Pascal, so there is much less need to use unportable constructs than there was in BP. (For example, BP's Turbo Vision library uses assembler to call a local procedure through a pointer. With GPC you can do this in Pascal just as with global procedures.) Please do not throw away the advantage of full portability by sticking to those workarounds.

We have successfully ported real-world projects (with several 10000s of lines) from BP to GPC, so this is possible for you, too.

Node: BP Incompatibilities, Next: , Previous: BP Compatibility, Up: Borland Pascal

7.2 BP Incompatibilities

This sections lists the remaining incompatibilities of GPC to BP, and the problems you might encounter when porting BP programs from 16-bit Dos to other platforms, and gives solutions for them.

By incompatibilites we mean problems that can arise when trying to compile a valid BP program with GPC. Of course, there are many features in GPC that BP doesn't know, but we call them extensions unless they can break valid BP programs, so they are not mentioned here. The subsequent sections of the Borland Pascal chapter mention a number of useful extensions that you might want to know about but which will not break your BP code.

Some of the differences can be "overcome" by command-line switches. As a summary: 

     --borland-pascal -w --uses=System -D__BP_TYPE_SIZES__ --pack-struct
     -D__BP_RANDOM__ -D__BP_UNPORTABLE_ROUTINES__ -D__BP_PARAMSTR_0__

But please read the following notes, and don't use these switches indiscriminately when not necessary. There are reasons why they are not GPC's defaults.

Node: String type, Next: , Up: BP Incompatibilities

7.2.1 String type

GPC's internal string format (Extended Pascal string schema) is different from BP's. BP compatible short strings will be implemented in GPC soon, but in the meantime, you'll have to live with the difference. In general, GPC's format has many advantages (no length limit of 255 characters, constant and reference parameters always know about their capacity, etc.), but you will see differences if you:

Node: Qualified identifiers, Next: , Previous: String type, Up: BP Incompatibilities

7.2.2 Qualified identifiers

GPC does not yet support qualified identifiers. They will be implemented soon. In the meantime, just don't use them, sorry. (In general, using the same global identifier in different units can easily be confusing, so it's not bad practice to avoid this, anyway.)

Node: Assembler, Next: , Previous: Qualified identifiers, Up: BP Incompatibilities

7.2.3 Assembler

GPC's inline assembler is not compatible to BP's. It uses AT&T syntax, supports a large variety of processors and works together with GPC's optimizer. So, either convert your inline assembly to AT&T syntax, or (usually better) to Pascal, or put it into an external file which you can assemble with your favourite (32 bit) assembler. A tutorial for using the GPC inline assembler is available at
http://www.gnu-pascal.de/contrib/misc/gpcasm.zip

Since many things you usually do with assembler in BP are provided by GPC's Run Time System (RTS), you will not need the inline assembler as often as in BP. (See Portability hints.)

The same applies to BP's inline directive for hand-written machine code. GPC's inline directive works for Pascal routines (see Miscellaneous), so you'll have to convert any hand-written machine code to Pascal (and thereby make it more readable, portable and easier to maintain while still getting the performance of inline code).

Node: Move; FillChar, Next: , Previous: Assembler, Up: BP Incompatibilities

7.2.4 Move; FillChar

GPC supports Move and FillChar, and they're fully BP compatible. However, some data structures have different internal formats which may become relevant when using these procedures. E.g., using Move on file variables does not work in GPC (there are reasons why assigning file variables with := is not allowed in Pascal, and circumventing this restriction with Move is not a good idea). For other examples, see String type, Real type, and Endianness assumptions.

Node: Real type, Next: , Previous: Move; FillChar, Up: BP Incompatibilities

7.2.5 Real type

GPC does not support BP's 6-byte Real type. It supports Single, Double and Extended which, at least on the IA32 and some other processors, are compatible to BP.

For BP's 6-byte Real type, GPC's System unit provides an emulation, called BPReal, as well as conversion routines to GPC's Real type (which is the same as Double), called RealToBPReal and BPRealToReal. You'll probably only need them when reading or writing binary files containing values of the BP 6-byte real type. There are no operators (e.g., +) available for BPReal, but since GPC supports operator overloading, you could define them yourself (e.g., convert to Real, do the operation, and convert back). Needless to say that this is very inefficient and should not be done for any serious computations. Better convert your data after reading them from the file and before writing them back, or simply convert your data files once (the other types are more efficient even with BP on any non-prehistoric processor, anyway).

Node: Graph unit, Next: , Previous: Real type, Up: BP Incompatibilities

7.2.6 Graph unit

A mostly BP compatible Graph unit exists as part of the GRX package. It is known to work under DJGPP, Cygwin, mingw, Linux/IA32 with svgalib, and should work under any Unix system with X11 (tested under Linux, Solaris, AIX, etc.).

There is a small difference in the color numbering, but it should be easy to work-around: You can't assume, e.g., that color 1 is always blue, and 2 is green, etc. On a system with 15 or more bits of color depth (i.e., 32768 or more colors, which most PCs today have), they will all be very dark shades of blue. This is not really a bug, but simply a property of modern high colors modes (whereas BP's Graph unit was only designed for 16 and 256 color modes).

However, the names Blue, Green etc. stand for the correct colors in the Graph unit of GRX. They are no constants, but functions (because the color depth is in general not known until runtime), so you can't use them in contexts where constants are expected. Also, they might conflict with the identifiers of the CRT unit if you use both units at the same time. If you want to use computed color values in the range 0 ... 15, you can translate them to the correct colors using the EGAColor function.

Node: OOP units, Next: , Previous: Graph unit, Up: BP Incompatibilities

7.2.7 OOP units

The OOP stuff (Turbo Vision etc.) is not yet completed, but work on several projects is underway. If you want information about the current status or access to development source, please contact the GPC mailing list.

Node: Keep; GetIntVec; SetIntVec, Next: , Previous: OOP units, Up: BP Incompatibilities

7.2.8 Keep; GetIntVec; SetIntVec

The routines Keep, GetIntVec and SetIntVec in the Dos unit do not even make sense on DJGPP (32 bit Dos extender). If your program uses these, it is either a low-level Dos utility for which porting to a 32 bit environment might cause bigger problems (because the internal issues of DPMI become relevant which are usually hidden by DJGPP), or it installs interrupt handlers which will have to be thought about more carefully because of things like locking memory, knowing about and handling the differences between real and protected mode interrupts, etc. For these kinds of things, we refer you to the DJGPP FAQ (see DJGPP FAQ).

Node: TFDDs, Next: , Previous: Keep; GetIntVec; SetIntVec, Up: BP Incompatibilities

7.2.9 TFDDs

The internal structure of file variables (FileRec and TextRec in BP's Dos unit and TFileRec and TTextRec in BP's WinDos unit) is different in GPC. However, as far as Text File Device Drivers (TFDDs) are concerned, GPC offers a more powerful mechanism. Please see the RTS reference (see Run Time System), under AssignTFDD.

Node: Mem; Port; Ptr; Seg; Ofs; PrefixSeg; etc., Next: , Previous: TFDDs, Up: BP Incompatibilities

7.2.10 Mem; Port; Ptr; Seg; Ofs; PrefixSeg; etc.

Those few routines in the System unit that deal with segmented pointers (e.g., Ptr) are emulated in such a way that such ugly BP constructs like 

     PInteger (Ptr (Seg (a), Ofs (a) + 6 * SizeOf (Integer)))^ = 42
work in GPC, but they do not provide access to absolute memory addresses. Neither do absolute variables (which take a simple address in the program's address space in GPC, rather than a segmented address), and the Mem and Port arrays don't exist in GPC.

As a replacement for Port on IA32 processors, you can use the routines provided in the Ports unit, Ports. If you want to access absolute memory addresses in the first megabyte under DJGPP, you can't do this with normal pointers because DJGPP programs run in a protected memory environment, unless you use a dirty trick called near pointer hack. Please see the DJGPP FAQ (see DJGPP FAQ) for this and for other ways.

For similar reasons, the variable PrefixSeg in the System unit is not supported. Apart from TSRs, its only meaningful use in BP might be the setting of environment variables. GPC provides the SetEnv and UnSetEnv procedures for this purpose which you can use instead of any BP equivalents based on PrefixSeg. (However note that they will modify the program's own and its childs' environment, not its parent's environment. This is a property - most people call it a feature - of the environments, including DJGPP, that GPC compiled programs run in.)

Node: Endianness assumptions, Next: , Previous: Mem; Port; Ptr; Seg; Ofs; PrefixSeg; etc., Up: BP Incompatibilities

7.2.11 Endianness assumptions

GPC also runs on big-endian systems (see Endianness). This is, of course, a feature of GPC, but might affect your programs when running on a big-endian system if they make assumptions about endianness, e.g., by using type casts (or absolute declarations or variant records misused as type casts) in certain ways. Please see the demo program absdemo.pas for an example and how to solve it.

Endianness is also relevant (the more common case) when exchanging data between different machines, e.g. via binary files or over a network. Since the latter is not easily possible in BP, and the techniques to solve the problems are mostly the same as for files, we concentrate on files here.

First, you have to choose the endianness to use for the file. Most known data formats have a specified endianness (usually that of the processor on which the format was originally created). If you define your own binary data format, you're free to choose the endianness to use.

Then, when reading or writing values larger than one byte from/to the file, you have to convert them. GPC's Run Time System supports this by some routines. E.g., you can read an array from a little-endian file with the procedure BlockReadLittleEndian, or write one to a big-endian file with BlockWriteBigEndian. Note: The endianness in the procedure names refers to the file, not the system - the routines know about the endianness of the system they run on, but you have to tell them the endianness of the file to use. This means you do not have to (and must not) use an ifdef to use the version matching the system's endianness.

When reading or writing records or other more complicated structures, either read/write them field by field using BlockReadBigEndian etc., or read/write them with the regular BlockRead and BlockWrite procedures and convert each field after reading or before writing using procedures like ConvertFromBigEndian or ConvertToLittleEndian (but remember, when writing, to undo the conversion afterwards, if you want to keep using the data - this is not necessary with BlockWriteLittleEndian etc.).

Especially for strings, there are ready-made procedures like ReadStringBigEndian or WriteStringLittleEndian which will read/write the length as a 64 bit value (much space for really long strings :-) in the given endianness, followed by the characters (which have no endianness problem).

All these routines are described in detail in the RTS reference (see Run Time System), under endianness. The demo program endiandemo.pas contains an example on how to use these routines.

Node: - -borland-pascal - disable GPC extensions, Next: , Previous: Endianness assumptions, Up: BP Incompatibilities

7.2.12 - -borland-pascal - disable GPC extensions

GPC warns about some BP constructs which are especially "dirty", like misusing typed constants as initialized variables. GPC also supports some features that may conflict with BP code, like macros. The command line option --borland-pascal disables both, so you might want to use it for a first attempt to compile your BP code under GPC. However, we suggest you try compiling without this switch and fixing any resulting problems as soon as you've become acquainted with GPC.

Node: -w - disable all warnings, Next: , Previous: - -borland-pascal - disable GPC extensions, Up: BP Incompatibilities

7.2.13 -w - disable all warnings

Even in --borland-pascal mode, GPC may warn about some dangerous things. To disable all warnings, you can use the -w option (note: lower-case w!). This is not recommended at all, but you may consider it more BP compatible ...

Node: - -uses=System - Swap; HeapError; etc., Next: , Previous: -w - disable all warnings, Up: BP Incompatibilities

7.2.14 - -uses=System - Swap; HeapError; etc.

A few exotic BP routines and declarations (e.g., Swap and HeapError) are contained in a System unit, System, which GPC (unlike BP) does not automatically use in each program. To use it, you can add a uses System; clause to your program. If you don't want to change your code, the command line option --uses=System will do the same.

Node: -D__BP_TYPE_SIZES__ - small integer types etc., Next: , Previous: - -uses=System - Swap; HeapError; etc., Up: BP Incompatibilities

7.2.15 -D__BP_TYPE_SIZES__ - small integer types etc.

Since GPC runs on 32 and 64 bit platforms, integer types have larger sizes than in BP. However, if you use the System unit (see - -uses=System - Swap; HeapError; etc.) and define the symbol __BP_TYPE_SIZES__ (by giving -D__BP_TYPE_SIZES__ on the command line), it will redeclare the types to the sizes used by BP. This is less efficient and more limiting, but might be necessary if your program relies on the exact type sizes.

Node: - -pack-struct - disable structure alignment, Next: , Previous: -D__BP_TYPE_SIZES__ - small integer types etc., Up: BP Incompatibilities

7.2.16 - -pack-struct - disable structure alignment

GPC by default aligns fields of records and arrays suitably for higher performance, while BP doesn't. If you don't want the alignment (e.g., because the program relies on the internal format of your structures), give the --pack-struct option.

Node: -D__BP_RANDOM__ - BP compatible pseudo random number generator, Next: , Previous: - -pack-struct - disable structure alignment, Up: BP Incompatibilities

7.2.17 -D__BP_RANDOM__ - BP compatible pseudo random number generator

GPC uses a more elaborate pseudo random number generator than BP does. Using the Random and Randomize functions works the same way, but there is no RandSeed variable (but a SeedRandom procedure). However, if you use the System unit (see - -uses=System - Swap; HeapError; etc.) and define the symbol __BP_RANDOM__ (by giving -D__BP_RANDOM__ on the command line), it will provide a 100% BP compatible pseudo random number generator, including the RandSeed variable, which will produce exactly the same sequence of pseudo random numbers that BP's pseudo random number generator does. Even the Randomize function will then behave exactly like in BP.

Node: -D__BP_UNPORTABLE_ROUTINES__ - Intr; DosVersion; etc., Next: , Previous: -D__BP_RANDOM__ - BP compatible pseudo random number generator, Up: BP Incompatibilities

7.2.18 -D__BP_UNPORTABLE_ROUTINES__ - Intr; DosVersion; etc.

A few more routines in the Dos and WinDos units besides the ones mentioned under Keep; GetIntVec; SetIntVec, like Intr or DosVersion, are meaningless on non-Dos systems. By default, the Dos unit does not provide these routines (it only provides those that are meaningful on all systems, which are most of its routines, including the most commonly used ones). If you need the unportable ones, you get them by using the System unit (see - -uses=System - Swap; HeapError; etc.) and defining the symbol __BP_UNPORTABLE_ROUTINES__ (by giving -D__BP_UNPORTABLE_ROUTINES__ on the command line). If you use Intr or MsDos, your program will only compile under DJGPP then. Other routines, e.g. DosVersion are emulated quite roughly on other systems. Please see the notes in the Dos unit (see Dos) for details.

Node: -D__BP_PARAMSTR_0__ - BP compatible ParamStr (0) behaviour, Previous: -D__BP_UNPORTABLE_ROUTINES__ - Intr; DosVersion; etc., Up: BP Incompatibilities

7.2.19 -D__BP_PARAMSTR_0__ - BP compatible ParamStr (0) behaviour

In BP (or under Dos), ParamStr (0) always contains the full path of the current executable. Under GPC, by default it contains what was passed by the caller as the 0th argument - which is often the name of the executable, but that's merely a convention, and it usually does not include the path.

If you use the System unit (see - -uses=System - Swap; HeapError; etc.) and define the symbol __BP_PARAMSTR_0__ (by giving -D__BP_PARAMSTR_0__ on the command line), it will change the value of ParamStr (0) to that of ExecutablePath, overwriting the value actually passed by the caller, to imitate BP's/Dos's behaviour. However note: On most systems, ExecutablePath is not guaranteed to return the full path, so defining this symbol doesn't change anything. In general, you cannot expect to find the full executable path, so better don't even try it, or your program will (at best) run on some systems. For most cases where BP programs access their own executable, there are cleaner alternatives available.

Node: IDE versus command line, Next: , Previous: BP Incompatibilities, Up: Borland Pascal

7.3 IDE versus command line

On the Dos (DJGPP) and Linux platforms, you can use RHIDE for GNU Pascal; check the subdirectories of your DJGPP distribution.

Unfortunately, there is no IDE which would run on all platforms. We are working on it, but this will take some time. Please be patient - or offer your help!

Without an IDE, the GNU Pascal Compiler, GPC, is called about like the command-line version of the Borland Pascal Compiler, BPC. Edit your source file(s) with your favorite ASCII editor, then call GNU Pascal with a command line like 

     C:\GNU-PAS> gpc hello.pas -o hello.exe

on your Dos or OS/2 box or 

     myhost:/home/joe/gnu-pascal> gpc hello.pas -o hello

on your Unix (or Unix-compatible) system.

Don't omit the .pas suffix: GPC is a common interface for a Pascal compiler, a C, ObjC and C++ compiler, an assembler, a linker, and perhaps an Ada and a FORTRAN compiler. From the extension of your source file GPC figures out which compiler to run. GPC recognizes Pascal sources by the extension .pas, .p, .pp or .dpr.

The -o is a command line option which tells GPC how the executable has to be named. If not given, the executable will be called a.out (Unix) or a.exe (Dos). However, you can use the --executable-file-name to tell GPC to always call the executable like the source (with the extension removed under Unix and changed to .exe under Dos).

Note that GPC is case-sensitive concerning file names and options, so it will not work if you type 

     C:\GNU-PAS> GPC HELLO.PAS -O HELLO.EXE

GPC is a very quiet compiler and doesn't print anything on the screen unless you request it or there is an error. If you want to see what is going on, invoke GPC with additional options: 

     -Q            "don't be quiet"  (or: Quassel-Modus in German)

(with capital Q!) means that GPC prints out the names of procedures and functions it processes, and 

     --verbose

or abbreviated 

     -v

means that GPC informs you about the stages of compilation, i.e. preprocessing, compiling, assembling, and linking.

One example (this time for OS/2): 

     [C:\GNU-Pascal] gpc --verbose -Q hello.pas

Throughout this chapter, we will tell you about a lot of command-line switches. They are all invoked this way.

After compilation, there will be an executable hello file in the current directory. (hello.exe on Dos or OS/2.) Just run it and enjoy. If you're new to Unix, please note that the current directory is not on the PATH in most installations, so you might have to run your program as ./hello. This also helps to avoid name conflicts with other programs. Such conflicts are especially common with the program name test which happens to be a standard utility under Unix that does not print any output. If you call your program test.pas, compile it, and then invoke test, you will usually not run your program, but the utility which leads to mysterious problems. So, invoke your program as ./test or, better yet, avoid the name test for your programs.

If there are compilation errors, GNU Pascal will not stop compilation after the first one - as Borland Pascal does - but try to catch all errors in one compilation. If you get more error messages than your screen can hold, you can catch them in a file (e.g. gpc.out) or pipe them to a program like more in the following way: 

     gpc hello.pas 2> gpc.out

This works with OS/2 and any bash-like shell under Unix; for Dos you must get a replacement for command.com which supports this kind of redirection, or use the redir utility (see also the DJGPP FAQ, DJGPP FAQ.): 

     C:\GNU-PAS> redir -eo gpc hello.pas -o hello.exe | more

You can also use Borland's IDE for GNU Pascal on the Dos platform: Install the GNU Pascal Compiler in the Tools menu (via Options/Tools). 

     Name:       GNU Pascal
     Path:       gpc
     Arguments:  $SAVE ALL --executable-file-name $NAME($EDNAME).pas
     HotKey:     Shift+F9

Note once more that GPC is case-sensitive, so it is important to specify .pas instead of the .PAS Borland Pascal would append otherwise!

You can include more command-line arguments to GNU Pascal (e.g. --automake; see below) as you will learn more about them.

Since Borland Pascal will try to recompile your program if you use its Run menu function, you will need another tool to run your program: 

     Name:       Run Program
     Path:       command.com
     Arguments:  /c $NAME($EDNAME)
     HotKey:     Shift+F10

Node: Comments, Next: , Previous: IDE versus command line, Up: Borland Pascal

7.4 Comments

GPC supports comments surrounded by { } and (* *), just like BP does. According to the ISO 7185 and ISO 10206 standards, Pascal allows comments opened with (* and closed with }. Borland Pascal does not support such mixed comments, so you might have sources where passages containing comments are "commented out" using the other kind of comment delimiters. GPC's default behaviour is (like BP) not to allow mixed comments, so you don't need to worry about this. However, if you happen to like mixed comments, you can turn them on either by a command-line option, or by a compiler directive: 

     --mixed-comments     {$mixed-comments}    (*$mixed-comments*)

GPC supports nested comments (e.g., { foo { bar } baz }), but they are disabled by default (compatible to BP which doesn't know nested comments at all). You can enable them with the option --nested-comments (or the equivalent compiler directive)

GPC also supports Delphi style comments starting with // and extending until the end of the line. This comment style is activated by default unless one of the --classic-pascal, --extended-pascal, --object-pascal or --borland-pascal dialect options is given. You can turn them on or off with the --[no-]delphi-comments option.

Node: BP Compatible Compiler Directives, Next: , Previous: Comments, Up: Borland Pascal

7.5 BP Compatible Compiler Directives

All of BP's one-letter compiler directives (except H, P, Q, R, V) are supported by GPC, though some of them are ignored because they are not necessary under GPC. Besides, GPC supports a lot more directives. For an overview, see Compiler Directives.

Node: Units; GPI files and Automake, Next: , Previous: BP Compatible Compiler Directives, Up: Borland Pascal

7.6 Units, GPI files and Automake

You can use units in the same way as in Borland Pascal. However, there are some additional features.

Concerning the syntax of a unit, you can, if you want, use Extended Pascal syntax to specify a unit initializer, i.e., instead of writing 

     begin
       ...
     end.

at the end of the unit, you can get the same result with 

     to begin do
       begin
         ...
       end;

and there also exists 

     to end do
       begin
         ...
       end;

which specifies a finalization routine. You can use this instead of Borland Pascal's exit procedures, but for compatibility, the included System unit also provides the ExitProc variable. The to begin do and/or to end do parts must be followed by the final end.. See Modules, for information about Extended Pascal modules, an alternative to units.

When GPC compiles a unit, it produces two files: an .o object file (compatible with other GNU compilers such as GNU C) plus a .gpi file which describes the interface.

If you are interested in the internal format of GPI file, see GPI files.

If you want to compile a program that uses units, you must "make" the project. (This is the command-line switch -M or the IDE keystroke F9 in BP.) For this purpose, GPC provides the command-line switch --automake: 

     gpc --automake hello.pas

If you want to force everything to be rebuilt rather than only recompile changed files (-B or "build" in BP), use --autobuild instead of --automake: 

     gpc --autobuild hello.pas

For more information about the automake mechanism, see Automake.

If you do not want to use the automake mechanism for whatever reason, you can also compile every unit manually and then link everything together.

GPC does not automatically recognize that something is a unit and cannot be linked; you have to tell this by a command line switch: 

     -c            only compile, don't link.

(If you omit this switch when compiling a unit, you only get a linker error message undefined reference to `main'. Nothing serious.)

For example, to compile two units, use: 

     gpc -c myunit1.pas myunit2.pas

When you have compiled all units, you can compile a program that uses them without using --automake: 

     gpc hello.pas

However, using --automake is recommended, since it will recompile units that were modified.

You could also specify the program and the units in one command line: 

     gpc hello.pas myunit1.pas myunit2.pas

One of the purposes of writing units is to compile them separately. However, GNU Pascal allows you to have one or more units in the same source file (producing only one .o file but separate .gpi files). You even can have a program and one or more units in one source file; in this case, no .o file is produced at all.

Node: Optimization, Next: , Previous: Units; GPI files and Automake, Up: Borland Pascal

7.7 Optimization

GNU Pascal is a 32/64 bit compiler with excellent optimization algorithms (which are identically the same as those of GNU C). There are six optimization levels, specified by the command line options -O, -O2, ..., -O6.

One example: 

     program OptimizationDemo;
     
     procedure Foo;
     var
       A, B: Integer;
     begin
       A := 3;
       B := 4;
       WriteLn (A + B)
     end;
     
     begin
       Foo
     end.

When GNU Pascal compiles this program with optimization (-O3), it recognizes that the argument to `WriteLn' is the constant 7 - and optimizes away the variables A and B. If the variables were global, they would not be optimized away because they might be accessed from other places, but the constant 7 would still be optimized.

For more about optimization, see the GNU C documentation.

Node: Debugging, Next: , Previous: Optimization, Up: Borland Pascal

7.8 Debugging

The command line option -g specifies generation of debugging information for GDB, the GNU debugger. GDB comes with its own documentation. Currently, GDB does not understand Pascal syntax, so you should be familiar with C expressions if you want to use it.

See also "Notes for debugging" in the "Programming" chapter; see Notes for Debugging.

Sometimes it is nice to have a look at the assembler output of the compiler. You can do this in a debugger or disassembler (which is the only way to do it in BP), but you can also tell GPC to produce assembler code directly: When you specify the -S command line option, GPC produces an .s file instead of an .o file. The .s file contains assembler source for your program. More about this in the next section.

Node: Objects, Next: , Previous: Debugging, Up: Borland Pascal

7.9 Objects

Objects in the Borland Pascal 7.0 notation are implemented into GNU Pascal with the following differences:

Node: Strings in BP and GPC, Next: , Previous: Objects, Up: Borland Pascal

7.10 Strings in BP and GPC

Strings are "Schema types" in GNU Pascal which is something more advanced than Borland-style strings. For variables, you cannot specify just String as a type like in Borland Pascal; for parameters and pointer types you can. There is no 255 characters length limit. According to Extended Pascal, the maximum string length must be in (parentheses); GNU Pascal accepts [brackets], too, however, like BP.

For more about strings and schema types see Schema Types.

GPC supports Borland Pascal's string handling functions and some more (see String Operations):

Borland Pascal GNU Pascal
Length Length
Pos Pos, Index (1)
Str Str, WriteStr (1) (2)
Val Val, ReadStr (2)
Copy Copy, SubStr, MyStr[2 .. 7] (3)
Insert Insert
Delete Delete
MyStr[0] := #7 SetLength (MyStr, 7)
=, <>, <, <=, >, >= =, <>, <, <=, >, >= (4)
EQ, NE, LT, LE, GT, GE
n/a Trim

Notes:

(1) The order of parameters of the Extended Pascal routines (Index, WriteStr) is different from the Borland Pascal routines.

(2) ReadStr and WriteStr allow an arbitrary number of arguments, and the arguments are not limited to numbers. WriteStr also allows comfortable formatting like WriteLn does, e.g. WriteStr (Dest, Foo : 20, Bar, 1/3 : 10 : 2).

(3) SubStr reports a runtime error if the requested substring does not fit in the given string, Copy does not (like in BP).

(4) By default, the string operators behave like in BP. However, if you use the option --no-exact-compare-strings or --extended-pascal, they ignore differences of trailing blanks, so, e.g., 'foo' and 'foo ' are considered equal. The corresponding functions (EQ, ...) always do exact comparisons.

Node: Typed Constants, Next: , Previous: Strings in BP and GPC, Up: Borland Pascal

7.11 Typed Constants

GNU Pascal supports Borland Pascal's "typed constants" but also Extended Pascal's initialized variables: 

     var
       x: Integer value 7;

or 

     var
       x: Integer = 7;

When a typed constant is misused as an initialized variable, a warning is given unless you specify --borland-pascal.

When you want a local variable to preserve its value, define it as static instead of using a typed constant. Typed constants also become static automatically for Borland Pascal compatibility, but it's better not to rely on this "feature" in new programs. Initialized variables do not become static automatically. 

     program StaticDemo;
     
     procedure Foo;
     { x keeps its value between two calls to this procedure }
     var
       x: Integer = 0; attribute (static);
     begin
       WriteLn (x);
       Inc (x)
     end;
     
     begin
       Foo;
       Foo;
       Foo;
     end.

For records and arrays, GPC supports both BP style and Extended Pascal style initializers. When you initialize a record, you may omit the field names. When you initialize an array, you may provide indices with a :. However, this additional information is ignored completely, so perhaps it's best for the moment to only provide the values ... 

     program BPInitVarDemo;
     const
       A: Integer = 7;
       B: array [1 .. 3] of Char = ('F', 'o', 'o');
       C: array [1 .. 3] of Char = 'Bar';
       Foo: record
         x, y: Integer;
       end = (x: 3; y: 4);
     begin
     end.

Node: Bit; Byte and Memory Manipulation, Next: , Previous: Typed Constants, Up: Borland Pascal

7.12 Bit, Byte and Memory Manipulation

The bitwise operators shl, shr, and, or, xor and not work in GNU Pascal like in Borland Pascal. As an extension, you can use them as procedures, for example 

     program AndProcedureDemo;
     var x: Integer;
     begin
       and (x, $0000ffff);
     end.

as an alternative to 

     program AndOperatorDemo;
     var x: Integer;
     begin
       x := x and $0000ffff;
     end.

GPC accepts the BP style notation $abcd for hexadecimal numbers, but you also can use Extended Pascal notation: 

     program EPBaseDemo;
     const
       Binary =  2#11111111;
       Octal  =  8#177;
       Hex    = 16#ff;
     begin
     end.

and so on up to a basis of 36. Of course, you can mix the notations as you like, e.g.: 

     program BPEPBaseDemo;
     begin
       WriteLn ($cafe = 2#1100101011111110)
     end.

Inc and Dec are implemented like in Borland Pascal. Pred and Succ are generalized according to Extended Pascal and can have a second (optional) parameter: 

     procedure SuccDemo;
     var a: Integer = 42;
     begin
       a := Succ (a, 5);
       WriteLn (a) { 47 }
     end.

BP style absolute variables work in the context of overloading other variables as well as in the context of specifying an absolute address, but the latter is highly unportable and not very useful even in Dos protected mode. 

     program BPAbsoluteDemo;
     
     type
       TString = String (80);
       TTypeChoice = (t_Integer, t_Char, t_String);
     
     { @@ WARNING: BAD STYLE! }
     procedure ReadVar (var x: Void; TypeChoice: TTypeChoice);
     var
       xInt: Integer absolute x;
       xChar: Char absolute x;
       xStr: TString absolute x;
     begin
       case TypeChoice of
         t_Integer: ReadLn (xInt);
         t_Char   : ReadLn (xChar);
         t_String : ReadLn (xStr);
       end
     end;
     
     var
       i: Integer;
       c: Char;
       s: TString;
     
     begin
       ReadVar (i, t_Integer);
       ReadVar (c, t_Char);
       ReadVar (s, t_String);
       WriteLn (i, ' ', c, ' ', s)
     end.

GNU Pascal knows Borland Pascal's procedures FillChar and Move. However, their use can be dangerous because it often makes implicit unportable assumptions about type sizes, endianness, internal structures or similar things. Therefore, avoid them whenever possible. E.g., if you want to clear an array of strings, don't FillChar the whole array with zeros (this would overwrite the Schema discriminants, see Strings), but rather use a for loop to assign the empty string to each string. In fact, this is also more efficient than FillChar, since it only has to set the length field of each string to zero.

Node: User-defined Operators in GPC, Next: , Previous: Bit; Byte and Memory Manipulation, Up: Borland Pascal

7.13 User-defined Operators in GPC

GNU Pascal allows the user to define operators according to the Pascal-SC syntax: 

     program PXSCOperatorDemo;
     
     type
       Point = record
         x, y: Real;
       end;
     
     operator + (a, b: Point) c: Point;
     begin
       c.x := a.x + b.x;
       c.y := a.y + b.y;
     end;
     
     var
       a, b, c: Point = (42, 0.5);
     
     begin
       c := a + b
     end.

The Pascal-SC operators +>, +<, etc. for exact numerical calculations are not implemented, but you can define them.

Node: Data Types in BP and GPC, Next: , Previous: User-defined Operators in GPC, Up: Borland Pascal

7.14 Data Types in BP and GPC

Node: BP Procedural Types, Next: , Previous: Data Types in BP and GPC, Up: Borland Pascal

7.15 BP Procedural Types

In addition to BP's procedural types, GNU Pascal has pointers to procedures: 

     type
       FuncPtr = ^function (Real): Real;

The differences between procedure pointers and procedural types are only syntactical:

One can use both kinds in the same program, of course, though it is recommended to stick to one kind throughout to avoid maximum confusion.

GNU Pascal also supports Standard Pascal's procedural parameters (see Special Parameters).

Furthermore, GNU Pascal allows you to call even local procedures through procedural pointers, variables or parameters without reverting to any dirty tricks (like assembler, which is necessary in BP).

The differences between the various kinds of procedural types, pointers and parameters are demonstrated in the demo program procvardemo.pas. An example for calling local routines through procedural parameters can be found in the demo program iteratordemo.pas.

Node: Files, Next: , Previous: BP Procedural Types, Up: Borland Pascal

7.16 Files

Node: Built-in Constants, Next: , Previous: Files, Up: Borland Pascal

7.17 Built-in Constants

Node: Built-in Operators in BP and GPC, Next: , Previous: Built-in Constants, Up: Borland Pascal

7.18 Built-in Operators in BP and GPC

Besides the operators found in Borland Pascal, GNU Pascal supports the following operators:

Node: Built-in Procedures and Functions, Next: , Previous: Built-in Operators in BP and GPC, Up: Borland Pascal

7.19 Built-in Procedures and Functions

Node: Special Parameters, Next: , Previous: Built-in Procedures and Functions, Up: Borland Pascal

7.20 Special Parameters

Node: Miscellaneous, Next: , Previous: Special Parameters, Up: Borland Pascal

7.21 Miscellaneous

Node: BP and Extended Pascal, Next: , Previous: Miscellaneous, Up: Borland Pascal

7.22 BP and Extended Pascal

Pascal is a well-known programming language and hardly needs to be described here. Note, however, that there is a large difference between the language used by the BP compiler and the Pascal Standards.

Extended Pascal is a standardized language based on the original Standard Pascal, but with significant extensions. Unfortunately, Borland Pascal does not conform to any of the Pascal standards. Writing a program that both complies to Extended Pascal (or even Standard Pascal) and compiles with BP is almost impossible for any non-trivial task.

On the other hand, BP has some nice features that make it very powerful in the environments in which it runs. However, some of those features are of little use on non-Dos systems and would not be good candidates for standardization.

There are also several BP features which are semantically similar to features in Standard Pascal or Extended Pascal, but syntactically different.

Therefore, in order to be useful to users coming from either side, GPC supports both the standards and the BP dialect as good as possible. By default, GPC allows features from any dialect it knows. By giving a dialect option such as --borland-pascal or --extended-pascal, you can tell GPC to disable the features not found in that dialect, and to adjust its warning behaviour to the dialect.

The different sets of reserved words are a little problem, but GPC solves it by making the words in question only "conditionally reserved" which works transparently without problems in most cases. Still, giving a dialect option will disable all keywords not part of this dialect.

Apart from this, there are surprisingly few real conflicts between the dialects. Therefore, you can usually compile your BP code without the --borland-pascal option and make use of all of GPC's features. You might be surprised, though, when GPC accepts things you didn't know were allowed. :-)

Finally, if you want to make use of some of GPC's extensions (compared to BP) and still keep the code compileable with BP without using ifdefs all over the place, we suggest you look at the unit gpc-bp.pas, shipped with GPC, which contains BP versions of some of GPC's features. Please read the comments at the beginning of the unit to find out more about it.

Node: Portability hints, Previous: BP and Extended Pascal, Up: Borland Pascal

7.23 Portability hints

GPC offers you the possibility to make your code fully portable to each of the many platforms supported by GPC. It would be a pity not to make use of this.

This section lists some known pitfalls that often hinder otherwise well-written programs to take full advantage of GPC. If you have never used any compiler but Borland Pascal and similar compilers, some of the advices might look strange to you. But this is just the same level of strangeness that your old programs will have for you once you have understood the principles of cross-platform portability. Remember that many tricks you have always been applying almost automatically in Borland Pascal were necessary to overcome certain limitations of the Dos platform and to compensate for the compiler's missing optimization. Programming with an optimizing compiler like GPC for platforms without a 64 kB limit is a completely new experience - and perhaps it is among the reasons why you are now working with GPC in the first place?

Portability - why?

Okay - but why should I bother and make my program portable? I know that all who want to use my program are running WXYZ-OS anyway.

Yes, but that's the result of a self-fulfilling prophecy. It depends on you whether it will always remain like this or not. Consider a program ABC written for a single platform, WXYZ-OS. Naturally, only WXYZ-OS-users get interested in ABC. The author gets feedback only from WXYZ-OS users and does not see any reason to make the program cross-platform. Then people realize that if they want to run ABC they must move to WXYZ-OS. The author concludes that people only want WXYZ-OS programs, and so on.

To break out, just create a portable version of your program now. Then all OSes have equal chances to show their abilities when running your program, and your customers can choose their OS. Then, maybe, they decide to use your program just for the reason that they can be sure that it will run on all present and future platforms and not only on a specific one - who knows?

My program is a tool specifically designed to make the best of the STUV feature of WXYZ-OS. There is no point in making it portable.

How much do you know about non-WXYZ-OSes? Just ask an expert how the STUV feature is named elsewhere. Be sure, if it is of value, it exists almost everywhere.

Low-level features

I am using a lot of low-level stuff in my programs, so they cannot be portable.

You do not use those low-level routines directly in your high-level routines, do you? There should always be a layer "in-between" that encapsulates the low-level routines and present an API to your program that exactly reflects the needs of your application. This "API in between" is the point where you can exchange the low-level routines by portable calls to GPC's Run Time System.

If you do not have such a layer in-between, then the API of the low-level routines you call are your first approximation for such a layer. If you have ever thought "it would be great if that API function had that additional parameter", then your own extended version of that API function that has that parameter can become part of your "API in between". But then don't stop here: Certainly the API of the OS is not ideal for your program's needs. Just create more routines that encapsulate all OS-specific stuff ...

When the low-level stuff in question consists of interrupts, assembler and similar things, then the first thing you need is a portable replacement of the functionality. Fortunately, GPC covers many things already in Pascal that require assembler in Borland Pascal:

Node: Reference, Next: , Previous: Borland Pascal, Up: Top

8 The Alphabetical GPC Language Reference

This chapter is still under development. All keywords and built-in identifiers are listed, but not all with explanations.

This chapter contains an alphabetical list of all keywords (reserved words) and built-in identifiers of the GNU Pascal compiler. For detailed and comprehensive description of syntax and reserved words, see Programming. This chapter explains only built-in procedures and functions in detail.

It does not cover extensions provided by external units and libraries which are supposed to come with their own documentation. For the interfaces of the units that come with GPC, see GPC Units.

Node: Abs, Next: , Up: Reference

Abs

Synopsis

     function Abs (i: integer_type): integer_type;
or 
     function Abs (x: real_type): real_type;
or 
     function Abs (z: complex_type): real_type;

Description

Returns the absolute value of the argument. For integer or real values of x, the definition is 

     function Abs (x: integer_or_real_type): integer_or_real_type;
     begin
       if x < 0 then
         Abs := -x
       else
         Abs := x
     end;

whereas for complex values it is 

     function Abs (x: Complex): Real;
     begin
       Abs := SqRt (x * Conjugate (x))
     end;

Conforming to

The function Abs is defined in ISO 7185 Pascal; its application to complex values is defined in ISO 10206 Extended Pascal.

Example

     program AbsDemo;
     var
       i1: Complex;
     begin
       WriteLn (Abs (42));             { 42 }
       WriteLn (Abs (-42));            { 42 }
       WriteLn (Abs (-12.1) : 0 : 1);  { 12.1 }
       i1 := Cmplx (1, 1);             { 1 + i }
       WriteLn (Abs (i1) : 0 : 3)      { 1.414, i.e. SqRt (2) }
     end.

See also

Sqr.

Node: absolute, Next: , Previous: Abs, Up: Reference

absolute

Synopsis

     var
       variable_name: data_type absolute variable_reference;
or 
     var
       variable_name: data_type absolute integer_expression;

Description

The first meaning of the absolute directive allows to put a variable to the address of another one and thus provides a type-casting mechanism.

In most cases, variable_reference will be just a variable name, but GPC also allows arbitrary pointer expressions here. If variable_reference has neither a constant address nor is a variable parameter, GPC prints a warning. This warning is suppressed in "extended syntax" mode which is switched on by the --extended-syntax option or the {$X+} compiler directive.

GPC also allows explicit type casts. Variant records (as defined in ISO 7185 Pascal), however, have no guaranteed overlaying and are therefore not suitable for type casts.

The second meaning of absolute places a variable at a specified address. This is useful on machines without virtual memory addressing for doing certain low-level operations, but should be avoided on systems with memory protection such as Unix-like systems. GPC does not check whether the specified virtual address makes any sense and does not provide a built-in mechanism to map it to a real address.

GPC warns about this second use of absolute unless "extended syntax" has been requested.

Conforming to

absolute is a Borland Pascal extension.

Borland Pascal has a slightly different syntax for the second meaning related to the addressing scheme of IA32 processors working in real mode.

Allowing arbitrary memory references instead of just variable names in the first meaning of absolute is a GNU Pascal extension.

Example

     program AbsoluteDemo;
     
     {$X+}
     
     const
       IOMem = $f0000000;
       MaxVarSize = MaxInt div 8;
     
     var
       Mem: array [0 .. MaxVarSize - 1] of Byte absolute 0;
     
       { This address has no actual meaning }
       MyPort: Byte absolute IOMem + $c030;
     
     { Beware: Using any of the variables above will crash
       your program unless you know exactly what you do!
       That's why GPC warns about it without the $X+ directive. }
     
     var
       x: Real;
       a: array [1 .. SizeOf (Real)] of Byte absolute x;
       i: Integer;
       b: Byte absolute a[i];  { GNU Pascal extension:
                                  non-constant memory reference. }
     
     begin
       x := 3.14;
     
       { Look at the internal representation of a real variable. }
       for i := 1 to SizeOf (Real) do
         Write (a[i] : 4);
       WriteLn;
     
       { The same again, more ugly ... }
       for i := 1 to SizeOf (Real) do
         Write (b : 4);
       WriteLn;
     
       { And yes, there's an even more ugly way to do it ... }
       for i := 1 to SizeOf (Real) do
         Write (Mem[PtrCard (@x) + i - 1] : 4);
       WriteLn
     end.

See also

Keywords, record, Type Casts.

Node: abstract, Next: , Previous: absolute, Up: Reference

abstract

Not yet implemented.

Synopsis

Description

Abstract object type or method declaration.

Conforming to

abstract is an Object Pascal extension.

Example

See also

Keywords.

Node: Addr, Next: , Previous: abstract, Up: Reference

Addr

Synopsis

     function Addr (const Foo): Pointer;

Description

Addr returns the address of its argument. It is equivalent to the address operator.

Note: In BP, Addr returns an untyped pointer. GPC does this only with --borland-pascal. Otherwise it returns a typed pointer. Addr never depends on the --[no]-typed-address option/compiler directive, unlike the address operator. (It is recommended you never rely on untyped pointer results, but use a type-cast if really necessary.)

Conforming to

Addr is a Borland Pascal extension.

Example

     program AddrDemo;
     var
       Foo: ^Integer;
       Bar: Integer;
     begin
       Foo := Addr (Bar);  { Let `Foo' point to `Bar'. }
       Bar := 17;
       Foo^ := 42;  { Change the value of `Bar' to 42 }
       WriteLn (Bar)
     end.

See also

Operators.

Node: AlignOf, Next: , Previous: Addr, Up: Reference

AlignOf

Synopsis

     function AlignOf (var x): Integer;

Description

Returns the alignment of a type or variable in bytes.

Conforming to

AlignOf is a GNU Pascal extension.

Example

     program AlignOfDemo;
     var
       a: Integer;
       b: array [1 .. 8] of Char;
     begin
       WriteLn (AlignOf (a));        { Alignment of `Integer'; usually 4 bytes. }
       WriteLn (AlignOf (Integer));  { The same. }
       WriteLn (AlignOf (b));        { Alignment of `Char'; usually 1 byte. }
     end.

Although the array is bigger than a single char, it is accessed char by char, so there usually is no need to align it on a 4 byte boundary or such. (This may be false on some platforms.)

See also

SizeOf, BitSizeOf, TypeOf.

Node: all, Next: , Previous: AlignOf, Up: Reference

all

(Under construction.)

Synopsis

Description

export extension (export foo = all).

Conforming to

all is a GNU Pascal extension.

Example

See also

Keywords.

Node: and, Next: , Previous: all, Up: Reference

and

Synopsis

     operator and (operand1, operand2: Boolean) = Result: Boolean;
or 
     operator and (operand1, operand2: integer_type) = Result: integer_type;
or 
     procedure and (var operand1: integer_type; operand2: integer_type);

Description

In GNU Pascal, and has three built-in meanings:

  1. Logical "and" between two Boolean-type expressions. The result of the operation is of Boolean type.

    By default, and acts as a short-circuit operator in GPC: If the first operand is False, the second operand is not evaluated because the result is already known to be False. You can change this to complete evaluation using the --no-short-circuit command-line option or the {$B+} compiler directive.

  2. Bitwise "and" between two integer-type expressions. The result is of the common integer type of both expressions.
  3. Use as a "procedure": operand1 is "and"ed bitwise with operand2; the result is stored in operand1.

Conforming to

The logical and operator is defined in ISO 7185 Pascal.

According to ISO, you cannot rely on and being a short-circuit operator. On the other hand, GPC's default behaviour does not contradict the ISO standard. (See and_then.) However, since it seems to be a de-facto standard among ISO Pascal compilers to evaluate both operands of and, GPC switches to --no-short-circuit mode if one of the language dialect options selecting ISO Pascal, for instance --extended-pascal, is given. Use --short-circuit to override.

Use of and as a bitwise operator for integers is a Borland Pascal extension.

Use of and as a "procedure" is a GNU Pascal extension.

Example

     program AndDemo;
     var
       a, b, c: Integer;
     begin
       if (a = 0) and (b = 0) then  { logical `and' }
         c := 1
       else if (a and b) = 0 then  { bitwise `and' }
         c := 2
       else
         and (c, a)  { same as `c := c and a' }
     end.

Note the difference between the logical and and the bitwise and: When a is 2 and b is 4, then a and b is 0. Beware: a and b = 0 has nothing to do with (a = 0) and (b = 0)!

Since bitwise and has a higher priority than the = operator, parentheses are needed in if (a = 0) and (b = 0) because otherwise 0 and b would be calculated first, and the remainder would cause a parse error.

See also

Keywords, and_then, and then, or, xor, Operators.

Node: and then, Next: , Previous: and, Up: Reference

and then

Synopsis

     { `and then' is built in. A user-defined operator cannot consist of
        two words. }
     operator and then (operand1, operand2: Boolean) = Result: Boolean;

Description

and then is an alias for the short-circuit logical operator and_then.

Conforming to

While and_then is defined in ISO 10206 Extended Pascal, and then is a GNU Pascal extension.

Example

     program AndThenDemo;
     var
       p: ^Integer;
     begin
       New (p);
       ReadLn (p^);
       if (p <> nil) and then (p^ < 42) then  { This is safe. }
         WriteLn (p^, ' is less than 42')
     end.

See also

Keywords, and_then, and, or else.

Node: and_then, Next: , Previous: and then, Up: Reference

and_then

Synopsis

     operator and_then (operand1, operand2: Boolean) = Result: Boolean;

Description

The and_then short-circuit logical operator performs the same operation as the logical operator and. But while the ISO standard does not specify anything about the evaluation of the operands of and - they may be evaluated in any order, or not at all - and_then has a well-defined behaviour: It evaluates the first operand. If the result is False, and_then returns False without evaluating the second operand. If it is True, the second operand is evaluated and returned.

Since the behaviour described above is the most efficient way to implement and, GPC by default treats and and and_then exactly the same. If you want, for some reason, to have both operands of and evaluated completely, you must assign both to temporary variables and then use and - or and_then, it does not matter.

Conforming to

and_then is an ISO 10206 Extended Pascal extension.

Some people think that the ISO standard requires both operands of and to be evaluated. This is false. What the ISO standard does say is that you cannot rely on a certain order of evaluation of the operands of and; in particular things like the following program can crash according to ISO Pascal, although they cannot crash when compiled with GNU Pascal running in default mode. 

     program AndBug;
     var
       p: ^Integer;
     begin
       New (p);
       ReadLn (p^);
       if (p <> nil) and (p^ < 42) then  { This is NOT safe! }
         WriteLn ('You''re lucky. But the test could have crashed ...')
     end.

Example

     program And_ThenDemo;
     var
       p: ^Integer;
     begin
       New (p);
       ReadLn (p^);
       if (p <> nil) and_then (p^ < 42) then  { This is safe. }
         WriteLn (p^, ' is less than 42')
     end.

See also

Keywords, and then, and, or_else.

Node: AnsiChar, Next: , Previous: and_then, Up: Reference

AnsiChar

Synopsis

     type
       AnsiChar = Char;

Description

AnsiChar is an 8 bit char type. Currently, it is the same as Char, but this might change in the future, once wide chars (16 bit chars) will be introduced into GPC. Depending on the platform, Char might be either AnsiChar or WideChar then.

Conforming to

AnsiChar is a Borland Delphi extension.

Example

     program AnsiCharDemo;
     var
       A: AnsiChar;  { There is nothing special with `AnsiChar'. }
       B: Char;
     begin
       A := 'A';
       A := B
     end.

See also

PAnsiChar, Char.

Node: AnyFile, Next: , Previous: AnsiChar, Up: Reference

AnyFile

Synopsis

     type
       AnyFile  { built-in type }

Description

AnyFile is a built-in type that can only be used for parameters and pointer targets. Any kind of file variable (Text, untyped and typed file) can be passed to such a parameter and their address assigned to such a pointer. On the other side, only generic file operations are possible with AnyFile parameters/pointer targets.

This type is useful for implementing generic file handling routines. Also some built-in file routines use this type for their parameters, e.g. IOSelectRead (see Run Time System).

BlockRead (see BlockRead) and BlockWrite (see BlockWrite) treat AnyFile specially, in that they accept all AnyFiles as arguments (even if the actual file is a typed or Text file) and always use a block size of 1 (even if the actual file is an untyped file with different block size or a typed file of a type with size not equal to one). This is the only way to reliably read/write a certain amount of data from/to an AnyFile.

AnyFile pointers cannot be allocated with New (because it would be unspecified which kind of file to create).

Conforming to

AnyFile is a GNU Pascal extension.

Example

     program AnyFileDemo;
     
     procedure Test (var f: AnyFile);
     var v: ^AnyFile;
     begin
       { Generic file operations are allowed for `AnyFile' }
       Rewrite (f);
     
       { `AnyFile' can also be accessed via pointers }
       v := @f;
       Close (v^)
     end;
     
     var
       t: Text;
       f: file;
       g: file of Integer;
     
     begin
       { Any kind of file variable can be passed as `AnyFile' }
       Test (t);
       Test (f);
       Test (g)
     end.

See also

Text, file.

Node: Append, Next: , Previous: AnyFile, Up: Reference

Append

Synopsis

     procedure Append (var F: any_file; [FileName: String;]
                                         [BlockSize: Cardinal]);

Description

Append opens a file for writing. If the file does not exist, it is created. If it does exist, the file pointer is positioned after the last element.

Like Rewrite, Reset and Extend do, Append accepts an optional second and third parameter for the name of the file in the filesystem and, for untyped files, the block size of the file. (For details, see Rewrite.)

Conforming to

Append, including the BlockSize parameter, is a Borland Pascal extension. ISO 10206 Extended Pascal has Extend instead. The FileName parameter is a GNU Pascal extension.

Example

     program AppendDemo;
     var
       Sample: Text;
     begin
       Assign (Sample, 'sample.txt');
       Rewrite (Sample);
       WriteLn (Sample, 'Hello, World!');  { `sample.txt' now has one line }
       Close (Sample);
     
       { ... }
     
       Append (Sample);
       WriteLn (Sample, 'Hello again!');  { `sample.txt' now has two lines }
       Close (Sample)
     end.

See also

Assign, Reset, Rewrite, Update, Extend.

Node: ArcCos, Next: , Previous: Append, Up: Reference

ArcCos

Synopsis

     function ArcCos (x: Real): Real;
or 
     function ArcCos (z: Complex): Complex;

Description

ArcCos returns the (principal value of the) arcus cosine of the argument. The result is in the range 0 < ArcCos (x) < Pi for real arguments.

Conforming to

ArcCos is a GNU Pascal extension.

Example

     program ArcCosDemo;
     begin
       { yields 3.14159 as ArcCos (0.5) = Pi / 3 }
       WriteLn (3 * ArcCos (0.5) : 0 : 5)
     end.

See also

ArcSin, ArcTan, Sin, Cos, Ln, Arg.

Node: ArcSin, Next: , Previous: ArcCos, Up: Reference

ArcSin

Synopsis

     function ArcSin (x: Real): Real;
or 
     function ArcSin (z: Complex): Complex;

Description

ArcSin returns the (principal value of the) arcus sine of the argument. The result is in the range -Pi / 2 < ArcSin (x) < Pi / 2 for real arguments.

Conforming to

ArcSin is a GNU Pascal extension.

Example

     program ArcSinDemo;
     begin
       { yields 3.14159 as ArcSin (0.5) = Pi / 6 }
       WriteLn (6 * ArcSin (0.5) : 0 : 5)
     end.

See also

ArcCos, ArcTan, Sin, Cos, Ln, Arg.

Node: ArcTan, Next: , Previous: ArcSin, Up: Reference

ArcTan

Synopsis

     function ArcTan (x: Real): Real;
or 
     function ArcTan (z: Complex): Complex;

Description

ArcTan returns the (principal value of the) arcus tangent of the argument. The result is in the range -Pi / 2 < ArcTan (x) < Pi / 2 for real arguments.

Conforming to

ArcTan is defined in ISO 7185 Pascal; its application to complex values is defined in ISO 10206 Extended Pascal.

Example

     program ArcTanDemo;
     begin
       { yields 3.14159 as ArcTan (1) = Pi / 4 }
       WriteLn (4 * ArcTan (1) : 0 : 5)
     end.

See also

ArcSin, ArcCos, Sin, Cos, Ln, Arg.

Node: Arg, Next: , Previous: ArcTan, Up: Reference

Arg

Synopsis

     function Arg (z: Complex): Real;

Description

Arg returns the complex "argument", i.e. the angle (in radian) in the complex plane with respect to the real axis, of its parameter z. The result is in the range of -Pi < Arg (z) <= Pi.

Conforming to

Arg is an ISO 10206 Extended Pascal extension.

Example

     program ArgDemo;
     var
       z: Complex;
     begin
       z := Cmplx (1, 1);  { 1 + i }
       WriteLn (Arg (z) : 0 : 5)  { yields 0.78540, i.e. Pi / 4 }
     end.

See also

ArcTan, Ln, Polar.

Node: array, Next: , Previous: Arg, Up: Reference

array

Synopsis

In type definitions: 

     array [index_type] of element_type
or 
     array [index_type, ..., index_type] of element_type

In parameter list declarations: 

     array of element_type

Description

The reserved word array is used to define an array type.

@@conformant/open arrays

Conforming to

Array types are defined in ISO 7185 Pascal.

Example

     program ArrayDemo;
     type
       IntArray = array [1 .. 20] of Integer;
       WeekDayChars = array [(Mon, Tue, Wed, Thu, Fri, Sat, Sun)] of Char;
       Foo = array [0 .. 9, 'a' .. 'z', (Baz, Glork1, Fred)] of Real;
       TwoDimIntArray = array [1 .. 10] of IntArray;
       { is equivalent to: }
       TwoDimIntArray2 = array [1 .. 10, 1 .. 20] of Integer;
     
     procedure PrintChars (F: array of Char);
     var
       i: Integer;
     begin
       for i := Low (F) to High (F) do
         WriteLn (F[i])
     end;
     
     var
       Waldo: WeekDayChars;
     
     begin
       Waldo := 'HiWorld';
       PrintChars (Waldo)
     end.

See also

Keywords, Array Types, High, Low

Node: as, Next: , Previous: array, Up: Reference

as

(Under construction.)

Synopsis

Description

Object type membership test and conversion.

Conforming to

as is an Object Pascal and a Borland Delphi extension.

Example

See also

Keywords, is, TypeOf, OOP.

Node: asm, Next: , Previous: as, Up: Reference

asm

(Under construction.)

Synopsis

Description

See http://www.gnu-pascal.de/contrib/misc/gpcasm.zip.

Conforming to

asm, as implemented in GPC, is a GNU Pascal extension. It is mostly compatible to GCC's asm, but not compatible to that of Borland Pascal.

Example

See also

Keywords.

Node: asmname, Next: , Previous: asm, Up: Reference

asmname

Synopsis

Description

Deprecated! Use external name now.

Conforming to

Example

See also

Keywords, external, name, Importing Libraries from Other Languages.

Node: Assert, Next: , Previous: asmname, Up: Reference

Assert

Synopsis

     procedure Assert (Condition: Boolean);
or 
     procedure Assert (Condition: Boolean; const Message: String);

Description

Assert checks the given Condition at run-time. If it is true, it does nothing. If it is false, it raises a runtime error, using the second argument for the message if given.

However, if the switch --no-assertions is given (see GPC Command Line Options), Assert is deactivated. It still evaluates the condition if it has side effects, but never raises a runtime error.

Conforming to

Assert is a Borland Delphi extension.

Example

See also

CompilerAssert.

Node: Assign, Next: , Previous: Assert, Up: Reference

Assign

(Under contruction.)

Synopsis

     procedure Assign (var F: any_file; FileName: String);

Description

Conforming to

Assign is a Borland Pascal extension.

Example

See also

Reset, Rewrite, Update, Extend, Append.

Node: Assigned, Next: , Previous: Assign, Up: Reference

Assigned

(Under construction.)

Synopsis

     function Assigned (p: Pointer): Boolean;
or 
     function Assigned (p: procedural_type): Boolean;

Description

The Assigned function returns True if the pointer parameter or the address of the procedural parameter is not nil; it returns False if it is nil.

Conforming to

Assigned is a Borland Pascal extension.

Example

     program AssignedDemo;
     type
       PInt = ^Integer;
     
     procedure TellIfOdd (p: PInt);
     begin
       if Assigned (p) and then Odd (p^) then
         WriteLn ('The pointer p points to an odd value.')
     end;
     
     var
       foo: Integer;
     begin
       TellIfOdd (nil);
       foo := 1;
       TellIfOdd (@foo);
       foo := 2;
       TellIfOdd (@foo)
     end.

See also

Null, nil, Pointer.

Node: attribute, Next: , Previous: Assigned, Up: Reference

attribute

(Under construction.)

Synopsis

     declaration attribute (name);

or 

     declaration attribute (name = parameter);

or 

     declaration attribute (name (parameter, parameter ...));

Description

Several attributes can be given in one attribute directive, separated with ,, or in several attribute directives.

Besides the attributes that GCC supports (see Attribute Syntax), GPC allows the following attributes for variables:

For routines it allows the following additional attributes:

For types it allows the following additional attributes:

Size can be applied to integer and Boolean types to produce types with a specified size in bits; for example 

     type
       Card16 = Cardinal attribute (Size = 16);

defines an unsigned integer type with 16 bits.

Variable and routine attributes are preceded by a ;, type attributes are not. So, e.g., in the following example, the Size attribute applies to the type, and the static attribute to the variable. 

     var a: Integer attribute (Size = 64); attribute (static);

Conforming to

attribute is a GNU Pascal extension.

Example

     program AttributeDemo;
     
     { Demo for `iocritical' attribute. }
     
     { Program will abort with a runtime error! }
     
     {$I-}
     procedure p; attribute (iocritical);
     var t: Text;
     begin
       Reset (t)  { Will not cause a runtime error here because I/O
                    checking is off, but leave InOutRes set. }
     end;
     {$I+}
     
     begin
     
       p;
       { Since `p' was declared `iocritical', and I/O checking is now on,
         InOutRes is checked immediately after the call to p, and a
         runtime error raised. }
     
       { So this statement is never reached. }
       InOutRes := 0;
     
       { Neither this one, which would be reached without the
         `iocritical' attribute. }
       WriteLn ('never gets here')
     
     end.

See also

Keywords, external.

Node: begin, Next: , Previous: attribute, Up: Reference

begin

Synopsis

     begin
       statement;
       statement;
       ...
       statement
     end;

Description

The reserved word begin opens a begin ... end statement which joins several statements to one compound statement.

Conforming to

begin is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program BeginDemo;
     begin
       if True then
         WriteLn ('single statement');
       if True then
         begin                     { clamp statement1 ... }
           WriteLn ('statement1');
           WriteLn ('statement2')
         end                       { ... to statement2 }
     end.

See also

Keywords, begin end Compound Statement, end

Node: Bind, Next: , Previous: begin, Up: Reference

Bind

(Under construction.)

Synopsis

     procedure Bind (var F: any_file; B: BindingType);

Description

Conforming to

Bind is an ISO 10206 Extended Pascal extension.

Example

See also

Unbind, Binding, BindingType, bindable.

Node: bindable, Next: , Previous: Bind, Up: Reference

bindable

(Under construction.)

Synopsis

Description

External bindability of files.

Conforming to

bindable is an ISO 10206 Extended Pascal extension.

Example

See also

Keywords, Bind, Unbind, Binding, BindingType.

Node: Binding, Next: , Previous: bindable, Up: Reference

Binding

(Under construction.)

Synopsis

     function Binding (F: any_file): BindingType;

Description

Conforming to

Binding is an ISO 10206 Extended Pascal extension.

Example

See also

Bind, Unbind, BindingType, bindable.

Node: BindingType, Next: , Previous: Binding, Up: Reference

BindingType

(Under construction.)

Synopsis

     type
       UnixTimeType = LongInt;
       BindingType = {@@packed} record
         Bound           : Boolean;
         Force           : Boolean;      { Can be set to allow binding to
                                           directories or inaccessible files }
         Extensions_Valid: Boolean;
         Readable        : Boolean;
         Writable        : Boolean;
         Executable      : Boolean;
         Existing        : Boolean;      { Binding points to an existing file }
         Directory       : Boolean;      { Binding points to an existing
                                           directory; Existing is False then }
         Special         : Boolean;      { Binding points to an existing
                                           special file (device, pipe, socket,
                                           etc.); Existing is False then }
         SymLink         : Boolean;      { Binding points to a symbolic link }
         AccessTime,                     { Time of last access }
         ModificationTime,               { Time of last modification }
         ChangeTime      : UnixTimeType; { Time of last change }
         User,                           { User ID of owner }
         Group,                          { Group ID of owner }
         Mode,                           { Access permissions, cf. ChMod }
         Device,                         { Device the file is on }
         INode           : Integer;      { Unix INode number }
         TextBinary      : Boolean;      { Open a Text file in binary mode }
         Handle          : Integer;      { Can be set to bind a Pascal file to
                                           a given file handle }
         CloseFlag       : Boolean;      { If Handle is used, tell whether to
                                           close it when file is closed }
         Name            : String (Binding_Name_Length)
       end;

(@@ Currently, in GPC, BindingType is not actually packed.)

The fields Bound and Name are required by Extended Pascal.

Binding_Name_Length is an implementation-defined constant.

Description

Conforming to

BindingType is an ISO 10206 Extended Pascal extension.

Example

See also

Bind, Unbind, Binding, bindable.

Node: BitSizeOf, Next: , Previous: BindingType, Up: Reference

BitSizeOf

Synopsis

     function BitSizeOf (var x): SizeType;

Description

Returns the size of a type or variable in bits.

Conforming to

BitSizeOf is a GNU Pascal extension.

Example

     program BitSizeOfDemo;
     type
       Int12 = Integer attribute (Size = 12);
     var
       a: Integer;
       b: array [1 .. 8] of Char;
       c: Int12;
       d: packed record
            x: Int12;
            y: 0 .. 3
          end;
     begin
       WriteLn (BitSizeOf (a));    { Size of an `Integer'; usually 32 bits. }
       WriteLn (BitSizeOf (Integer));  { The same. }
       WriteLn (BitSizeOf (b));    { Size of eight `Char's; usually 64 bits. }
       WriteLn (BitSizeOf (c));    { e.g. 16 bits (smallest addressable space). }
       WriteLn (BitSizeOf (d));    { e.g. 16 }
       WriteLn (BitSizeOf (d.x));  { 12 }
       WriteLn (BitSizeOf (d.y))   { 2 }
     end.

See also

SizeOf, AlignOf, TypeOf.

Node: BlockRead, Next: , Previous: BitSizeOf, Up: Reference

BlockRead

(Under construction.)

Synopsis

     procedure BlockRead (var F: File; var Buffer; Blocks: Integer);
or 
     procedure BlockRead (var F: File; var Buffer; Blocks: Integer;
                          var BlocksRead: Integer);

Description

Conforming to

BlockRead is a UCSD Pascal extension.

Example

See also

Node: BlockWrite, Next: , Previous: BlockRead, Up: Reference

BlockWrite

(Under construction.)

Synopsis

     procedure BlockWrite (var F: File; const Buffer; Blocks: Integer);
or 
     procedure BlockWrite (var F: File; const Buffer; Blocks: Integer;
                           var BlocksWritten: Integer);

Description

Conforming to

BlockWrite is a UCSD Pascal extension.

Example

See also

Node: Boolean, Next: , Previous: BlockWrite, Up: Reference

Boolean

Synopsis

     type
       Boolean = (False, True); { built-in type }

Description

The intrinsic Boolean represents boolean values, i.e. it can only assume the two values True and False (which are predefined constants).

Conforming to

Boolean is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program BooleanDemo;
     var
       a: Boolean;
     begin
       a := True;
       WriteLn (a)
     end.

See also

Boolean (Intrinsic), True, False, CBoolean, ByteBool, ShortBool, MedBool, WordBool, LongBool, LongestBool.

Node: Break, Next: , Previous: Boolean, Up: Reference

Break

Synopsis

     Break  { simple statement }

Description

With Break you can exit the body of the current loop instantly. It can only be used within a while, repeat or a for statement.

Conforming to

Break is a Borland Pascal extension.

Example

     program BreakDemo;
     var
       Foo: Integer;
     begin
       while True do
         begin
           repeat
             WriteLn ('Enter a number less than 100:');
             ReadLn (Foo);
             if Foo < 100 then
               Break;  { Exits `repeat' loop }
             WriteLn (Foo, ' is not exactly less than 100! Try again ...')
           until False;
           if Foo > 50 then
             Break;  { Exits `while' loop }
           WriteLn ('The number entered was not greater than 50.')
         end
     end.

See also

Loop Control Statements, Continue, Exit, Halt, Return, goto.

Node: Byte, Next: , Previous: Break, Up: Reference

Byte

Synopsis

     type
       Byte  { built-in type }

Description

Byte is an unsigned integer type which is one "unit" wide. On most platforms one unit has 8 bits, therefore the type is named "byte" and usually has a range of 0..255. (It is the same as ByteCard.)

Byte in GNU Pascal is compatible to unsigned char in GNU C.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

Byte is a Borland Pascal extension. (For something equivalent in ISO Pascal, see Subrange Types.)

Example

     program ByteDemo;
     var
       a: Byte;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: ByteBool, Next: , Previous: Byte, Up: Reference

ByteBool

Synopsis

     type
       ByteBool = Boolean attribute (Size = BitSizeOf (Byte)); { built-in type }

Description

The intrinsic ByteBool represents boolean values, but occupies the same memory space as a Byte. It is used when you need to define a parameter or record that conforms to some external library or system specification.

Conforming to

ByteBool is a Borland Pascal extension.

Example

     program ByteBoolDemo;
     var
       a: ByteBool;
     begin
       Byte (a) := 1;
       if a then WriteLn ('Ord (True) = 1')
     end.

See also

Boolean (Intrinsic), Boolean, True, False, CBoolean, ShortBool, MedBool, WordBool, LongBool, LongestBool.

Node: ByteCard, Next: , Previous: ByteBool, Up: Reference

ByteCard

Synopsis

     type
       ByteCard = Cardinal attribute (Size = BitSizeOf (Byte));

Description

ByteCard is an unsigned integer type which is one "unit" wide. On most platforms one unit has 8 bits, therefore the type is prefixed "byte-" and usually has a range of 0..255.

ByteCard in GNU Pascal is compatible to unsigned char in GNU C.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

ByteCard is a GNU Pascal extension.

Example

     program ByteCardDemo;
     var
       a: ByteCard;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: ByteInt, Next: , Previous: ByteCard, Up: Reference

ByteInt

Synopsis

     type
       ByteInt = Integer attribute (Size = BitSizeOf (Byte));

Description

ByteInt is a signed integer type which is one "unit" wide. On most platforms one unit has 8 bits, therefore the type is prefixed "byte-" and usually has a range of -128..127.

ByteInt in GNU Pascal is compatible to signed char in GNU C.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

ByteInt is a GNU Pascal extension.

ByteInt in GNU Pascal corresponds to ShortInt in Borland Pascal.

Example

     program ByteIntDemo;
     var
       a: ByteInt;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: c, Next: , Previous: ByteInt, Up: Reference

c

Synopsis

Description

Deprecated! Use external now.

Conforming to

Example

See also

Keywords, Importing Libraries from Other Languages, external.

Node: Card, Next: , Previous: c, Up: Reference

Card

Synopsis

     function Card (S: any_set): Integer;

Description

The function Card (S) returns the number of elements in the set S.

Conforming to

Card is an ISO 10206 Extended Pascal extension.

Example

     program CardDemo;
     var
       Foo: set of 1 .. 100;
     begin
       Foo := [1, 2, 3, 5, 1, 1, 1, 2, 2, 2, 3, 3, 5, 5];  { four elements }
       WriteLn ('foo consists of ', Card (Foo), ' elements')
     end.

See also

set

Node: Cardinal, Next: , Previous: Card, Up: Reference

Cardinal

Synopsis

     type
       Cardinal  { built-in type }

Description

Cardinal is the "natural" unsigned integer type in GNU Pascal. On most platforms it is 32 bits wide and thus has a range of 0..4294967295. Use it whenever you need a general-purpose unsigned integer type and don't need to care about compatibility to other Pascal dialects.

Cardinal in GNU Pascal is compatible to unsigned int in GNU C.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

Cardinal is not defined in ISO Pascal, but several Pascal compilers support it as an extension. In Borland Delphi, for instance, it is an unsigned 16-bit in version 1.0, an unsigned 31-bit integer from version 2.0 on, and an unsigned 32-bit integer from version 4.0 on.

Example

     program CardinalDemo;
     var
       a: Cardinal;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: case, Next: , Previous: Cardinal, Up: Reference

case

Synopsis

     case expression of
       selector: statement;
       ...
       selector: statement;
     end;
or, with alternative statement sequence: 
     case expression of
       selector: statement;
       ...
       selector: statement;
     otherwise  { ``else'' instead of ``otherwise'' is allowed }
       statement;
       ...
       statement;
     end;
or, as part of the invariant record type definition: 
     foo = record
       field_declarations
     case bar: variant_type of
       selector: (field_declarations);
       selector: (field_declarations);
       ...
     end;
or, without a variant selector field, 
     foo = record
       field_declarations
     case variant_type of
       selector: (field_declarations);
       selector: (field_declarations);
       ...
     end;

Description

case opens a case statement. For further description see case Statement.

For case in a variant record type definition, see Record Types.

Conforming to

The case statement is defined in ISO 7185 Pascal and supported by all known Pascal variants.

According to ISO 7185 Pascal, the selector type must be a named type. UCSD Pascal and Borland Pascal allow any ordinal type here.

The alternative statement execution with otherwise it is an Extended Pascal extension; with else it is a Borland Pascal extension. In GNU Pascal, both are allowed.

Example

     program CaseDemo;
     var
       Foo: String (10);
       Bar: Integer;
     begin
       WriteLn ('Enter up to ten arbitrary characters:');
       ReadLn (Foo);
       for Bar := 1 to Length (Foo) do
         begin
           Write (Foo[Bar], ' is ');
           case Foo[Bar] of
             'A' .. 'Z', 'a' .. 'z':
               WriteLn ('an English letter');
             '0' .. '9':
               WriteLn ('a number');
           otherwise
             WriteLn ('an unrecognized character')
           end
         end
     end.

See also

Keywords, if Statement, Record Types, else, otherwise

Node: CBoolean, Next: , Previous: case, Up: Reference

CBoolean

(Under construction.)

Synopsis

     type
       CBoolean  { built-in type }

Description

CBoolean is a Boolean type. In GNU Pascal it is compatible to _Bool in GNU C (which is defined as bool in stdbool.h). This compatibility is the reason why CBoolean exists.

Conforming to

CBoolean is a GNU Pascal extension.

Example

     program CBooleanDemo;
     var
       a: CBoolean;
     begin
       a := True;
       if Ord (a) = 1 then WriteLn ('Ord (True) = 1')
     end.

See also

Boolean (Intrinsic), Integer Types, Boolean, True, False, ByteBool, ShortBool, MedBool, WordBool, LongBool, LongestBool.

Node: Char, Next: , Previous: CBoolean, Up: Reference

Char

Synopsis

     type
       Char  { built-in type }

Description

The built-in type Char holds elements of the operating system's character set (usually ASCII). The Char type is a special case of ordinal type. Conversion between character types and ordinal types is possible with the built-in functions Ord and Chr.

Conforming to

Char is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program CharDemo;
     var
       a: Char;
     begin
       a := 'x';
       WriteLn (a)
     end.

See also

Character Types, Ordinal Types, Type Casts, Ord, Chr.

Node: ChDir, Next: , Previous: Char, Up: Reference

ChDir

Synopsis

     procedure ChDir (Directory: String);

Description

ChDir changes the current directory to Directory, if its argument is a valid parameter to the related operating system's function. Otherwise, a runtime error is caused.

Conforming to

ChDir is a Borland Pascal extension.

Example

     program ChDirDemo;
     var
       Foo: String (127);
     begin
       WriteLn ('Enter directory name to change to:');
       ReadLn (Foo);
       {$I-}  { Don't abort the program on error }
       ChDir (Foo);
       if IOResult <> 0 then
         WriteLn ('Cannot change to directory `', Foo, '''.')
       else
         WriteLn ('Okay.')
     end.

See also

MkDir, RmDir

Node: Chr, Next: , Previous: ChDir, Up: Reference

Chr

Synopsis

     function Chr (AsciiCode: Integer): Char;

Description

Chr returns a character whose ASCII code corresponds to the value given by AsciiCode.

Conforming to

Chr is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program ChrDemo;
     var
       x: Integer;
     begin
       for x := 32 to 122 do
         Write (Chr (x))
     end.

See also

Character Types, Ord, Char

Node: c_language, Next: , Previous: Chr, Up: Reference

c_language

Synopsis

Description

Deprecated! Use external now.

Conforming to

Example

See also

Keywords, Importing Libraries from Other Languages, external.

Node: class, Next: , Previous: c_language, Up: Reference

class

Not yet implemented.

Synopsis

Description

OOE/Delphi style object class.

Conforming to

class is an Object Pascal and a Borland Delphi extension.

Example

See also

Keywords.

Node: Close, Next: , Previous: class, Up: Reference

Close

(Under construction.)

Synopsis

     procedure Close (var F: any_file);

Description

Conforming to

Close is a UCSD Pascal extension.

Example

See also

Node: Cmplx, Next: , Previous: Close, Up: Reference

Cmplx

Synopsis

     function Cmplx (RealPart, ImaginaryPart: Real): Complex;

Description

Cmplx makes a complex number from RealPart and ImaginaryPart.

Conforming to

Cmplx is an ISO 10206 Extended Pascal extension.

Example

     program CmplxDemo;
     var
       z: Complex;
       x, y: Real;
     begin
       z := Cmplx (x, y)  { z := x + iy }
     end.

See also

Re, Im, Polar, Arg

Node: Comp, Next: , Previous: Cmplx, Up: Reference

Comp

Synopsis

     type
       Comp = LongInt;

Description

Comp is a signed integer type which is longer than Integer. On most platforms it is 64 bits wide and thus has a range of -9223372036854775808..9223372036854775807.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

Comp is a Borland Pascal extension.

In some contexts, Borland Pascal treats Comp as a "real" type - this behaviour is not supported by GPC.

Example

     program CompDemo;
     var
       a: Comp;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: CompilerAssert, Next: , Previous: Comp, Up: Reference

CompilerAssert

Synopsis

     procedure CompilerAssert (Condition: Boolean);
or 
     function CompilerAssert (Condition: Boolean): Boolean;
or 
     function CompilerAssert (Condition: Boolean;
                ResultValue: Any_Type): type of ResultValue;

Description

CompilerAssert checks the given Condition at compile-time. If it is a compile-time constant of Boolean type with the value True, it returns ResultValue, or if called with only one argument, it returns True or nothing if used as a procedure.

If Condition cannot be evaluated at compile-time or does not have the value True, it causes a compile-time error.

So it can be used to make sure that certain assumptions hold before relying on them.

CompilerAssert does not depend on the --[no-]assertions options. It does not generate any run-time code.

Conforming to

CompilerAssert is a GNU Pascal extension.

Example

     program CompilerAssertDemo;
     
     var
       a: LongInt;
     
     const
       { Make sure that the highest value a can hold is larger than
         MaxInt, and set b to that value. }
       b = CompilerAssert (High (a) > MaxInt, High (a));
     
       { Do a similar check for the minimum value, setting c to True
         (which can be ignored). }
       c = CompilerAssert (Low (a) < Low (Integer));
     
     begin
       { Procedure-like use of CompilerAssert in the statement part. }
       CompilerAssert (MaxInt >= 100000);
     
       WriteLn (b, ' ', c)
     end.

See also

Assert.

Node: Complex, Next: , Previous: CompilerAssert, Up: Reference

Complex

(Under construction.)

Synopsis

     type
       Internal_Complex = record  { not visible }
         RealPart, ImaginaryPart: Real
       end;
       Complex = restricted Internal_Complex;

Description

Conforming to

Complex is an ISO 10206 Extended Pascal extension.

Example

     program ComplexDemo;
     var
       a: Complex;
     begin
       a := Cmplx (42, 3);
       WriteLn (Re (a), ' + ', Im (a), ' i')
     end.

See also

Node: Concat, Next: , Previous: Complex, Up: Reference

Concat

(Under construction.)

Synopsis

     function Concat (S1, S2: String): String;
or 
     function Concat (S1, S2, S3: String): String;
or 
     ...

Description

Conforming to

Concat is a UCSD Pascal extension.

Example

See also

Node: Conjugate, Next: , Previous: Concat, Up: Reference

Conjugate

Synopsis

     function Conjugate (z: Complex): Complex;

Description

Conjugate computes the complex conjugate of the complex number z

Conforming to

Conjugate is a GNU Pascal extension.

Example

     program ConjugateDemo;
     var
       z: Complex;
     begin
       z := Cmplx (2, 3);  { z is 2 + i * 3 }
       WriteLn ('z = ', Re (z) : 0 : 5, ' + i * ', Im (z) : 0 : 5);
       z := Conjugate (z);  { z conjugate is 2 - i * 3 }
       WriteLn ('z conjugate = ', Re (z) : 0 : 5,' + i * ', Im (z) : 0 : 5)
     end.

See also

Cmplx, Re, Im, Abs

Node: const, Next: , Previous: Conjugate, Up: Reference

const

(Under construction.)

Synopsis

Description

Constant declaration or constant parameter declaration.

Conforming to

const is defined in ISO 7185 Pascal and supported by all known Pascal variants. const parameters are a Borland Pascal extension. Pointers to const are a GNU Pascal extension.

Constant declarations allow you to define names for constant (unchanging) values, such as using SecondsPerHour instead of 3600. This can make your program much more readable and maintainable.

GNU Pascal allows you to define constant strings, records and arrays as well as simple numeric constants.

GNU Pascal also implements the const parameter extension which allows the compiler to pass parameters by reference while still allowing you to pass constant values as inputs. See Subroutine Parameter List Declaration for more information.

@@ Pointers to const @@

Example

     program ConstDemo;
     
     type
       Rec = record
         x: Integer;
         y: Integer;
       end;
     
     const
       a = 5;
       constr: Rec = (10, 12);
     
     procedure doit (const r: Rec; const s: String);
     begin
       WriteLn (r.x);
       WriteLn (r.y);
       WriteLn (s);
     end;
     
     var
       variabler: Rec;
     
     begin
       variabler.x := 16;
       variabler.y := 7;
       doit (variabler, 'Should be 16 and 7');
       doit (constr, 'Should be 10 and 12');
     end.

See also

Keywords, var, protected, Subroutine Parameter List Declaration.

Node: constructor, Next: , Previous: const, Up: Reference

constructor

(Under construction.) ;-)

Synopsis

Description

Object constructor.

Conforming to

constructor is an Object Pascal and a Borland Pascal extension.

Example

See also

Keywords.

Node: Continue, Next: , Previous: constructor, Up: Reference

Continue

Synopsis

     Continue  { simple statement }

Description

Continue goes on with loop iteration by jumping to the end of the current loop body. Note: Continue can only stand within a while, repeat or a for statement.

Conforming to

Continue is a Borland Pascal extension.

Example

     program ContinueDemo;
     var
       Foo, Bar: Integer;
     begin
       WriteLn ('Enter three numbers:');
       for Bar := 1 to 3 do
         begin
           ReadLn (Foo);
           if Foo < 5 then
             Continue;
           WriteLn ('Your number was greater than 5.')
         end
     end.

See also

Loop Control Statements, Break, Exit, Halt, Return, goto.

Node: Copy, Next: , Previous: Continue, Up: Reference

Copy

Synopsis

     function Copy (S: String; FirstChar, Count: Integer): String;
or 
     function Copy (S: String; FirstChar: Integer): String;

Description

Copy returns a sub-string of S starting with the character at position FirstChar. If Count is given, such many characters will be copied into the sub-string. If Count is omitted, the sub-string will range to the end of S.

If Count is too large for the sub-string to fit in S, the result will be truncated at the end of S. If FirstChar exceeds the length of S, the empty string will be returned. (For a function which does not truncate but triggers a runtime error instead, see SubStr.)

Please note that GPC's strings may be longer than 255 characters. If you want to isolate the second half of a string S starting with the third character, use Copy (S, 3) instead of Copy (S, 3, 255).

Conforming to

Copy is a UCSD Pascal extension. The possibility to omit the third parameter is a GNU Pascal extension.

Example

     program CopyDemo;
     var
       S: String (42);
     begin
       S := 'Hello';
       WriteLn (Copy (S, 2, 3));  { yields `ell' }
       WriteLn (Copy (S, 3));     { yields `llo' }
       WriteLn (Copy (S, 4, 7));  { yields `lo' }
       WriteLn (Copy (S, 42))     { yields the empty string }
     end.

See also

SubStr, String Slice Access.

Node: Cos, Next: , Previous: Copy, Up: Reference

Cos

Synopsis

     function Cos (x: Real): Real;
or 
     function Cos (z: Complex): Complex;

Description

Cos returns the cosine of the argument. The result is in the range -1 < Cos (x) < 1 for real arguments.

Conforming to

The function Cos is defined in ISO 7185 Pascal; its application to complex values is defined in ISO 10206 Extended Pascal.

Example

     program CosDemo;
     begin
       { yields 0.5 since Cos (Pi / 3) = 0.5 }
       WriteLn (Cos (Pi / 3) : 0 : 5)
     end.

See also

ArcTan, Sin, Ln, Arg.

Node: CString, Next: , Previous: Cos, Up: Reference

CString

(Under construction.)

Synopsis

     type
       CString = ^Char;

Description

Conforming to

CString is a GNU Pascal extension.

Example

     program CStringDemo;
     var
       s: CString;
     begin
       s := 'Hello, world!';
       {$X+}
       WriteLn (s)
     end.

See also

Node: CString2String, Next: , Previous: CString, Up: Reference

CString2String

(Under construction.)

Synopsis

     function CString2String (S: CString): String;

Description

Conforming to

CString2String is a GNU Pascal extension.

Example

See also

Node: CStringCopyString, Next: , Previous: CString2String, Up: Reference

CStringCopyString

(Under construction.)

Synopsis

     function CStringCopyString (Dest: CString; const Source: String): CString;

Description

Conforming to

CStringCopyString is a GNU Pascal extension.

Example

See also

Node: CurrentRoutineName, Next: , Previous: CStringCopyString, Up: Reference

CurrentRoutineName

Synopsis

     function CurrentRoutineName: String;

Description

CurrentRoutineName returns the name of the current routine from where it's called.

Conforming to

CurrentRoutineName is a GNU Pascal extension.

Example

     program CurrentRoutineNameDemo;
     
     procedure FooBar;
     begin
       WriteLn (CurrentRoutineName)  { `FooBar' }
     end;
     
     begin
       WriteLn (CurrentRoutineName);  { `main program' }
       FooBar
     end.

See also

Node: Date, Next: , Previous: CurrentRoutineName, Up: Reference

Date

Synopsis

     function Date (T: TimeStamp): packed array [1 .. Date_length] of Char;

Description

Date takes a TimeStamp parameter and returns the date as a string (in the form of a packed array of Char). Date_length is an implementation defined invisible constant.

Conforming to

Date is an ISO 10206 Extended Pascal extension.

Example

Set TimeStamp.

See also

TimeStamp, GetTimeStamp, Time, Date And Time Routines.

Node: Dec, Next: , Previous: Date, Up: Reference

Dec

Synopsis

For ordinal types: 

     procedure Dec (var x: ordinal_type);
or 
     procedure Dec (var x: ordinal_type; Amount: Integer);

For pointer types: 

     procedure Dec (var p: any_pointer_type);
or 
     procedure Dec (var p: any_pointer_type; Amount: Integer);

Description

For ordinal types, Dec decreases the value of x by one or by amount if specified.

If the argument p is pointing to a specified type (typed pointer), Dec decreases the address of p by the size of the type p is pointing to or by amount times that size respectively. If p is an untyped pointer (i.e. p is of type Pointer), p is decreased by one, otherwise by amount if specified.

Conforming to

Dec is a Borland Pascal extension. The combination of the second argument with application to pointers is a GNU Pascal extension.

Example

     program DecDemo;
     var
       x: Integer;
       y: array [1 .. 5] of Integer;
       p: ^Integer;
     begin
       x := 9;
       Dec (x, 10);  { yields -1 }
       {$X+}         { Turn on extended systax }
       p := @y[5];   { p points to y[5] }
       Dec (p, 3)    { p points to y[2] }
     end.

See also

Inc, Pred, Succ, Pointer Arithmetics.

Node: DefineSize, Next: , Previous: Dec, Up: Reference

DefineSize

(Under construction.)

Synopsis

     procedure DefineSize (var F: any_file; NewSize: Integer);

Description

Conforming to

DefineSize is a GNU Pascal extension.

Example

See also

Node: Delete, Next: , Previous: DefineSize, Up: Reference

Delete

(Under construction.)

Synopsis

     procedure Delete (var S: String; FirstChar, Count: Integer);
or 
     procedure Delete (var S: String; FirstChar: Integer);

Description

Conforming to

Delete is a UCSD Pascal extension. The possibility to omit the third parameter is a GNU Pascal extension.

Example

See also

Node: destructor, Next: , Previous: Delete, Up: Reference

destructor

(Under construction.)

Synopsis

Description

Object destructor.

Conforming to

destructor is an Object Pascal and a Borland Pascal extension.

Example

See also

Keywords.

Node: Dispose, Next: , Previous: destructor, Up: Reference

Dispose

(Under construction.)

Synopsis

     Dispose (PointerVar: Pointer);
or 
     Dispose (PointerVar: Pointer; tag_field_values);
or 
     Dispose (ObjectPointerVar: Pointer; destructor_call);

Description

Conforming to

Dispose is defined in ISO 7185 Pascal and supported by most known Pascal variants, but not by UCSD Pascal. Its use for objects is a Borland Pascal extension.

Example

See also

Node: div, Next: , Previous: Dispose, Up: Reference

div

Synopsis

     operator div (p, q: Integer) = r: Integer;

Description

Integer division operator.

Conforming to

div is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program DivDemo;
     
     var
       a, b: Integer;
     
     begin
       a := 16;
       b := 7;
       WriteLn (a div b);  { `2' }
     end.

See also

Keywords.

Node: do, Next: , Previous: div, Up: Reference

do

Synopsis

     for ... do
       statement
or 
     while ... do
       statement
or 
     with ... do
       statement
or 
     to begin do
       statement
or 
     to end do
       statement

Description

The do reserved word is used in combination with other Pascal keywords in many ways. For description and examples see the relevant reference sections: for, while, with, to begin, to end.

Conforming to

do is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See references.

See also

Keywords, for, while, with, to begin do, to end do.

Node: Double, Next: , Previous: do, Up: Reference

Double

(Under construction.)

Synopsis

     type
       Double = Real;

Description

Double is a synonym for the Real data type and supported for compatibility with other compilers.

Conforming to

Double is a Borland Pascal extension.

Example

     program DoubleDemo;
     var
       A: Double;  { There is nothing special with `Double'. }
       B: Real;
     begin
       A := Pi;
       A := B
     end.

See also

Node: downto, Next: , Previous: Double, Up: Reference

downto

Synopsis

     for variable := value1 downto value2 do
       statement

Description

The downto reserved word is used in combination with for to build a for loop.

Conforming to

downto is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See for.

See also

Keywords, for.

Node: else, Next: , Previous: downto, Up: Reference

else

Synopsis

As part of the if ... then ... else statement: 

     if Boolean_expression then
       statement1
     else
       statement2
or, as part of the case ... else statement: 
     case expression of
       selector: statement;
       ...
       selector: statement
     else  { ``otherwise'' instead of ``else'' is allowed }
       statement;
       ...
       statement
     end

Description

else is part of the if ... then ... else statement which provides a possibility to execute statements alternatively. In the case statement, else starts a series of statements which is executed if no selector fit in expression. In this situation, else is a synonym for otherwise.

Conforming to

else in if statements is defined in ISO 7185 Pascal and supported by all known Pascal variants. else in case statements is a Borland Pascal extension; ISO 10206 Extended Pascal has otherwise instead.

Example

     program ElseDemo;
     var
       i: Integer;
     begin
       Write ('Enter a number: ');
       ReadLn (i);
       if i > 42 then
         WriteLn ('The number is greater than 42')
       else
         WriteLn ('The number is not greater than 42')
     end.

See also

Keywords, if, case, otherwise.

Node: Empty, Next: , Previous: else, Up: Reference

Empty

(Under construction.)

Synopsis

     function Empty (var F: any_file): Boolean;

Description

Conforming to

Empty is an ISO 10206 Extended Pascal extension.

Example

See also

Node: end, Next: , Previous: Empty, Up: Reference

end

Synopsis

     begin
       statement;
       statement;
       ...
       statement
     end

Description

The reserved word end closes a begin ... end; statement which joins several statements together into one compound statement.

@@ end of a case statement @@ end of a record or object declaration @@ part of a to end do module destructor

Conforming to

end is defined in ISO 7185 Pascal and supported by all Pascal variants.

Example

     program EndDemo;
     begin
       if True then
         WriteLn ('single statement');
       if True then
         begin  { clamp statement1 ... }
           WriteLn ('statement1');
           WriteLn ('statement2')
         end    { ... to statement2 }
     end.

See also

Keywords, begin end Compound Statement, begin

Node: EOF, Next: , Previous: end, Up: Reference

EOF

(Under construction.)

Synopsis

     function EOF ([var F: any_file]): Boolean;
or 
     function EOF: Boolean;

Description

Conforming to

EOF is defined in ISO 7185 Pascal and supported by all Pascal variants.

Example

See also

Node: EOLn, Next: , Previous: EOF, Up: Reference

EOLn

(Under construction.)

Synopsis

     function EOLn ([var F: Text]): Boolean;
or 
     function EOLn: Boolean;

Description

Conforming to

EOLn is defined in ISO 7185 Pascal and supported by all Pascal variants.

Example

See also

Node: EpsReal, Next: , Previous: EOLn, Up: Reference

EpsReal

(Under construction.)

Synopsis

Description

Conforming to

EpsReal is an ISO 10206 Extended Pascal extension.

Example

See also

Node: EQ, Next: , Previous: EpsReal, Up: Reference

EQ

(Under construction.)

Synopsis

     function EQ (S1, S2: String): Boolean;

Description

Conforming to

EQ is an ISO 10206 Extended Pascal extension.

Example

See also

Node: EQPad, Next: , Previous: EQ, Up: Reference

EQPad

(Under construction.)

Synopsis

     function EQPad (S1, S2: String): Boolean;

Description

Conforming to

EQPad is a GNU Pascal extension.

Example

See also

Node: Erase, Next: , Previous: EQPad, Up: Reference

Erase

(Under construction.)

Synopsis

     procedure Erase (var F: any_file);

Description

Conforming to

Erase is a Borland Pascal extension.

Example

See also

Node: Exclude, Next: , Previous: Erase, Up: Reference

Exclude

Synopsis

     Exclude (set_variable, ordinal_value);

Description

Remove (subtract) a single element from a set. ordinal_value must be compatible with the base type of set_variable. Exclude is equivalent to: 

     set_variable := set_variable - [ordinal_value];

If set_variable does not contain ordinal_value, nothing happens.

Conforming to

Exclude is a Borland Pascal extension.

Example

     program ExcludeDemo;
     
     var
       Ch: Char;
       MyCharSet: set of Char;
     
     begin
       MyCharSet := ['P','N','L'];
       Exclude (MyCharSet , 'N'); { L, P }
     end.

See other examples in set and Set Operations.

See also

Keywords, Set Operations, set, in, Include.

Node: Exit, Next: , Previous: Exclude, Up: Reference

Exit

Synopsis

     procedure Exit;

Description

Exit leaves the currently executed procedure or function. Note: If Exit is called within the main program, it will be terminated instantly.

Conforming to

Exit is a UCSD Pascal extension. GNU Pascal supports it only as defined in Borland Pascal; not the following two UCSD Pascal uses: jumping out of several nested routines by giving an outer routine name as an optional argument, and Exit (program) which means the same as Halt.

Example

     program ExitDemo;
     
     procedure Foo (Bar: Integer);
     var
       Baz, Fac: Integer;
     begin
       if Bar < 1 then
         Exit;  { Exit `Foo' }
       Fac := 1;
       for Baz := 1 to Bar do
         begin
           Fac := Fac * Baz;
           if Fac >= Bar then
             Exit;  { Exit `Foo' }
           WriteLn (Bar,' is greater than ', Baz, '!, which is equal to ', Fac)
       end
     end;
     
     begin
       Foo (-1);
       Foo (789);
       Exit;            { Terminates program }
       Foo (987654321)  { This is not executed anymore }
     end.

See also

Break, Continue, Halt.

Node: Exp, Next: , Previous: Exit, Up: Reference

Exp

Synopsis

     function Exp (x: Real): Real;
or 
     function Exp (z: Complex): Complex;

Description

The exponential function Exp computes the value of e to the power of x, where the Euler number e = Exp (1) is the base of the natural logarithm.

Conforming to

The function Exp is defined in ISO 7185 Pascal; its application to complex values is defined in ISO 10206 Extended Pascal.

Example

     program ExpDemo;
     var
       z: Complex;
     begin
       z := Cmplx (1, - 2 * Pi);  { z = 1 - 2 pi i }
       z := Exp (z);  { yields e = Exp (1), since Exp ix = Cos x + i Sin x }
       WriteLn (Ln (Re (z)) : 0 : 5)  { prints 1 = Ln (Exp (1)) }
     end.

See also

Ln

Node: export, Next: , Previous: Exp, Up: Reference

export

(Under construction.)

Synopsis

     export interface_name = (identifier, identifier, ...);

or 

     export interface_name = all;

Description

Interface export for Extended Pascal modules.

all means to automatically export all identifiers declared in the interface module.

Conforming to

export is an ISO 10206 Extended Pascal extension. It also exists in Borland Pascal, but with a different meaning, not (yet) supported by GPC.

export all is a GNU Pascal extension.

Example

     program ExportDemo;
     
     import AllInterface in 'somemodule.pas';
     
     begin
       Bar (a);
       WriteLn (b)
     end.
     
     module SomeModule interface;
     
     export
       SomeInterface = (a);
       AllInterface = all;  { Same as `AllInterface = (a, b, Bar);' }
     
     var
       a, b: Integer;
     
     procedure Bar (i: Integer);
     
     end.
     
     module SomeModule implementation;
     
     procedure Bar (i: Integer);
     begin
       b := a
     end;
     
     to begin do
       a := 42;
     
     end.

See also

Keywords, Modules.

Node: exports, Next: , Previous: export, Up: Reference

exports

Not yet implemented.

Synopsis

Description

Library export.

Conforming to

exports is a Borland Pascal extension.

Example

See also

Keywords.

Node: Extend, Next: , Previous: exports, Up: Reference

Extend

(Under construction.)

Synopsis

     procedure Extend (var F: any_file; [FileName: String;]
                                         [BlockSize: Cardinal]);

Description

Extend opens a file for writing. If the file does not exist, it is created. If it does exist, the file pointer is positioned after the last element.

Like Rewrite, Reset and Append do, Extend accepts an optional second and third parameter for the name of the file in the filesystem and, for untyped files, the block size of the file. (For details, see Rewrite.)

Conforming to

Extend is an ISO 10206 Extended extension. Borland Pascal has Append instead. The BlockSize parameter is a Borland Pascal extension. The FileName parameter is a GNU Pascal extension.

Example

     program ExtendDemo;
     var
       Sample: Text;
     begin
       Assign (Sample, 'sample.txt');
       Rewrite (Sample);
       WriteLn (Sample, 'Hello, World!');  { `sample.txt' now has one line }
       Close (Sample);
     
       { ... }
     
       Extend (Sample);
       WriteLn (Sample, 'Hello again!');  { `sample.txt' now has two lines }
       Close (Sample)
     end.

See also

Assign, Reset, Rewrite, Update, Append.

Node: Extended, Next: , Previous: Extend, Up: Reference

Extended

(Under construction.)

Synopsis

     type
       Extended = LongReal;

Description

Conforming to

Extended is a Borland Pascal extension.

Example

     program ExtendedDemo;
     var
       a: Extended;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Node: external, Next: , Previous: Extended, Up: Reference

external

(Under construction.)

Synopsis

     declaration external;

or 

     declaration external name linker_name;

Description

Declaration of external object.

Conforming to

external is a UCSD Pascal extension.

Example

See also

Keywords.

Node: Fail, Next: , Previous: external, Up: Reference

Fail

(Under construction.)

Synopsis

Description

Conforming to

Fail is a Borland Pascal extension.

Example

See also

Node: False, Next: , Previous: Fail, Up: Reference

False

Synopsis

     type
       Boolean = (False, True);  { built-in type }

Description

False is one of the two Boolean values and is used to represent a condition which is never fullfilled. For example, the expression, 1 = 2 always yields False. It is the opposite of True. False has the ordinal value 0.

Conforming to

False is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program FalseDemo;
     
     var
       a: Boolean;
     
     begin
       a := 1 = 2;  { yields False }
       WriteLn (Ord (False));  { 0 }
       WriteLn (a);  { False }
       if False then WriteLn ('This is not executed.')
     end.

See also

Boolean (Intrinsic), True, Boolean.

Node: far, Next: , Previous: False, Up: Reference

far

Synopsis

Description

The far directive can be appended to a procedure or function heading but is ignored by GPC. It is there for Borland compatibility, only. (Since the GNU compilers provide a flat memory model, the distinction between near and far pointers is void.)

Conforming to

far is a Borland Pascal extension.

Example

     program FarDemo;
     
     var
       p: procedure;
     
     {$W no-near-far}  { Don't warn about the uselessness of `far' }
     
     procedure Foo; far;  { `far' has no effect in GPC }
     begin
       WriteLn ('Foo')
     end;
     
     begin
       p := Foo;  { Would also work without `far' in GPC. }
       p
     end.

See also

Keywords, near.

Node: file, Next: , Previous: far, Up: Reference

file

(Under construction.)

Synopsis

In type definitions: 

     File of Type
or 
     File

Description

Non-text file type declaration.

Conforming to

file is a Borland Pascal extension.

Example

See also

Keywords, Text, AnyFile.

Node: FilePos, Next: , Previous: file, Up: Reference

FilePos

(Under construction.)

Synopsis

     function FilePos (var F: any_file): Integer;

Description

Conforming to

FilePos is a Borland Pascal extension.

Example

See also

Node: FileSize, Next: , Previous: FilePos, Up: Reference

FileSize

(Under construction.)

Synopsis

     function FileSize (var F: any_file): Integer;

Description

Conforming to

FileSize is a Borland Pascal extension.

Example

See also

Node: FillChar, Next: , Previous: FileSize, Up: Reference

FillChar

(Under construction.)

Synopsis

     procedure FillChar (var Dest; Count: SizeType; Val: Char);
or 
     procedure FillChar (var Dest; Count: SizeType; Val: Byte);

Description

Conforming to

FillChar is a UCSD Pascal extension.

Example

See also

Node: finalization, Next: , Previous: FillChar, Up: Reference

finalization

(Under construction.)

Synopsis

Description

Unit finalization.

It is equivalent to Extended Pascal's to end do.

Conforming to

finalization is a Borland Delphi extension.

Example

See also

Keywords, initialization, to end do.

Node: Finalize, Next: , Previous: finalization, Up: Reference

Finalize

(Under construction.)

Synopsis

     procedure Finalize (var Aynthing);

Description

Finalize does all necessary clean-ups for the parameter. This is normally done automatically when a variable goes out of scope, so you need to call Finalize only in special situations, e.g. when you deallocate a dynamic variable with FreeMem rather than Dispose.

Conforming to

Finalize is a Borland Delphi extension.

Example

See also

Initialize, Dispose, FreeMem.

Node: Flush, Next: , Previous: Finalize, Up: Reference

Flush

(Under construction.)

Synopsis

     procedure Flush (var F: any_file);

Description

Conforming to

Flush is a Borland Pascal extension.

Example

See also

Node: for, Next: , Previous: Flush, Up: Reference

for

Synopsis

For ordinal index variables: 

     for ordinal_variable := initial_value to final_value do
       statement
or 
     for ordinal_variable := initial_value downto final_value do
       statement

For sets: 

     for set_element_type_variable in some_set do
       statement

For pointer index variables: 

     for pointer_variable := initial_address to final_address do
       statement
or 
     for pointer_variable := initial_address downto final_address do
       statement

@@ Set member iteration

Description

The for statement is a count loop. For further information see for Statement.

Conforming to

for is defined in ISO 7185 Pascal and supported by all Pascal variants. Iteration of Pointers is a Borland Pascal extension. Set member iteration is an ISO 10206 Extended Pascal extension.

Example

     program ForDemo;
     var
       CharSet: set of Char;
       c: Char;
       n: Integer;
       Fac: array [0 .. 10] of Integer;
       PInt: ^Integer;
     begin
        CharSet := ['g', 'p', 'c'];
        for c in CharSet do
          WriteLn (c);  { prints `c', `g', `p' in three lines }
        Fac[0] := 1;
        for n := 1 to 10 do  { computes the factorial of n for n = 0 .. 10 }
          Fac[n] := Fac[n - 1] * n;
        {$X+}
        { prints n! for n = 0 .. 10 }
        for PInt := @Fac[0] to @Fac[10] do
          WriteLn (PInt - @Fac[0], '! = ', PInt^)
     end.

See also

Keywords, Set Types, Pointer Arithmetics

Node: FormatString, Next: , Previous: for, Up: Reference

FormatString

(Under construction.)

Synopsis

Description

Conforming to

FormatString is a GNU Pascal extension.

Example

See also

Node: forward, Next: , Previous: FormatString, Up: Reference

forward

(Under construction.)

Synopsis

Description

Declaration of a routine whose definition follows below.

Conforming to

forward is a UCSD Pascal extension.

Example

See also

Keywords.

Node: Frac, Next: , Previous: forward, Up: Reference

Frac

Synopsis

     function Frac (x: Real): Real;

Description

Frac returns the fractional part of a floating point number.

Conforming to

Frac is a Borland Pascal extension.

Example

     program FracDemo;
     
     begin
       WriteLn (Frac (12.345) : 1 : 5);  { 0.34500 }
       WriteLn (Int (12.345) : 1 : 5);  { 12.00000 }
       WriteLn (Round (12.345) : 1);  { 12 }
       WriteLn (Trunc (12.345) : 1);  { 12 }
     
       WriteLn (Frac (-12.345) : 1 : 5);  { -0.34500 }
       WriteLn (Int (-12.345) : 1 : 5);  { -12.00000 }
       WriteLn (Round (-12.345) : 1);  { -12 }
       WriteLn (Trunc (-12.345) : 1);  { -12 }
     
       WriteLn (Frac (12.543) : 1 : 5);  { 0.54300 }
       WriteLn (Int (12.543) : 1 : 5);  { 12.00000 }
       WriteLn (Round (12.543) : 1);  { 13 }
       WriteLn (Trunc (12.543) : 1);  { 12 }
     
       WriteLn (Frac (-12.543) : 1 : 5);  { -0.54300 }
       WriteLn (Int (-12.543) : 1 : 5);  { -12.00000 }
       WriteLn (Round (-12.543) : 1);  { -13 }
       WriteLn (Trunc (-12.543) : 1);  { -12 }
     end.

See also

Real Types, Real, Int, Round, Trunc.

Node: FrameAddress, Next: , Previous: Frac, Up: Reference

FrameAddress

(Under construction.)

Synopsis

Description

Conforming to

FrameAddress is a GNU Pascal extension.

Example

See also

Node: FreeMem, Next: , Previous: FrameAddress, Up: Reference

FreeMem

Synopsis

     procedure FreeMem (var p: Pointer; Size: Cardinal);
or 
     procedure FreeMem (var p: Pointer);

Description

Releases a chunk of memory previously allocated using GetMem. The parameter Size is optional. Its value is currently ignored.

Since Extended Pascal's schemata provide a cleaner way to implement dynamical arrays and such, we recommend using GetMem and FreeMem only for low-level applications or for interfacing with other languages.

Conforming to

FreeMem is a Borland Pascal extension. FreeMem with only one parameter is a GNU Pascal extension.

Example

See GetMem.

See also

GetMem, Schema Types, Dispose, Mark, Release.

Node: function, Next: , Previous: FreeMem, Up: Reference

function

(Under construction.)

Synopsis

Description

Function declaration.

Conforming to

function is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Keywords.

Node: GE, Next: , Previous: function, Up: Reference

GE

(Under construction.)

Synopsis

     function GE (S1, S2: String): Boolean;

Description

Conforming to

GE is an ISO 10206 Extended Pascal extension.

Example

See also

Node: GEPad, Next: , Previous: GE, Up: Reference

GEPad

(Under construction.)

Synopsis

     function GEPad (S1, S2: String): Boolean;

Description

Conforming to

GEPad is a GNU Pascal extension.

Example

See also

Node: Get, Next: , Previous: GEPad, Up: Reference

Get

(Under construction.)

Synopsis

     procedure Get (var F: typed_file);

Description

Conforming to

Get is defined in ISO 7185 Pascal and supported by all known Pascal variants except UCSD/Borland Pascal and its variants.

Example

See also

Node: GetMem, Next: , Previous: Get, Up: Reference

GetMem

Synopsis

     procedure GetMem (var p: Pointeger; Size: Cardinal);

Description

Allocates dynamical storage on the heap and returns a pointer to it in p.

Since Extended Pascal's schemata provide a cleaner way to implement dynamical arrays and such, we recommend using GetMem and FreeMem only for low-level applications.

Conforming to

GetMem is a Borland Pascal extension.

Example

The Borland-comatibility unit Graph from the BPcompat package supports a GetImage and a PutImage procedure which need a variable of size ImageSize as a buffer. Since these are "black box" routines, the buffer can't reasonably be a schema providing a dynamical array. Instead, we have to use GetMem and FreeMem for dynamical memory allocation. 

     program GetMemDemo;
     var
       Buffer: Pointer;
       Size: Cardinal;
     begin
       Size := Random (10000);  { the size can be determined at run time }
       GetMem (Buffer, Size);
       { Do something with Buffer }
       FreeMem (Buffer)  { or: FreeMem (Buffer, Size) }
     end.

See also

FreeMem, New, Schema Types.

Node: GetTimeStamp, Next: , Previous: GetMem, Up: Reference

GetTimeStamp

Synopsis

     procedure GetTimeStamp (var T: TimeStamp);

Description

GetTimeStamp gets the current local date and time as a TimeStamp record containing the Year, Month, Day, Hour, Minute, Second, and so on.

Conforming to

GetTimeStamp is an ISO 10206 Extended Pascal extension.

Example

Set TimeStamp.

See also

TimeStamp, Date, Time, Date And Time Routines.

Node: goto, Next: , Previous: GetTimeStamp, Up: Reference

goto

(Under construction.)

Synopsis

     goto label

Description

The goto statement transfers control to statement with the label label.

Conforming to

goto is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Keywords.

Node: GT, Next: , Previous: goto, Up: Reference

GT

(Under construction.)

Synopsis

     function GT (S1, S2: String): Boolean;

Description

Conforming to

GT is an ISO 10206 Extended Pascal extension.

Example

See also

Node: GTPad, Next: , Previous: GT, Up: Reference

GTPad

(Under construction.)

Synopsis

     function GTPad (S1, S2: String): Boolean;

Description

Conforming to

GTPad is a GNU Pascal extension.

Example

See also

Node: Halt, Next: , Previous: GTPad, Up: Reference

Halt

Synopsis

     Halt;
or 
     Halt (ExitCode: Integer);

Description

Halt terminates the program with exitcode 0. If ExitCode, is specified, it is returned by Halt on exit.

Conforming to

Halt is an Extended Pascal and a UCSD Pascal extension.

Example

     program HaltDemo;
     begin
       WriteLn ('This string will always be this program''s output.');
       Halt;  { Terminate right here and right now. }
       WriteLn ('And this string won''t ever!')
     end.

See also

Break, Continue, Exit, Return, goto.

Node: High, Next: , Previous: Halt, Up: Reference

High

Synopsis

     function High (ordinal_type_or_variable): ordinal_type;
or 
     function High (array_type_or_variable): array_index_type;
or 
     function High (string_variable): Integer;

Description

For ordinal types or variables of that type, High returns the highest value a variable of that type can assume.

For array types or variables of that type, High returns the highest index a variable of that type can assume. Note: the result is of the same type as the array index is. If the array has more than one dimension, High returns the highest index in the first dimension.

If the argument is a string variable, High returns the discriminant of the string type (i.e. its capacity).

Conforming to

High is a Borland Pascal extension.

Example

     program HighDemo;
     type
       Colors = (Red, Green, Blue);
     var
       Col: array [Colors] of (Love, Hope, Faithfulness);
       Foo: Colors;
       Bar: Integer;
       Baz: String (123);
     begin
       Foo := High (Col);             { yields Blue }
       Bar := Ord (High (Col[Foo]));  { yields Ord (Faithfulness), i.e., 2 }
       Bar := High (Integer);         { returns highest possible ``Integer'' }
       Bar := High (Baz)              { returns 123 }
     end.

See also

Low

Node: if, Next: , Previous: High, Up: Reference

if

Synopsis

     if Boolean_expression then
       statement
or with an alternative statement: 
     if Boolean_expression then
       statement1
     else
       statement2

Description

The if ... then statement executes statement1 depending on Boolean expression being true. If else is specified, it continues executing statement2 instead.

Conforming to

if is defined in ISO 7185 Pascal and supported by all Pascal variants.

Example

     program IfDemo;
     var
       Foo, Bar: Boolean;
     begin
       Foo := True;
       Bar := False;
       if ((1 = 1) or (2 = 3)) and (Foo = not Bar) then
         begin
           { This is executed if either Foo is true but not Bar or vice versa }
           WriteLn ('Either Foo or Bar is true.');
           if Bar then
             WriteLn ('You will see this text if Bar is true.')
         end
       else { This whole `else' branch is not executed }
         if 1 = 1 then
           if True = False then
             WriteLn ('This text is never written on screen.')
           else  { Note: This ``else'' belongs to ``if True = False'' }
             WriteLn ('This text is never written on screen as well.')
         else  { Note: This ``else'' belongs to ``if 1 = 1'' }
           WriteLn ('Nor is this.')
     end.

See also

Keywords, if Statement, else, then

Node: Im, Next: , Previous: if, Up: Reference

Im

Synopsis

     function Im (z: Complex): Real;

Description

Im extracts the imaginary part of the complex number z. The result is a real value.

Conforming to

Im is an ISO 10206 Extended Pascal extension.

Example

     program ImDemo;
     var
       z: Complex;
     begin
       z := Cmplx (1, 2);  { 1 + i * 2 }
       WriteLn (Im (z) : 0 : 5)  { 2.00000 }
     end.

See also

Cmplx, Re, Arg.

Node: implementation, Next: , Previous: Im, Up: Reference

implementation

(Under construction.)

Synopsis

Description

Module or unit implementation part.

Conforming to

implementation is an Extended Pascal and a UCSD Pascal extension.

Example

See also

Keywords.

Node: import, Next: , Previous: implementation, Up: Reference

import

Synopsis

     program @@fragment foo;
     
     import
       bar1;
       bar3 (baz1 => glork1) in 'baz.pas';
       bar2 only (baz2, baz3 => glork2);
     
     [...]

Description

The reserved word import in the import part of a program makes the program import an interface.

The in above tells GPC to look for the module in the specified file; otherwise the file name is derived from the name of the interface by adding first .p, then .pas - which only works if the name of the exported interface coincides with the file name.

The symbol => denotes import renaming: The entity which is exported under the name baz1 by the interface bar3 will be known under the new name glork1 in the program.

The only qualifier means that only the listed identifiers will be imported from the interface. Renaming works together with only, too.

There must be at most one import part in a program.

The interfaces needn't be exported by Extended Pascal modules but may be UCSD/Borland Pascal units as well.

Conforming to

import and modules in general are an ISO 10206 Extended Pascal extension.

GNU Pascal does not yet support qualified import.

Example

See also

Keywords, module, unit, uses.

Node: in, Next: , Previous: import, Up: Reference

in

Synopsis

As part of the set membership test, as a boolean expression: 

     ordinal_value in set_expression
or, as part of a for loop iterating through a set: 
     for ordinal_variable in set_expression do ...

Description

When in is used as a membership test, it acts as a binary operator taking ordinal_value as its left parameter and set_expression as its right parameter and returning a boolean result which is true if set_expression contains the element ordinal_value.

When in is used as part of a for loop, it iterates ordinal_variable over the elements contained in set_expression, that is every ordinal_value that would return true if tested as ordinal_value in set_expression.

Conforming to

in is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

Set set

See also

Keywords, Set Operations, set, Exclude, Include, for.

Node: Inc, Next: , Previous: in, Up: Reference

Inc

Synopsis

For ordinal types: 

     procedure Inc (var x: ordinal_type);
or 
     procedure Inc (var x: ordinal_type; Amount: Integer);

For pointer types: 

     procedure Inc (var p: any_pointer_type);
or 
     procedure Inc (var p: any_pointer_type; Amount: Integer);

Description

For ordinal types, inc increases the value of x by one or by amount if it is given.

If the argument p is pointing to a specified type (typed pointer), inc increases the address of p by the size of the type p is pointing to or by amount times that size respectively. If p is an untyped pointer (i.e. p is of type Pointer), p is increased by one.

Conforming to

Inc is a Borland Pascal extension. Yet application of Inc to pointers is defined in Borland Pascal. The combination of the second argument with application to pointers is a GNU Pascal extension.

Example

     program IncDemo;
     var
       Foo: Integer;
       Bar: array [1 .. 5] of Integer;
       Baz: ^Integer;
     begin
       Foo := 4;
       Inc (Foo, 5);    { yields 9 }
       {$X+}            { Turn on extended systax }
       Baz := @Bar[1];  { Baz points to y[1] }
       Inc (Baz, 2);    { Baz points to y[3] }
     end.

See also

Dec, Pred, Succ, Pointer Arithmetics.

Node: Include, Next: , Previous: Inc, Up: Reference

Include

Synopsis

     Include (set_variable, ordinal_value);

Description

Add (join) a single element to a set. ordinal_value must be compatible with the base type of set_variable. Include is equivalent to: 

     set_variable := set_variable + [ordinal_value];

If set_variable already contains ordinal_value, nothing happens.

Conforming to

Include is a Borland Pascal extension.

Example

     program IncludeDemo;
     
     var
       Ch: Char;
       MyCharSet: set of Char;
     
     begin
       MyCharSet := ['P','N','L'];
       Include (MyCharSet , 'A');  { A, L, N, P }
     end.

See other examples in set and Set Operations.

See also

Keywords, Set Operations, set, in, Exclude.

Node: Index, Next: , Previous: Include, Up: Reference

Index

(Under construction.)

Synopsis

Description

Conforming to

Index is an ISO 10206 Extended Pascal extension.

Example

See also

Node: inherited, Next: , Previous: Index, Up: Reference

inherited

(Under construction.)

Synopsis

Description

Reference to methods of ancestor object types.

Conforming to

inherited is an Object Pascal, Borland Pascal and traditional Macintosh Pascal extension.

Example

See also

Keywords.

Node: initialization, Next: , Previous: inherited, Up: Reference

initialization

(Under construction.)

Synopsis

Description

Unit initialization.

It is equivalent to Extended Pascal's to begin do.

Conforming to

initialization is a Borland Delphi extension.

Example

See also

Keywords, finalization, to begin do.

Node: Initialize, Next: , Previous: initialization, Up: Reference

Initialize

(Under construction.)

Synopsis

     procedure Initialize (var Aynthing);

Description

Initialize does all necessary initializations for the parameter (e.g., setting of string and schema discriminants, and object VMT pointers, initialization of file variables). This is normally done automatically at the start of the lifetime of a variable, so you need to call Initialize only in special situations, e.g. when you allocate a dynamic variable with GetMem rather than New.

Conforming to

Initialize is a Borland Delphi extension.

Example

See also

Finalize, New, GetMem.

Node: InOutRes, Next: , Previous: Initialize, Up: Reference

InOutRes

(Under construction.)

Synopsis

     var
       InOutRes: Integer;

Description

Conforming to

InOutRes is a UCSD Pascal extension.

Example

See also

Node: Input, Next: , Previous: InOutRes, Up: Reference

Input

(Under construction.)

Synopsis

     var
       Input: Text;

Description

Conforming to

Input is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Node: Insert, Next: , Previous: Input, Up: Reference

Insert

(Under construction.)

Synopsis

     procedure Insert (Source: String; var Dest: String; Position: Integer);

Description

Conforming to

Insert is a UCSD Pascal extension.

Example

See also

Node: Int, Next: , Previous: Insert, Up: Reference

Int

Synopsis

     function Int (x: Real): Real;

Description

Int returns the integer part of a floating point number as a floating point number. Use Trunc to get the integer part as an integer.

Conforming to

Int is a UCSD Pascal extension.

Example

     program IntDemo;
     
     begin
       WriteLn (Frac (12.345) : 1 : 5);  { 0.34500 }
       WriteLn (Int (12.345) : 1 : 5);  { 12.00000 }
       WriteLn (Round (12.345) : 1);  { 12 }
       WriteLn (Trunc (12.345) : 1);  { 12 }
     
       WriteLn (Frac (-12.345) : 1 : 5);  { -0.34500 }
       WriteLn (Int (-12.345) : 1 : 5);  { -12.00000 }
       WriteLn (Round (-12.345) : 1);  { -12 }
       WriteLn (Trunc (-12.345) : 1);  { -12 }
     
       WriteLn (Frac (12.543) : 1 : 5);  { 0.54300 }
       WriteLn (Int (12.543) : 1 : 5);  { 12.00000 }
       WriteLn (Round (12.543) : 1);  { 13 }
       WriteLn (Trunc (12.543) : 1);  { 12 }
     
       WriteLn (Frac (-12.543) : 1 : 5);  { -0.54300 }
       WriteLn (Int (-12.543) : 1 : 5);  { -12.00000 }
       WriteLn (Round (-12.543) : 1);  { -13 }
       WriteLn (Trunc (-12.543) : 1);  { -12 }
     end.

See also

Real Types, Real, Frac, Round, Trunc.

Node: Integer, Next: , Previous: Int, Up: Reference

Integer

Synopsis

     type
       Integer  { built-in type }

Description

Integer is the "natural" signed integer type in GNU Pascal. On most platforms it is 32 bits wide and thus has a range of -2147483648 .. 2147483647. Use it whenever you need a general-purpose signed integer type.

Integer in GNU Pascal is compatible to Int in GNU C.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

In ISO Pascal, Integer is the only built-in integer type. (However see Subrange Types.)

Example

     program IntegerDemo;
     var
       a: Integer;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: interface, Next: , Previous: Integer, Up: Reference

interface

(Under construction.)

Synopsis

Description

Module or unit interface part.

Conforming to

interface is an Extended Pascal and a UCSD Pascal extension.

Example

See also

Keywords.

Node: interrupt, Next: , Previous: interface, Up: Reference

interrupt

Not yet implemented.

Synopsis

Description

Interrupt handler declaration (not yet implemented).

Conforming to

interrupt is a Borland Pascal extension.

Example

See also

Keywords.

Node: IOResult, Next: , Previous: interrupt, Up: Reference

IOResult

(Under construction.)

Synopsis

     function IOResult: Integer;

Description

Conforming to

IOResult is a UCSD Pascal extension.

Example

See also

Node: is, Next: , Previous: IOResult, Up: Reference

is

Synopsis

Description

Object type membership test.

Conforming to

is is an Object Pascal and a Borland Delphi extension.

Example

See also

Keywords, as, TypeOf, OOP.

Node: label, Next: , Previous: is, Up: Reference

label

(Under construction.)

Synopsis

Description

Label declaration for a goto statement.

Conforming to

label is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Keywords.

Node: LastPosition, Next: , Previous: label, Up: Reference

LastPosition

(Under construction.)

Synopsis

     function LastPosition (var F: typed_file): Integer;

Description

Conforming to

LastPosition is an ISO 10206 Extended Pascal extension.

Example

See also

Node: LE, Next: , Previous: LastPosition, Up: Reference

LE

(Under construction.)

Synopsis

     function LE (S1, S2: String): Boolean;

Description

Conforming to

LE is an ISO 10206 Extended Pascal extension.

Example

See also

Node: Length, Next: , Previous: LE, Up: Reference

Length

(Under construction.)

Synopsis

     function Length (S: String): Integer;

Description

Conforming to

Length is an Extended Pascal and a UCSD Pascal extension.

Example

See also

Node: LEPad, Next: , Previous: Length, Up: Reference

LEPad

(Under construction.)

Synopsis

     function LEPad (S1, S2: String): Boolean;

Description

Conforming to

LEPad is a GNU Pascal extension.

Example

See also

Node: library, Next: , Previous: LEPad, Up: Reference

library

Not yet implemented.

Synopsis

Description

Library declaration.

Conforming to

library is a Borland Pascal extension.

Example

See also

Keywords.

Node: Ln, Next: , Previous: library, Up: Reference

Ln

Synopsis

     function Ln (x: Real): Real;
or 
     function Ln (z: Complex): Complex;

Description

The natural logarith Ln is the logarithm with base e, where e is the Euler number e = Exp (1) = 2.718281828...

Conforming to

The function Ln is defined in ISO 7185 Pascal; its application to complex values is defined in ISO 10206 Extended Pascal.

Example

     program LnDemo;
     var
       z: Complex;
     begin
       z := Cmplx (1, 1);
       z := Ln (z)  { yields Ln (SqRt (2)) + i * Pi / 4 }
                    { since Ln (i * x) = Ln Abs (x) + i * Arg (x) }
     end.

See also

Node: LoCase, Next: , Previous: Ln, Up: Reference

LoCase

(Under construction.)

Synopsis

     function LoCase (Ch: Char): Char;

Description

Conforming to

LoCase is a GNU Pascal extension.

Example

See also

Node: LongBool, Next: , Previous: LoCase, Up: Reference

LongBool

Synopsis

     type
       LongBool = Boolean attribute (Size = BitSizeOf (LongInt));

Description

The intrinsic LongBool represents boolean values, but occupies the same memory space as a LongInt. It is used when you need to define a parameter or record that conforms to some external library or system specification.

Conforming to

LongBool is a Borland Pascal extension.

Example

     program LongBoolDemo;
     var
       a: LongBool;
     begin
       LongInt (a) := 1;
       if a then WriteLn ('Ord (True) = 1')
     end.

See also

Boolean (Intrinsic), Boolean, True, False, CBoolean, ByteBool, ShortBool, MedBool, WordBool, LongestBool.

Node: LongCard, Next: , Previous: LongBool, Up: Reference

LongCard

Synopsis

     type
       LongCard = Cardinal attribute (Size = BitSizeOf (LongInt));

Description

LongCard is an unsigned integer type which is longer than Cardinal. On most platforms it is 64 bits wide and thus has a range of 0..18446744073709551615.

LongCard in GNU Pascal is compatible to long long unsigned int in GNU C.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

LongCard is a GNU Pascal extension.

Example

     program LongCardDemo;
     var
       a: LongCard;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: LongestBool, Next: , Previous: LongCard, Up: Reference

LongestBool

Synopsis

     type
       LongestBool = Boolean attribute (Size = BitSizeOf (LongestInt));

Description

The intrinsic LongestBool represents boolean values, but occupies the same memory space as a LongestInt. It is used when you need to define a parameter or record that conforms to some external library or system specification.

Conforming to

LongestBool is a GNU Pascal extension.

Example

     program LongestBoolDemo;
     var
       a: LongestBool;
     begin
       LongestInt (a) := 1;
       if a then WriteLn ('Ord (True) = 1')
     end.

See also

Boolean (Intrinsic), Boolean, True, False, CBoolean, ByteBool, ShortBool, MedBool, WordBool, LongBool.

Node: LongestCard, Next: , Previous: LongestBool, Up: Reference

LongestCard

Synopsis

     type
       LongestCard = Cardinal attribute (Size = BitSizeOf (LongestInt));

Description

LongestCard is GPC's longest-possible unsigned integer type. Currently, this is the same as LongCard. On most platforms it is 64 bits wide and thus has a range of 0..18446744073709551615.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

LongestCard is a GNU Pascal extension.

Example

     program LongestCardDemo;
     var
       a: LongestCard;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: LongestInt, Next: , Previous: LongestCard, Up: Reference

LongestInt

Synopsis

     type
       LongestInt = LongInt;  { might get bigger than LongInt someday }

Description

LongestInt is GPC's longest-possible signed integer type. Currently, this is the same as LongInt. On most platforms it is 64 bits wide and thus has a range of -9223372036854775808..9223372036854775807.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

LongestInt is a GNU Pascal extension.

Example

     program LongestIntDemo;
     var
       a: LongestInt;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: LongestReal, Next: , Previous: LongestInt, Up: Reference

LongestReal

(Under construction.)

Synopsis

     type
       LongestReal = LongReal;  { might get bigger than LongReal someday }

Description

Conforming to

LongestReal is a GNU Pascal extension.

Example

     program LongestRealDemo;
     var
       a: LongestReal;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Node: LongestWord, Next: , Previous: LongestReal, Up: Reference

LongestWord

Synopsis

     type
       LongestWord = LongestCard;

Description

LongestWord is GPC's longest-possible unsigned integer type. Currently, this is the same as LongWord. On most platforms it is 64 bits wide and thus has a range of 0..18446744073709551615. (It is the same as LongestCard.)

There are lots of other integer types in GPC, see Integer Types.

Conforming to

LongestWord is a GNU Pascal extension.

Example

     program LongestWordDemo;
     var
       a: LongestWord;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: LongInt, Next: , Previous: LongestWord, Up: Reference

LongInt

Synopsis

     type
       LongInt  { built-in type }

Description

LongInt is a signed integer type which is longer than Integer. On most platforms it is 64 bits wide and thus has a range of -9223372036854775808..9223372036854775807.

LongInt in GNU Pascal is compatible to long long int in GNU C.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

LongInt is a Borland Pascal extension. Borland Pascal defines LongInt as a 32-bit signed integer type (Integer in GNU Pascal).

Example

     program LongIntDemo;
     var
       a: LongInt;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: LongReal, Next: , Previous: LongInt, Up: Reference

LongReal

(Under construction.)

Synopsis

     type
       LongReal  { built-in type }

Description

Conforming to

LongReal is a GNU Pascal extension.

Example

     program LongRealDemo;
     var
       a: LongReal;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Node: LongWord, Next: , Previous: LongReal, Up: Reference

LongWord

Synopsis

     type
       LongWord = LongCard;

Description

LongWord is an unsigned integer type which is larger than Word. On most platforms it is 64 bits wide and thus has a range of 0..18446744073709551615. It is the same as LongCard.

LongWord in GNU Pascal is compatible to long long unsigned int in GNU C.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

LongWord is a GNU Pascal extension.

Example

     program LongWordDemo;
     var
       a: LongWord;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: Low, Next: , Previous: LongWord, Up: Reference

Low

Synopsis

     function Low (ordinal_type_or_variable): ordinal_type;
or 
     function Low (array_type_or_variable): array_element_type;
or 
     function Low (string_variable): Integer;

Description

For ordinal types or variables of that type, Low returns the lowest value a variable of that type can assume.

For array types or variables of that type, Low returns the lowest index a variable of that type can assume. Note: the result is of the same type as the array index is. If the array has more than one dimension, Low returns the lowest index in the first dimension.

If the argument is a string variable, Low returns one.

Conforming to

Low is a Borland Pascal extension.

Example

     program LowDemo;
     type
       Colors = (Red, Green, Blue);
     var
       Col: array [12 .. 20] of Colors;
       Foo: 12 .. 20;
       Bar: Integer;
     begin
       Foo := Low (Col);            { returns 12 }
       Col[Foo] := Low (Col[Foo]);  { returns Red }
       Bar := Low (Integer)         { returns lowest ``Integer'' value }
     end.

See also

High

Node: LT, Next: , Previous: Low, Up: Reference

LT

(Under construction.)

Synopsis

     function LT (S1, S2: String): Boolean;

Description

Conforming to

LT is an ISO 10206 Extended Pascal extension.

Example

See also

Node: LTPad, Next: , Previous: LT, Up: Reference

LTPad

(Under construction.)

Synopsis

     function LTPad (S1, S2: String): Boolean;

Description

Conforming to

LTPad is a GNU Pascal extension.

Example

See also

Node: Mark, Next: , Previous: LTPad, Up: Reference

Mark

(Under construction.)

Synopsis

     procedure Mark (var P: Pointer);

Description

Conforming to

Mark is a UCSD Pascal extension.

Example

See also

Node: Max, Next: , Previous: Mark, Up: Reference

Max

(Under construction.)

Synopsis

     function Max (x1, x2: ordinal_or_real_type): same_type;

Description

Conforming to

Max is a GNU Pascal extension.

Example

See also

Node: MaxChar, Next: , Previous: Max, Up: Reference

MaxChar

(Under construction.)

Synopsis

Description

The value of MaxChar is the largest value of Char.

Conforming to

MaxChar is an ISO 10206 Extended Pascal extension.

Example

See also

Node: MaxInt, Next: , Previous: MaxChar, Up: Reference

MaxInt

(Under construction.)

Synopsis

Description

The MaxInt constant defines the maximum value of Integer. This constant is a built-in compiler value.

Conforming to

MaxInt is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Node: MaxReal, Next: , Previous: MaxInt, Up: Reference

MaxReal

(Under construction.)

Synopsis

Description

Conforming to

MaxReal is an ISO 10206 Extended Pascal extension.

Example

See also

MinReal.

Node: MedBool, Next: , Previous: MaxReal, Up: Reference

MedBool

Synopsis

     type
       MedBool = Boolean attribute (Size = BitSizeOf (MedInt));

Description

The intrinsic MedBool represents boolean values, but occupies the same memory space as a MedInt. It is used when you need to define a parameter or record that conforms to some external library or system specification.

Conforming to

MedBool is a GNU Pascal extension.

Example

     program MedBoolDemo;
     var
       a: MedBool;
     begin
       MedInt (a) := 1;
       if a then WriteLn ('Ord (True) = 1')
     end.

See also

Boolean (Intrinsic), Boolean, True, False, CBoolean, ByteBool, ShortBool, WordBool, LongBool, LongestBool.

Node: MedCard, Next: , Previous: MedBool, Up: Reference

MedCard

Synopsis

     type
       MedCard = Cardinal attribute (Size = BitSizeOf (MedInt));

Description

MedCard is an unsigned integer type which is not smaller than Cardinal. On most platforms it actually is the same as Cardinal and 32 bits wide and thus has a range of 0..4294967295.

MedCard in GNU Pascal is compatible to long unsigned int in GNU C. This compatibility is the reason why MedCard exists.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

MedCard is a GNU Pascal extension.

Example

     program MedCardDemo;
     var
       a: MedCard;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: MedInt, Next: , Previous: MedCard, Up: Reference

MedInt

Synopsis

     type
       MedInt  { built-in type }

Description

MedInt is a signed integer type which is not smaller than Integer. On most platforms it actually is the same as Integer and 32 bits wide and thus has a range of -2147483648..2147483647.

MedInt in GNU Pascal is compatible to long int in GNU C. This compatibility is the reason why MedInt exists.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

MedInt is a GNU Pascal extension.

Example

     program MedIntDemo;
     var
       a: MedInt;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: MedReal, Next: , Previous: MedInt, Up: Reference

MedReal

(Under construction.)

Synopsis

     type
       MedReal = Real;

Description

Conforming to

MedReal is a GNU Pascal extension.

Example

     program MedRealDemo;
     var
       a: MedReal;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Node: MedWord, Next: , Previous: MedReal, Up: Reference

MedWord

Synopsis

     type
       MedWord = MedCard;

Description

MedWord is an unsigned integer type which is not smaller than Word. On most platforms it actually is the same as Word and 32 bits wide and thus has a range of 0..4294967295. It is the same as MedCard.

MedWord in GNU Pascal is compatible to long unsigned int in GNU C. This compatibility is the reason why MedWord exists.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

MedWord is a GNU Pascal extension.

Example

     program MedWordDemo;
     var
       a: MedWord;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: Min, Next: , Previous: MedWord, Up: Reference

Min

(Under construction.)

Synopsis

     function Min (x1, x2: ordinal_or_real_type): same_type;

Description

Conforming to

Min is a GNU Pascal extension.

Example

See also

Node: MinReal, Next: , Previous: Min, Up: Reference

MinReal

(Under construction.)

Synopsis

Description

Conforming to

MinReal is an ISO 10206 Extended Pascal extension.

Example

See also

MaxReal.

Node: MkDir, Next: , Previous: MinReal, Up: Reference

MkDir

Synopsis

     procedure MkDir (Directory: String);

Description

MkDir creates the given Directory, if its argument is a valid parameter to the related operating system's function. Otherwise a runtime error is caused.

Conforming to

MkDir is a Borland Pascal extension.

Example

     program MkDirDemo;
     var
       Foo: String (127);
     begin
       WriteLn ('Enter directory name to create:');
       ReadLn (Foo);
       {$I-}  { Don't abort program on error }
       MkDir (Foo);
       if IOResult <> 0 then
         WriteLn ('Directory `', Foo, ''' could not be created')
       else
         WriteLn ('Okay')
     end.

See also

ChDir, RmDir

Node: mod, Next: , Previous: MkDir, Up: Reference

mod

(Under construction.)

Synopsis

     operator mod (p, q: Integer) = r: Integer;

Description

Integer remainder operator.

Conforming to

mod is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Keywords.

Node: module, Next: , Previous: mod, Up: Reference

module

(Under construction.)

Synopsis

Description

EP style or PXSC style module.

Conforming to

module is an ISO 10206 Extended Pascal extension.

Example

See also

Keywords.

Node: Move, Next: , Previous: module, Up: Reference

Move

(Under construction.)

Synopsis

     procedure Move (const Source; var Dest; Count: Integer);

Description

Conforming to

Move is a Borland Pascal extension.

Example

See also

Node: MoveLeft, Next: , Previous: Move, Up: Reference

MoveLeft

(Under construction.)

Synopsis

     procedure MoveLeft (const Source; var Dest; Count: Integer);

Description

Conforming to

MoveLeft is a UCSD Pascal extension.

Example

See also

Node: MoveRight, Next: , Previous: MoveLeft, Up: Reference

MoveRight

(Under construction.)

Synopsis

     procedure MoveRight (const Source; var Dest; count: Integer);

Description

Conforming to

MoveRight is a UCSD Pascal extension.

Example

See also

Node: name, Next: , Previous: MoveRight, Up: Reference

name

(Under construction.)

Synopsis

procedure/function_header; external name name;

procedure/function_header; attribute (name = name);

or

variable_declaration; external name name;

variable_declaration; attribute (name = name);

or

unit Name; attribute (name = name);

Description

The name directive declares the external name of a procedure, function or variable. It can be used after external or within attribute.

This directive declares the external name of a procedure, function or variable. The external name of the routine is given explicitly as a case-sensitive constant string expression. This is useful when interfacing with libraries written in other languages.

With this extension it is possible to access all external functions, for example the X11 interface functions, and not only those written in lowercase.

name can also be applied to units and module interfaces. In this case it denotes the prefix prepended to the external name of the initializer of the unit: While it is normally called init_Modulename, it is called init_name_Modulename when name is given.

This is not of interest under normal circumstances since the initializers are called automatically. It can help avoiding conflicts when there are several units of the same name within one program. Again, this does not happen normally, but e.g., when a program uses a unit/module that has the same name as one of the units the RTS consists of: The RTS uses GPC as the name for its units to avoid conflicts.

In the future, a name directive applied to units, modules and programs (the latter is recognized syntactically already, but has no effect yet) will also affect the default external name of routines and variables which have no name directive themselves. Again, this is mostly useful for libraries etc., and will not be necessary for normal units, modules and programs.

Conforming to

name is a Borland Pascal extension. attribute and the application of name to units, modules and programs are GNU Pascal extensions.

Example

     program NameDemo;
     
     { Make two variables aliases of each other by using `name'.
       This is not good style. If you must have aliases for any reason,
       `absolute' declarations may be the lesser evil ... }
     var
       Foo: Integer; attribute (name = 'Foo_Bar');
       Bar: Integer; external name 'Foo_Bar';
     
     { A function from the C library }
     function PutS (Str: CString): Integer; external name 'puts';
     
     var
       Result: Integer;
     begin
       Result := PutS ('Hello World!');
       WriteLn ('puts wrote ', Result, ' characters (including a newline).');
       Foo := 42;
       WriteLn ('Foo = ', Foo);
       Bar := 17;
       WriteLn ('Setting Bar to 17.');
       WriteLn ('Now, Foo = ', Foo, '!!!')
     end.

See also

Keywords, attribute, external, Importing Libraries from Other Languages.

Node: NE, Next: , Previous: name, Up: Reference

NE

(Under construction.)

Synopsis

     function NE (S1, S2: String): Boolean;

Description

Conforming to

NE is an ISO 10206 Extended Pascal extension.

Example

See also

Node: near, Next: , Previous: NE, Up: Reference

near

Synopsis

Description

The near directive can be appended to a procedure or function heading but is ignored by GPC. It is there for Borland compatibility, only. (Since the GNU compilers provide a flat memory model, the distinction between near and far pointers is void.)

Conforming to

near is a Borland Pascal extension.

Example

     program NearDemo;
     
     var
       p: procedure;
     
     {$W no-near-far}  { Don't warn about the uselessness of `near' }
     
     procedure Foo; near;  { `near' has no effect in GPC }
     begin
       WriteLn ('Foo')
     end;
     
     begin
       p := Foo;  { Works, despite the `near'. }
       p
     end.

See also

Keywords, far.

Node: NEPad, Next: , Previous: near, Up: Reference

NEPad

(Under construction.)

Synopsis

     function NEPad (S1, S2: String): Boolean;

Description

Conforming to

NEPad is a GNU Pascal extension.

Example

See also

Node: New, Next: , Previous: NEPad, Up: Reference

New

(Under construction.)

Synopsis

     procedure New (var P: any_Pointer);
or 
     procedure New (var P: Pointer_to_a_variant_record; tag_fields);
or 
     procedure New (var P: Pointer_to_a_schema; discriminants);
or 
     procedure New (var P: Pointer_to_an_object; constructor_call);
or 
     function New (any_Pointer_type): same_type;
or 
     function New (variant_record_Pointer_type;
                   tag_fields): same_type;
or 
     function New (schema_Pointer_type;
                   discriminants): same_type;
or 
     function New (object_Pointer_type;
                   constructor_call): same_type;

Description

Conforming to

New is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Node: NewCString, Next: , Previous: New, Up: Reference

NewCString

(Under construction.)

Synopsis

     function NewCString (const S: String): CString;

Description

Conforming to

NewCString is a GNU Pascal extension.

Example

See also

Node: nil, Next: , Previous: NewCString, Up: Reference

nil

Synopsis

nil is a predefined constant

Description

nil is a predefined pointer constant that indicates an unassigned pointer. "nil" stands for "not in list". Every pointer type can be associated with this constant.

Conforming to

nil is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program NilDemo;
     const
       NodeNum = 10;
     type
       PNode = ^TNode;
       TNode = record
         Key: Integer;
         Next: PNode
       end;
     var
       Root, Node: PNode;
       Foo: Integer;
     begin
       New (Root);
       Root^.Key := 1;             { Set root key }
       Node := Root;
       for Foo := 2 to NodeNum do  { Create linked list with NODE_NUM nodes }
         begin
           New (Node^.Next);
           Node := Node^.Next;
           Node^.Key := Foo        { Set key }
         end;
       Node^.Next := nil;          { Mark end of linked list }
       { Shorten list by removing its first element until list is empty }
       while Root <> nil do
         begin
           Node := Root;
           WriteLn ('Current key:', Root^.Key);
           Root := Root^.Next;
           Dispose (Node);
           Node := nil             { Indicate old node is not assigned }
         end
     end.

See also

Keywords, Assigned, Pointer

Node: not, Next: , Previous: nil, Up: Reference

not

(Under construction.)

Synopsis

     operator not (b1, b2: Boolean) = Result: Boolean;
or 
     operator not (i1, i2: integer_type) = Result: integer_type;

Description

Boolean or bitwise negation operator.

Conforming to

not is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Keywords.

Node: Null, Next: , Previous: not, Up: Reference

Null

Synopsis

     var
       Null: Void absolute 0;

Description

Null is a predefined variable at address nil. Null can be passed as a "void" argument to a procedure, function or operator expecting a "var" parameter. Note: Make sure they can handle this case, otherwise this is likely to cause an exception and the program will be terminated. Since Null is an L-value, it can be taken as "nil-reference".

Conforming to

Null is a Borland Delphi extension.

Example

     program NullDemo;
     type
       PString = ^String;
     var
       Com1: String (25) = 'This is an amazing number';
       Com2: String (25) = 'This is a boring number';
     
     procedure FooBar (Foo: Integer; var Comment: PString);
     begin
       if Odd (Foo) then
         WriteLn ('FooBar:', Foo, ' is odd')
        else
         WriteLn ('FooBar:', Foo, ' is even');
       if @Comment <> nil then
         if not Odd (Foo) then
           Comment := @Com1
         else
           Comment := @Com2
     end;
     
     var
       S: String (25);
       P: PString value @S;
     
     begin
       { FooBar allows you to leave out variables
         for any information you might not need }
       FooBar (1, Null);
       { But FooBar is flexible, after all }
       FooBar (6, P);
       WriteLn ('FooBar said about 6: `', P^, '''')
     end.

See also

nil

Node: object, Next: , Previous: Null, Up: Reference

object

Synopsis

Description

The keyword object is used to declare a new object type: 

     type
       foo = object
         a: Integer;
         constructor Init;
         procedure Bar (x: Integer); virtual;
       end;

(For a longer example, see OOP.)

Conforming to

GNU Pascal follows the Borland Pascal 7.0 object model.

ISO Pascal does not support Object-oriented programming. There is an ANSI draft for an "Object Pascal" language which is not yet supported by GPC, but planned. The Delphi language, also called "Object Pascal" by Borland, is currently not supported by GPC either.

Example

See also

Keywords, OOP, record.

Node: Odd, Next: , Previous: object, Up: Reference

Odd

Synopsis

     function Odd (i: Integer): Boolean;

Description

Odd checks the parity of its argument i. It returns True if the argument is odd, False if it is even.

Conforming to

Odd is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program OddDemo;
     var
       Foo: Integer;
     begin
       Write ('Please enter an odd number: ');
       ReadLn (Foo);
       if not Odd (Foo) then
         WriteLn ('Odd''s not even! Something''s odd out there ...')
       else
         WriteLn (Foo, ' is pretty odd.')
     end.

See also

Node: of, Next: , Previous: Odd, Up: Reference

of

(Under construction.)

Synopsis

Description

Part of an array, set or typed file type declaration, a case statement, a variant record type or a type of type inquiry.

Conforming to

of is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Keywords.

Node: only, Next: , Previous: of, Up: Reference

only

(Under construction.)

Synopsis

Description

Import specification.

Conforming to

only is an ISO 10206 Extended Pascal extension.

Example

See also

Keywords.

Node: operator, Next: , Previous: only, Up: Reference

operator

(Under construction.)

Synopsis

Description

Operator declaration.

Conforming to

operator is PASCAL_SC extension.

Example

See also

Keywords.

Node: or, Next: , Previous: operator, Up: Reference

or

Synopsis

     operator or (operand1, operand2: Boolean) = Result: Boolean;
or 
     operator or (operand1, operand2: integer_type) = Result: integer_type;
or 
     procedure or (var operand1: integer_type; operand2: integer_type);

Description

In GNU Pascal, or has three built-in meanings:

  1. Logical "or" between two Boolean-type expressions. The result of the operation is of Boolean type.

    By default, or acts as a short-circuit operator in GPC: If the first operand is True, the second operand is not evaluated because the result is already known to be True. You can change this to complete evaluation using the --no-short-circuit command-line option or the {$B+} compiler directive.

  2. Bitwise "or" between two integer-type expressions. The result is of the common integer type of both expressions.
  3. Use as a "procedure": operand1 is "or"ed bitwise with operand2; the result is stored in operand1.

Conforming to

The logical or operator is defined in ISO 7185 Pascal.

According to ISO, you cannot rely on or being a short-circuit operator. On the other hand, GPC's default behaviour does not contradict the ISO standard. (See or_else.) However, since it seems to be a de-facto standard among ISO Pascal compilers to evaluate both operands of or, GPC switches to --no-short-circuit mode if one of the language dialect options selecting ISO Pascal, for instance --extended-pascal, is given. Use --short-circuit to override.

Use of or as a bitwise operator for integers is a Borland Pascal extension.

Use of or as a "procedure" is a GNU Pascal extension.

Example

     program OrDemo;
     var
       a, b, c: Integer;
     begin
       if (a = 0) or (b = 0) then  { logical `or' }
         c := 1
       else if (a or b) = 0 then  { bitwise `or' }
         c := 2
       else
         or (c, a)  { same as `c := c or a' }
     end.

Note the difference between the logical or and the bitwise or: When a is 2 and b is 4, then a or b is 6. Beware: a or b = 0 happens to mean the same as (a = 0) and (b = 0). (Note the and!)

Since bitwise or has a higher priority than the = operator, parentheses are needed in if (a = 0) or (b = 0) because otherwise 0 or b would be calculated first, and the remainder would cause a parse error.

See also

Keywords, and, xor, Operators.

Node: Ord, Next: , Previous: or, Up: Reference

Ord

Synopsis

     function Ord (ordinal_value): Integer;

Description

Ord returns the ordinal value of any ordinal variable or constant. For characters, this would be the ASCII code corresponding to the character. For enumerated types, this would be the ordinal value of the constant or variable (remember that ordinal value of enumerated constants start from zero).

Conforming to

Ord is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program OrdDemo;
     var
       Ch: Char;
       Day: (Monday, Tuesday, Wednesday, Thursday, Friday);
     begin
       Ch := 'A';
       WriteLn (Ord (Ch));  { 65 }
       Day := Thursday;
       WriteLn (Ord (Day));  { 3 }
     end.

See also

Character Types, Ordinal Types, Chr, Char

Node: or else, Next: , Previous: Ord, Up: Reference

or else

Synopsis

     { `or else' is built in. A user-defined operator cannot consist of
        two words. }
     operator or else (operand1, operand2: Boolean) = Result: Boolean;

Description

or else is an alias for the short-circuit logical operator or_else.

Conforming to

While or_else is defined in ISO 10206 Extended Pascal, or else is a GNU Pascal extension.

Example

     program OrElseDemo;
     var
       a: Integer;
     begin
       ReadLn (a);
       if (a = 0) or else (100 div a > 42) then  { This is safe. }
         WriteLn ('100 div a > 42')
     end.

See also

Keywords, or_else, or, and then.

Node: or_else, Next: , Previous: or else, Up: Reference

or_else

Synopsis

     operator or_else (operand1, operand2: Boolean) = Result: Boolean;

Description

The or_else short-circuit logical operator performs the same operation as the logical operator or. But while the ISO standard does not specify anything about the evaluation of the operands of or - they may be evaluated in any order, or not at all - or_else has a well-defined behaviour: It evaluates the first operand. If the result is True, or_else returns True without evaluating the second operand. If it is False, the second operand is evaluated and returned.

GPC by default treats or and or_else exactly the same. If you want, for some reason, to have both operands of or evaluated completely, you must assign both to temporary variables and then use or - or or_else, it does not matter.

Conforming to

or_else is an ISO 10206 Extended Pascal extension.

Some people think that the ISO standard requires both operands of or to be evaluated. This is false. What the ISO standard does say is that you cannot rely on a certain order of evaluation of the operands of or; in particular things like the following program can crash according to ISO Pascal, although they cannot crash when compiled with GNU Pascal running in default mode. 

     program OrBug;
     var
       a: Integer;
     begin
       ReadLn (a);
       if (a = 0) or (100 div a > 42) then  { This is *not* safe! }
         WriteLn ('You''re lucky. But the test could have crashed ...')
     end.

Example

     program Or_ElseDemo;
     var
       a: Integer;
     begin
       ReadLn (a);
       if (a = 0) or_else (100 div a > 42) then  { This is safe. }
         WriteLn ('100 div a > 42')
     end.

See also

Keywords, or else, or, and_then.

Node: otherwise, Next: , Previous: or_else, Up: Reference

otherwise

Synopsis

Default case branch as part of the case ... otherwise statement: 

     case expression of
       selector: statement;
       ...
       selector: statement
     otherwise  { ``else'' instead of ``otherwise'' is allowed }
       statement;
       ...
       statement
     end

Description

otherwise starts a series of statements which is executed if no selector matches expression. In this situation, else is a synonym for otherwise.

Conforming to

otherwise is an ISO 10206 Extended Pascal extension.

Example

See case.

See also

Keywords, case Statement, case, else.

Node: Output, Next: , Previous: otherwise, Up: Reference

Output

(Under construction.)

Synopsis

     var
       Output: Text;

Description

Conforming to

Output is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Node: Pack, Next: , Previous: Output, Up: Reference

Pack

(Under construction.)

Synopsis

Description

     procedure Pack (Source: unpacked_array;
                     FirstElement: index_type;
                     var Dest: packed_array);

Conforming to

Pack is defined in ISO 7185 Pascal and supported by all known Pascal variants except UCSD/Borland Pascal and its variants.

Example

See also

Node: packed, Next: , Previous: Pack, Up: Reference

packed

Synopsis

Description

packed is a reserved word. According to ISO 7185 Pascal it can precede array and record type definitions to indicate that memory usage should be minimized for variables of this type, possibly at the expense of loss of speed.

As a GNU Pascal extension, packed can also be applied to Subrange Types.

Conforming to

The reserved word packed is defined in ISO 7185 Pascal.

According to ISO standard, only packed arrays of char with lower bound 1 qualify as strings of fixed length. GNU Pascal neither requires packed nor the lower bound of 1 here.

Example

     program PackedDemo;
     
     type
       MonthInt = packed 1 .. 12;  { needs one byte }
       FastMonthInt = 1 .. 12;     { needs e.g. four bytes }
     
       FixString10 = packed array [1 .. 10] of Char;
       FoxyString10 = array [0 .. 9] of Char;
     
       Flags = packed array [1 .. 32] of Boolean;  { needs four bytes }
     
       Int15 = Integer attribute (Size = 15);
       DateRec = packed record
         Day: 1 .. 31;       { five bits }
         Month: MonthInt;    { four bits }
         Year: Int15         { 15 bits = -16384 .. 16383 }
       end;
     
       Dates = array [1 .. 1000] of DateRec;
     
     var
       S: FixString10;
       T: FoxyString10;
     
     begin
       S := 'Hello!';  { blank padded }
       WriteLn (S);
     
       T := 'GNU Pascal';  { GPC extension: this also works. }
       WriteLn (T)
     end.

DateRec has 24 bits = 3 bytes in total; Dates has 3000 bytes.

See also

Keywords, Pack, Unpack, SizeOf, AlignOf, BitSizeOf.

Node: Page, Next: , Previous: packed, Up: Reference

Page

(Under construction.)

Synopsis

     procedure Page ([var F: Text]);
or 
     procedure Page;

Description

Conforming to

Page is an ISO 10206 Extended Pascal extension.

Example

See also

Node: PAnsiChar, Next: , Previous: Page, Up: Reference

PAnsiChar

(Under construction.)

Synopsis

     type
       PAnsiChar = ^AnsiChar;

Description

Conforming to

PAnsiChar is a Borland Delphi extension.

Example

     program PAnsiCharDemo;
     var
       s: PAnsiChar;
     begin
       s := 'Hello, world!';
       {$X+}
       WriteLn (s)
     end.

See also

Node: ParamCount, Next: , Previous: PAnsiChar, Up: Reference

ParamCount

Synopsis

     function ParamCount: Integer;

Description

ParamCount returns the number of command-line arguments given to the program. ParamCount returns 0 if no arguments have been given to the program; the name of the program as an implicit argument is not counted.

Conforming to

ParamCount is a Borland Pascal extension.

Example

     program ParamCountDemo;
     
     var
       i: Integer;
     
     begin
       WriteLn ('You have invoked this program with ',
                ParamCount, ' arguments.');
       WriteLn ('These are:');
       for i := 1 to ParamCount do
         WriteLn (ParamStr (i))
     end.

See also

ParamStr.

Node: ParamStr, Next: , Previous: ParamCount, Up: Reference

ParamStr

(Under construction.)

Synopsis

     function ParamStr (ParmNumber: Integer): String;

Description

Please note: If you are using the Dos (DJGPP) or MS-Windows (mingw32) version of GPC and are getting unexpected results from ParamStr, please see the section "Command-line Arguments Handling in DJGPP" of the DJGPP FAQ list.

Conforming to

ParamStr is a Borland Pascal extension.

Example

     program ParamStrDemo;
     
     var
       i: Integer;
     
     begin
       WriteLn ('You have invoked this program with ',
                ParamCount, ' arguments.');
       WriteLn ('These are:');
       for i := 1 to ParamCount do
         WriteLn (ParamStr (i))
     end.

See also

Node: PChar, Next: , Previous: ParamStr, Up: Reference

PChar

(Under construction.)

Synopsis

     type
       PChar = ^Char;
or 
     type
       PChar = CString;

Description

Conforming to

PChar is a Borland Pascal extension.

Example

     program PCharDemo;
     var
       s: PChar;
     begin
       s := 'Hello, world!';
       {$X+}
       WriteLn (s)
     end.

See also

Node: Pi, Next: , Previous: PChar, Up: Reference

Pi

(Under construction.)

Synopsis

Description

Conforming to

Pi is a Borland Pascal extension.

Example

See also

Node: PObjectType, Next: , Previous: Pi, Up: Reference

PObjectType

Synopsis

     type
       InternalSignedSizeType = Integer attribute (Size = BitSizeOf (SizeType));
       PObjectType = ^const record
         Size:        SizeType;
         NegatedSize: InternalSignedSizeType;
         Parent:      PObjectType;
         Name:        ^const String
       end;

(Note: ^record is not valid syntax. It is just used here in the explanation because the record type has no name by itself. Because of the added method pointers (see below), there is no useful usage of the record type.)

Description

PObjectType is the type returned by TypeOf and required by SetType. In fact, the record pointed to (the VMT, "virtual method table") also contains pointers to the virtual methods. However, these are not declared in PObjectType because they vary from object type to object type. The fields declared here are those that are shared by every object type and can be accessed via TypeOf.

Size contains the size of the object type, NegatedSize contains the size negated (for runtime checks). Parent contains a pointer to the parent type's VMT (or nil if the type has no parent). Name points to a string containing the type's name.

Conforming to

PObjectType is a GNU Pascal extension.

Example

See also

TypeOf, SetType, OOP.

Node: Pointer, Next: , Previous: PObjectType, Up: Reference

Pointer

(Under construction.)

Synopsis

     type
       Pointer  { built-in type }

Description

Conforming to

Pointer is a Borland Pascal extension.

Example

     program PointerDemo;
     var
       a: Integer;
       b: Boolean;
       p: Pointer;
     begin
       p := nil;
       p := @a;
       p := @b
     end.

See also

Node: Polar, Next: , Previous: Pointer, Up: Reference

Polar

(Under construction.)

Synopsis

     function Polar (rho, phi: Real): Complex;

Description

Conforming to

Polar is an ISO 10206 Extended Pascal extension.

Example

See also

Node: Pos, Next: , Previous: Polar, Up: Reference

Pos

(Under construction.)

Synopsis

     function Pos (SearchPattern, Source: String): Integer;

Description

Conforming to

Pos is a UCSD Pascal extension.

Example

See also

Node: Position, Next: , Previous: Pos, Up: Reference

Position

(Under construction.)

Synopsis

     function Position (var F: typed_file);

Description

Conforming to

Position is an ISO 10206 Extended Pascal extension.

Example

See also

Node: pow, Next: , Previous: Position, Up: Reference

pow

(Under construction.)

Synopsis

     operator pow (base: Real; exponent: Integer) = power: Real;
or 
     operator pow (base: Complex; exponent: Integer) = power: Complex;

Description

Exponentiation operator with integer exponent.

Conforming to

pow is an ISO 10206 Extended Pascal extension.

Example

See also

Keywords.

Node: Pred, Next: , Previous: pow, Up: Reference

Pred

Synopsis

     function Pred (i: ordinal_type): ordinal_type;
or 
     function Pred (i: ordinal_type; j: Integer): ordinal_type;

or, with extended syntax (--extended-syntax or {$X+}), 

     function Pred (p: Pointer_type): Pointer_type;
or 
     function Pred (p: Pointer_type; j: Integer): Pointer_type;

Description

Returns the predecessor of the ordinal_type value i, or, if the second argument j is given, its jth predecessor. For integer values i, this is i - 1 (or i - j). (No, Pred does not work faster than plain subtraction. Both are optimized the same way, often to a single machine instruction.)

If extended syntax is on, the argument may also be a pointer value. In this case, the address is decremented by the size of the variable pointed to, or, if j is given, by j times the size of the variable pointed to. If p points to an element of an array, the returned pointer will point to the (jth) previous element of the array.

Conforming to

The Pred function is defined in ISO 7185 Pascal. The optional second parameter is defined in ISO 10206 Extended Pascal. Application of Pred to pointers is defined in Borland Pascal. The combination of the second argument with application to pointers is a GNU Pascal extension.

Example

     program PredDemo;
     
     type
       Metasyntactical = (foo, bar, baz);
     
     var
       m: Metasyntactical;
       c: Char;
       a: array [1 .. 7] of Integer;
       p: ^Integer;
     
     begin
       m := Pred (bar);     { foo }
       c := Pred ('Z', 2);  { 'X' }
       a[1] := 42;
       a[4] := Pred (a[1]);     { 41 }
       a[5] := Pred (a[4], 3);  { 38 }
       {$X+}
       p := @a[5];
       p := Pred (p);     { now p points to a[4] }
       p := Pred (p, 3);  { now p points to a[1] }
     end.

See also

Succ, Dec, Pointer Arithmetics.

Node: private, Next: , Previous: Pred, Up: Reference

private

(Under construction.)

Synopsis

Description

GPC currently accepts but ignores the private directive in object type declarations.

Conforming to

private is a Borland Pascal extension.

Example

See also

Keywords, protected, public, published.

Node: procedure, Next: , Previous: private, Up: Reference

procedure

(Under construction.)

Synopsis

Description

Procedure declaration.

Conforming to

procedure is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Keywords.

Node: program, Next: , Previous: procedure, Up: Reference

program

(Under construction.)

Synopsis

Description

Start of a Pascal program.

Conforming to

program is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Keywords.

Node: property, Next: , Previous: program, Up: Reference

property

Not yet implemented.

Synopsis

Description

Object properties.

Conforming to

property is an Object Pascal and a Borland Delphi extension.

Example

See also

Keywords.

Node: protected, Next: , Previous: property, Up: Reference

protected

(Under construction.)

Synopsis

Description

The Extended Pascal meaning of protected is supported by GPC.

GPC currently accepts but ignores the protected directive in object type declarations.

Conforming to

Extended Pascal and Borland Pascal, but with different meanings.

Example

See also

Keywords, const, import, private, public, published.

Node: PtrCard, Next: , Previous: protected, Up: Reference

PtrCard

(Under construction.)

Synopsis

     type
       PtrCard = Cardinal attribute (Size = BitSizeOf (Pointer));

Description

An unsigned integer type of the same size as a pointer.

Conforming to

PtrCard is a GNU Pascal extension.

Example

     program PtrCardDemo;
     var
       a: PtrCard;
       p: Pointer;
     begin
       GetMem (p, 10);
       a := PtrCard (p);
       Inc (a);
       p := Pointer (a)
     end.

See also

Node: PtrDiffType, Next: , Previous: PtrCard, Up: Reference

PtrDiffType

(Under construction.)

Synopsis

     type
       PtrDiffType  { built-in type }

Description

PtrDiffType is a (signed) integer type to represent the difference between two positions in memory. It is not needed except for rather low-level purposes.

Conforming to

PtrDiffType is a GNU Pascal extension.

Example

     program PtrDiffTypeDemo;
     var
       a: array [1 .. 10] of Integer;
       d: PtrDiffType;
       p, q: ^Integer;
     begin
       p := @a[1];
       q := @a[4];
       {$X+}
       d := q - p
     end.

See also

Node: PtrInt, Next: , Previous: PtrDiffType, Up: Reference

PtrInt

(Under construction.)

Synopsis

     type
       PtrCard = Integer attribute (Size = BitSizeOf (Pointer));

Description

A signed integer type of the same size as a pointer.

Conforming to

PtrInt is a GNU Pascal extension.

Example

     program PtrIntDemo;
     var
       a: PtrInt;
       p: Pointer;
     begin
       GetMem (p, 10);
       a := PtrInt (p);
       Inc (a);
       p := Pointer (a)
     end.

See also

Node: PtrWord, Next: , Previous: PtrInt, Up: Reference

PtrWord

(Under construction.)

Synopsis

     type
       PtrWord = PtrCard;

Description

An unsigned integer type of the same size as a pointer.

Conforming to

PtrWord is a GNU Pascal extension.

Example

     program PtrWordDemo;
     var
       a: PtrWord;
       p: Pointer;
     begin
       GetMem (p, 10);
       a := PtrWord (p);
       Inc (a);
       p := Pointer (a)
     end.

See also

Node: public, Next: , Previous: PtrWord, Up: Reference

public

(Under construction.)

Synopsis

Description

GPC currently accepts but ignores the public directive in object type declarations.

Conforming to

public is a Borland Pascal extension.

Example

See also

Keywords, private, protected, published.

Node: published, Next: , Previous: public, Up: Reference

published

(Under construction.)

Synopsis

Description

GPC currently accepts but ignores the published directive in object type declarations.

Conforming to

published is a Borland Delphi extension.

Example

See also

Keywords, private, protected, public.

Node: Put, Next: , Previous: published, Up: Reference

Put

(Under construction.)

Synopsis

     procedure Put (var F: typed_file);

Description

Conforming to

Put is defined in ISO 7185 Pascal and supported by all known Pascal variants except UCSD/Borland Pascal and its variants.

Example

See also

Node: qualified, Next: , Previous: Put, Up: Reference

qualified

(Under construction.)

Synopsis

Description

Import specification.

Conforming to

qualified is an ISO 10206 Extended Pascal extension.

Example

See also

Keywords.

Node: Random, Next: , Previous: qualified, Up: Reference

Random

(Under construction.)

Synopsis

Description

Conforming to

Random is a UCSD Pascal extension.

Example

See also

Node: Randomize, Next: , Previous: Random, Up: Reference

Randomize

(Under construction.)

Synopsis

Description

Conforming to

Randomize is a UCSD Pascal extension.

Example

See also

Node: Re, Next: , Previous: Randomize, Up: Reference

Re

Synopsis

     function Re (z: Complex): Real;

Description

Re extracts the real part of the complex number z.

Conforming to

Re is an ISO 10206 Extended Pascal extension.

Example

     program ReDemo;
     var
       z: Complex;
     begin
       z := Cmplx (1, 2);
       WriteLn (Re (z) : 0 : 5)
     end.

See also

Cmplx, Im, Arg

Node: Read, Next: , Previous: Re, Up: Reference

Read

(Under construction.)

Synopsis

     procedure Read (var F: typed_file; variable);
or 
     procedure Read (var F: Text; variables);
or 
     procedure Read (variables);

Description

Conforming to

Read is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Node: ReadLn, Next: , Previous: Read, Up: Reference

ReadLn

(Under construction.)

Synopsis

     procedure ReadLn (var F: Text; variables);
or 
     procedure ReadLn (variables);

Description

Conforming to

ReadLn is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Node: ReadStr, Next: , Previous: ReadLn, Up: Reference

ReadStr

(Under construction.)

Synopsis

     procedure ReadStr (const S: String; variables);

Description

Conforming to

ReadStr is an ISO 10206 Extended Pascal extension.

Example

See also

Node: Real, Next: , Previous: ReadStr, Up: Reference

Real

(Under construction.)

Synopsis

     type
       Real  { built-in type }

Description

Conforming to

Real is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program RealDemo;
     var
       a: Real;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Real Types, Int, Frac, Round, Trunc.

Node: record, Next: , Previous: Real, Up: Reference

record

Synopsis

In type definitions: 

     record_type_identifier = record
       field_identifier: type_definition
       ...
       field_identifier: type_definition
     end;

or, with a variant part, 

     record_type_identifier = record
       field_identifier: type_definition
       ...
       field_identifier: type_definition
       case bar: variant_type of
         selector: (field_declarations);
         selector: (field_declarations);
         ...
     end;

or, without a variant selector field, 

     record_type_identifier = record
       field_identifier: type_definition
       ...
       field_identifier: type_definition
       case variant_type of
         selector: (field_declarations);
         selector: (field_declarations);
         ...
     end;

Description

The reserved word record starts the definition of a new record type.

Records can be packed to save memory usage at the expense of speed.

The variants of a variant record may - but are not required to - share one location in memory (inside the record).

Sometimes variant records are used to emulate type casting in ISO 7185 Pascal. This is in fact a violation of the standard and not portable. There is intentionally no possibility in ISO 7185 Pascal to emulate type casting.

Conforming to

The reserved word record and record types are defined in ISO 7185 Pascal.

According to ISO Pascal, the variant type must be an identifier. GNU Pascal, like UCSD and Borland Pascal, also allows a subrange here.

Subranges in the variant fields, e.g. case Integer of 2 .. 5, are a GPC extension.

Example

     program RecordDemo;
     
     type
       FooPtr = ^Foo;
     
       Foo = record
         Bar: Integer;
         NextFoo: FooPtr;
         case Choice: 1 .. 3 of
           1: (a: Integer);  { These three choices may share }
           2: (b: Real);     { one location in memory. }
           3: (c: Char;
               d: Boolean);
       end;
     
       Int5 = Integer attribute (Size = 5);
       SmallFoo = packed record
         b: 0 .. 3;
         a: Int5;
         r: Boolean
       end;  { needs 1 byte }
     
     var
       f: Foo;
     
     begin
       f.b := 3.14;
       WriteLn (f.a)  { yields some strange number which is part of the   }
                      { internal representation of the real number `f.b'. }
     end.

See also

Keywords, packed, case Statement

Node: Release, Next: , Previous: record, Up: Reference

Release

(Under construction.)

Synopsis

     procedure Release (P: Pointer);

Description

Conforming to

Release is a UCSD Pascal extension.

Example

See also

Node: Rename, Next: , Previous: Release, Up: Reference

Rename

(Under construction.)

Synopsis

     procedure Rename (var F: any_file; NewName: String);

Description

Conforming to

Rename is a Borland Pascal extension.

Example

See also

Node: repeat, Next: , Previous: Rename, Up: Reference

repeat

Synopsis

     repeat
       statement;
       ...
       statement;
     until boolean_expression;

Description

The repeat ... until statement declares a loop. For further description see repeat Statement.

Conforming to

repeat is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program RepeatDemo;
     var
       Number, Sum: Integer;
     begin
       WriteLn ('Black Jack for beginners.');
       WriteLn ('You can choose your cards yourself. :-)');
       Sum := 0;
       repeat
         Write ('Your card (number)? ');
         ReadLn (Number);
         Inc (Sum, Number);
         WriteLn ('You have ', Sum, '.')
       until Sum >= 21;
       if Sum = 21 then
         WriteLn ('You win!')
       else
         WriteLn ('You lose.')
     end.

See also

Keywords, while Statement, for Statement.

Node: Reset, Next: , Previous: repeat, Up: Reference

Reset

(Under construction.)

Synopsis

     procedure Reset (var F: any_file; [FileName: String;]
                                         [BlockSize: Cardinal]);

Description

Reset opens an existing file for reading. The file pointer is positioned at the beginning of the file.

Like Rewrite, Append and Extend do, Reset accepts an optional second and third parameter for the name of the file in the filesystem and, for untyped files, the block size of the file. (For details, see Rewrite.)

Conforming to

Reset is defined in ISO 7185 Pascal. The BlockSize parameter is a Borland Pascal extension. The FileName parameter is a GNU Pascal extension.

Example

     program ResetDemo;
     var
       Sample: Text;
       s: String (42);
     begin
       Rewrite (Sample);  { Open an internal file for writing }
       WriteLn (Sample, 'Hello, World!');
       Reset (Sample);  { Open it again for reading }
       ReadLn (Sample, s);
       WriteLn (s);
       Close (Sample)
     end.

See also

Assign, Rewrite, Append, Extend.

Node: resident, Next: , Previous: Reset, Up: Reference

resident

Not yet implemented.

Synopsis

Description

Library export specification.

Conforming to

resident is a Borland Pascal extension.

Example

See also

Keywords.

Node: restricted, Next: , Previous: resident, Up: Reference

restricted

(Under construction.)

Synopsis

Description

Restricted type specification.

Conforming to

restricted is an ISO 10206 Extended Pascal extension.

Example

See also

Keywords.

Node: Result, Next: , Previous: restricted, Up: Reference

Result

(Under construction.)

Synopsis

Description

Conforming to

Result is a Borland Delphi extension.

Example

See also

Node: Return, Next: , Previous: Result, Up: Reference

Return

(Under construction.)

Synopsis

Description

Conforming to

Return is a GNU Pascal extension.

Example

See also

Node: ReturnAddress, Next: , Previous: Return, Up: Reference

ReturnAddress

(Under construction.)

Synopsis

Description

Conforming to

ReturnAddress is a GNU Pascal extension.

Example

See also

Node: Rewrite, Next: , Previous: ReturnAddress, Up: Reference

Rewrite

(Under construction.)

Synopsis

     procedure Rewrite (var F: any_file; [FileName: String;]
                                         [BlockSize: Cardinal]);

Description

Rewrite opens a file for writing. If the file does not exist, it is created. The file pointer is positioned at the beginning of the file.

Like Reset, Append and Extend do, Rewrite accepts an optional second and third parameter.

The second parameter can specify the name of the file in the filesystem. If it is omitted, the following alternative ways can be used to specify the name. There are so many different ways in order to be compatible to the idiosyncrasies of as many other Pascal compilers as possible. (If you know about yet other ways, let us know ...)

The following ways are only available if the file is external, i.e. a global variable which is mentioned in the program header. Otherwise, the file will be internal, i.e. get no name in the file system (it may get a name temporarily, but will then be erased automatically again). This is useful to store some data and read them back within a program without the need for permanent storage.

The last optional parameter determines the block size of the file. It is valid only for untyped files. Almost always, 1 is the most reasonable value here. However, the existence of this parameter is a BP compatibility feature, and in BP it defaults to 128 because of historic misdesign. Therefore, GPC requires this parameter to be present. In --borland-pascal mode, it makes it optional (like BP does), but warns about the strange default if omitted.

Conforming to

Rewrite is defined in ISO 7185 Pascal. The BlockSize parameter is a Borland Pascal extension. The FileName parameter is a GNU Pascal extension.

Example

     program RewriteDemo;
     var
       Sample: Text;
     begin
       Assign (Sample, 'sample.txt');
       Rewrite (Sample);
       WriteLn (Sample, 'Hello, World!');
       Close (Sample)
     end.

See also

Assign, Reset, Append, Extend, Update.

Node: RmDir, Next: , Previous: Rewrite, Up: Reference

RmDir

Synopsis

     procedure RmDir (Directory: String);

Description

RmDir removes the given Directory if its argument is a valid parameter to the related operating system's function. Otherwise a runtime error is caused.

Conforming to

RmDir is a Borland Pascal extension.

Example

     program RmDirDemo;
     var
       Foo: String (127);
     begin
       WriteLn ('Enter directory name to remove: ');
       ReadLn (Foo);
       {$I-}  { Don't abort on I/O errors }
       RmDir (Foo);
       if IOResult <> 0 then
         WriteLn ('Directory ', Foo, ' could not be removed.')
       else
         WriteLn ('Okay.')
     end.

See also

ChDir, MkDir

Node: Round, Next: , Previous: RmDir, Up: Reference

Round

Synopsis

     function Round (x: Real): Integer;

Description

Round returns the nearest integer to x. The result is of type integer. In the case of equidistance, the result is machine-dependent (or depends on the behaviour of the processor).

Conforming to

Round is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program RoundDemo;
     var
       Foo: Real;
     begin
       Foo := 9.876543;
       WriteLn (Round (Foo));  { Prints 10 }
       Foo := 3.456789;
       WriteLn (Round (Foo));  { Prints 3 }
     
       WriteLn (Frac (12.345) : 1 : 5);  { 0.34500 }
       WriteLn (Int (12.345) : 1 : 5);  { 12.00000 }
       WriteLn (Round (12.345) : 1);  { 12 }
       WriteLn (Trunc (12.345) : 1);  { 12 }
     
       WriteLn (Frac (-12.345) : 1 : 5);  { -0.34500 }
       WriteLn (Int (-12.345) : 1 : 5);  { -12.00000 }
       WriteLn (Round (-12.345) : 1);  { -12 }
       WriteLn (Trunc (-12.345) : 1);  { -12 }
     
       WriteLn (Frac (12.543) : 1 : 5);  { 0.54300 }
       WriteLn (Int (12.543) : 1 : 5);  { 12.00000 }
       WriteLn (Round (12.543) : 1);  { 13 }
       WriteLn (Trunc (12.543) : 1);  { 12 }
     
       WriteLn (Frac (-12.543) : 1 : 5);  { -0.54300 }
       WriteLn (Int (-12.543) : 1 : 5);  { -12.00000 }
       WriteLn (Round (-12.543) : 1);  { -13 }
       WriteLn (Trunc (-12.543) : 1);  { -12 }
     end.

See also

Real Types, Real, Int, Frac, Trunc.

Node: RunError, Next: , Previous: Round, Up: Reference

RunError

(Under construction.)

Synopsis

     procedure RunError (ErrorCode: Integer);

Description

Conforming to

RunError is a Borland Pascal extension.

Example

See also

Node: Seek, Next: , Previous: RunError, Up: Reference

Seek

(Under construction.)

Synopsis

     procedure Seek (var F: typed_file; NewPosition: Integer);

Description

Conforming to

Seek is a UCSD Pascal extension.

Example

See also

Node: SeekEOF, Next: , Previous: Seek, Up: Reference

SeekEOF

(Under construction.)

Synopsis

     function SeekEOF ([var F: Text]): Boolean;

Description

Conforming to

SeekEOF is a Borland Pascal extension.

Example

See also

Node: SeekEOLn, Next: , Previous: SeekEOF, Up: Reference

SeekEOLn

(Under construction.)

Synopsis

     function SeekEOLn ([var F: Text]): Boolean;

Description

Conforming to

SeekEOLn is a Borland Pascal extension.

Example

See also

Node: SeekRead, Next: , Previous: SeekEOLn, Up: Reference

SeekRead

(Under construction.)

Synopsis

     procedure SeekRead (var F: typed_file; NewPosition: Integer);

Description

Conforming to

SeekRead is an ISO 10206 Extended Pascal extension.

Example

See also

Node: SeekUpdate, Next: , Previous: SeekRead, Up: Reference

SeekUpdate

(Under construction.)

Synopsis

     procedure SeekUpdate (var F: typed_file; NewPosition: Integer);

Description

Conforming to

SeekUpdate is an ISO 10206 Extended Pascal extension.

Example

See also

Node: SeekWrite, Next: , Previous: SeekUpdate, Up: Reference

SeekWrite

(Under construction.)

Synopsis

     procedure SeekWrite (var F: typed_file; NewPosition: Integer);

Description

Conforming to

SeekWrite is an ISO 10206 Extended Pascal extension.

Example

See also

Node: segment, Next: , Previous: SeekWrite, Up: Reference

segment

Not yet implemented.

Synopsis

Description

Segment specification.

Conforming to

segment is a UCSD Pascal extension.

Example

See also

Keywords.

Node: Self, Next: , Previous: segment, Up: Reference

Self

(Under construction.)

Synopsis

Description

Conforming to

Self is an Object Pascal and a Borland Pascal extension.

Example

See also

Node: set, Next: , Previous: Self, Up: Reference

set

Synopsis

In type definitions: 

     set of Type  { built-in type class }

Description

A set contains zero or more elements from an ordinal type, e.g. Char, a subrange of Char, or a subrange of an enumerated type or integers. Sets do not have any ordering (that is a set containing 'B' and 'A' is the same as a set containing 'A' and 'B'), nor can an element be included more than once. Sets simply store the information about which elements are included in the set.

Conforming to

set is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program SetDemo;
     
     type
       TCharSet = set of Char;
     
     var
       Ch: Char;
       MyCharSet: TCharSet;
     begin
       MyCharSet := ['P','N','L'];
       if 'A' in MyCharSet then
         WriteLn ('Wrong: A in set MyCharSet')
       else
         WriteLn ('Right: A is not in set MyCharSet');
       Include (MyCharSet, 'A');  { A, L, N, P }
       Exclude (MyCharSet, 'N');  { A, L, P }
       MyCharSet := MyCharSet + ['B','C'];  { A, B, C, L, P }
       MyCharSet := MyCharSet - ['C','D'];  { A, B, L, P }
       WriteLn ('set MyCharSet contains:');
       for Ch in MyCharSet do
         WriteLn (Ch);
     end.

Set also Set Operations or examples of some of the many set operations.

See also

Keywords, Set Operations, in, Exclude, Include.

Node: SetFileTime, Next: , Previous: set, Up: Reference

SetFileTime

     procedure SetFileTime (var f: any_file;
                            AccessTime, ModificationTime: UnixTimeType);

Synopsis

Description

Conforming to

SetFileTime is a GNU Pascal extension.

Example

See also

Node: SetLength, Next: , Previous: SetFileTime, Up: Reference

SetLength

Synopsis

     procedure SetLength (var S: String; NewLength: Integer);

Description

SetLength explicitly assigns a new length NewLength to the string parameter S. The contents of the string is not changed; if the operation increases the length of the string, the characters appended at the end are undefined.

Conforming to

SetLength is a Borland Delphi 2.0 extension.

Example

     program SetLengthDemo;
     
     var
       S: String (26);
     
     begin
       S := 'Hello, world!';
       SetLength (S, Length ('Hello'));
       WriteLn (S);                                           { 'Hello' }
     
       SetLength (S, 26);
       WriteLn (S);                     { 'Hello, world!(%$xy"!#&~+(/]' }
                                 { undefined characters ^^^^^^^^^^^^^^  }
     
       SetLength (S, 42);       { The overflow is *not* (yet) detected. }
       WriteLn (S);        { This might cause a runtime error or crash. }
     end.

See also

Length, String.

Node: SetType, Next: , Previous: SetLength, Up: Reference

SetType

Synopsis

     procedure SetType (var SomeObject; VMT: PObjectType);

Description

The procedure SetType explicitly assigns a value to the implicit VMT field of an object. This is normally done implicitly when a constructor is called.

You can use this to write a polymorphic I/O routine which reads an object from a file. In this case, you cannot reasonably use New to allocate the storage, but you GetMem it and initialize the object manually using SetType before calling the constructor explicitly.

The only values you should assign to an object via SetType are actual VMT pointers that were obtained via TypeOf. In particular, declaring a record like the one shown in the description of PObjectType and assigning a pointer to it to an object via SetType will usually not work because the virtual method pointers are missing.

Since SetType is a dangerous feature, it yields a warning unless {$X+} is given.

Conforming to

SetType is a GNU Pascal extension.

Example

     program SetTypeDemo;
     
     type
       BasePtr = ^BaseObj;
     
       BaseObj = object
         constructor Load;
       end;
     
       ChildObj = object (BaseObj)
         constructor Load;
       end;
     
     constructor BaseObj.Load;
     begin
     end;
     
     constructor ChildObj.Load;
     begin
     end;
     
     {$X+}
     
     { This is somewhat fragmentary code. }
     function GetObject (var InputFile: File) = Result: BasePtr;
     const
       VMTTable: array [1 .. 2] of PObjectType =
         (TypeOf (BaseObj), TypeOf (ChildObj));
     var
       Size: Cardinal;
       TypeID: Integer;
       VMT: PObjectType;
     begin
       { Read the size of the object from some file and store it in `Size'. }
       BlockRead (InputFile, Size, SizeOf (Size));
     
       { Allocate memory for the object. }
       GetMem (Result, Size);
     
       { Read some ID from some file. }
       BlockRead (InputFile, TypeID, SizeOf (TypeID));
     
       { Look up the `VMT' from some table. }
       { Range checking wouldn't be a bad idea here ... }
       VMT := VMTTable[TypeID];
     
       SetType (Result^, VMT);
     
       { Now the object is ready, and the constructor can be called. }
       { Look up the correct constructor from some table and call it. }
     end;
     
     begin
     end.

See also

PObjectType, TypeOf, OOP.

Node: shl, Next: , Previous: SetType, Up: Reference

shl

Synopsis

     operator shl (operand1, operand2: integer_type) = Result: integer_type;
or 
     procedure shl (var operand1: integer_type; operand2: integer_type);

Description

In GNU Pascal, shl has two built-in meanings:

  1. Bitwise shift left of an integer-type expression by another integer value. The result is of the type of the first operand.
  2. Use as a "procedure": operand1 is shifted left by operand2; the result is stored in operand1.

Conforming to

shl is a Borland Pascal extension.

Use of shl as a "procedure" is a GNU Pascal extension.

Example

     program ShlDemo;
     var
       a: Integer;
     begin
       a := 1 shl 7;  { yields 128 = 2 pow 7 }
       shl (a, 4)  { same as `a := a shl 4' }
     end.

See also

Keywords, shr, Operators.

Node: ShortBool, Next: , Previous: shl, Up: Reference

ShortBool

Synopsis

     type
       ShortBool = Boolean attribute (Size = BitSizeOf (ShortInt));

Description

The intrinsic ShortBool represents boolean values, but occupies the same memory space as a ShortInt. It is used when you need to define a parameter or record that conforms to some external library or system specification.

Conforming to

ShortBool is a GNU Pascal extension.

Example

     program ShortBoolDemo;
     var
       a: ShortBool;
     begin
       ShortInt (a) := 1;
       if a then WriteLn ('Ord (True) = 1')
     end.

See also

Boolean (Intrinsic), Boolean, True, False, CBoolean, ByteBool, MedBool, WordBool, LongBool, LongestBool.

Node: ShortCard, Next: , Previous: ShortBool, Up: Reference

ShortCard

Synopsis

     type
       ShortCard = Cardinal attribute (Size = BitSizeOf (ShortInt));

Description

ShortCard is an unsigned integer type which is not larger than Cardinal. On most platforms it is 16 bits wide and thus has a range of 0..65535.

ShortCard in GNU Pascal is compatible to short unsigned int in GNU C.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

ShortCard is a GNU Pascal extension.

Example

     program ShortCardDemo;
     var
       a: ShortCard;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: ShortInt, Next: , Previous: ShortCard, Up: Reference

ShortInt

Synopsis

     type
       ShortInt  { built-in type }

Description

ShortInt is a signed integer type which is not larger than Integer. On most platforms it is 16 bits wide and thus has a range of -32768..32767.

ShortInt in GNU Pascal is compatible to short int in GNU C.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

ShortInt is a Borland Pascal extension. In Borland Pascal, ShortInt is an 8-bit signed integer type (ByteInt in GNU Pascal).

Example

     program ShortIntDemo;
     var
       a: ShortInt;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: ShortReal, Next: , Previous: ShortInt, Up: Reference

ShortReal

(Under construction.)

Synopsis

     type
       ShortReal  { built-in type }

Description

Conforming to

ShortReal is a GNU Pascal extension.

Example

     program ShortRealDemo;
     var
       a: ShortReal;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Node: ShortWord, Next: , Previous: ShortReal, Up: Reference

ShortWord

Synopsis

     type
       ShortWord = ShortCard;

Description

ShortWord is an unsigned integer type which is not larger than Word. On most platforms it is 16 bits wide and thus has a range of 0..65535. It is the same as ShortCard.

ShortWord in GNU Pascal is compatible to short unsigned int in GNU C.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

ShortWord is a GNU Pascal extension.

ShortWord in GNU Pascal essentially corresponds to Word in Borland Pascal and Delphi where it is a 16-bit unsigned integer type.

Example

     program ShortWordDemo;
     var
       a: ShortWord;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: shr, Next: , Previous: ShortWord, Up: Reference

shr

Synopsis

     operator shr (operand1, operand2: integer_type) = Result: integer_type;
or 
     procedure shr (var operand1: integer_type; operand2: integer_type);

Description

In GNU Pascal, shr has two built-in meanings:

  1. Bitwise shift right of an integer-type expression by another integer value. The result is of the type of the first operand.
  2. Use as a "procedure": operand1 is shifted right by operand2; the result is stored in operand1.

Conforming to

shr is a Borland Pascal extension.

Unlike the Borland compilers, GNU Pascal cares about the signedness of the first operand: If a signed integer with a negative value is shifted right, "one" bits are filled in from the left.

Use of shr as a "procedure" is a GNU Pascal extension.

Example

     program ShrDemo;
     var
       a: Integer;
     begin
       a := 1024 shr 4;  { yields 64 }
       a := -127 shr 4;  { yields -8 }
       shr (a, 2)  { same as `a := a shr 2' }
     end.

See also

Keywords, shl, Operators.

Node: Sin, Next: , Previous: shr, Up: Reference

Sin

Synopsis

     function Sin (x: Real): Real;
or 
     function Sin (z: Complex): Complex;

Description

Sin returns the sine of the argument. The result is in the range -1 <= Sin (x) <= 1 for real arguments.

Conforming to

The function Sin is defined in ISO 7185 Pascal; its application to complex values is defined in ISO 10206 Extended Pascal.

Example

     program SinDemo;
     begin
       { yields 0.5 since Sin (Pi / 6) = 0.5 }
       WriteLn (Sin (Pi / 6) : 0 : 5)
     end.

See also

ArcTan, Cos, Ln, Arg.

Node: Single, Next: , Previous: Sin, Up: Reference

Single

(Under construction.)

Synopsis

     type
       Single = ShortReal;

Description

Conforming to

Single is a Borland Pascal extension.

Example

See also

Node: SizeOf, Next: , Previous: Single, Up: Reference

SizeOf

Synopsis

     function SizeOf (var x): SizeType;

Description

Returns the size of a type or variable in bytes.

SizeOf can be applied to expressions and type names. If the argument is a polymorphic object, the size of its actual type is returned.

Conforming to

SizeOf is a UCSD Pascal extension.

Example

     program SizeOfDemo;
     var
       a: Integer;
       b: array [1 .. 8] of Char;
     begin
       WriteLn (SizeOf (a));        { Size of an `Integer'; often 4 bytes. }
       WriteLn (SizeOf (Integer));  { The same. }
       WriteLn (SizeOf (b))         { Size of eight `Char's; usually 8 bytes. }
     end.

See also

BitSizeOf, AlignOf, TypeOf.

Node: SizeType, Next: , Previous: SizeOf, Up: Reference

SizeType

Synopsis

     type
       SizeType  { built-in type }

Description

SizeType is an integer type (usually unsigned) to represent the size of objects in memory.

Conforming to

SizeType is a GNU Pascal extension.

Example

     program SizeTypeDemo;
     var
       a: array [1 .. 10] of Integer;
       Size: SizeType;
     begin
       Size := SizeOf (a);
       WriteLn (Size)
     end.

See also

Node: SmallInt, Next: , Previous: SizeType, Up: Reference

SmallInt

Synopsis

     type
       SmallInt = ShortInt;

Description

SmallInt is a signed integer type which is not larger than Integer. On most platforms it is 16 bits wide and thus has a range of -32768..32767. It is the same as ShortInt (see ShortInt).

There are lots of other integer types in GPC, see Integer Types.

Conforming to

SmallInt is a Borland Delphi 2.0 extension.

Example

     program SmallIntDemo;
     var
       a: SmallInt;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

ShortInt, Integer Types, Subrange Types.

Node: Sqr, Next: , Previous: SmallInt, Up: Reference

Sqr

Synopsis

     function Sqr (i: integer_type): integer_type;
or 
     function Sqr (x: real_type): real_type;
or 
     function Sqr (z: complex_type): complex_type;

Description

Returns the square of the argument: 

     function Sqr (x: some_type): some_type;
     begin
       Sqr := x * x  { or: x pow 2 }
     end;

Conforming to

The function Sqr is defined in ISO 7185 Pascal; its application to complex values is defined in ISO 10206 Extended Pascal.

Example

     program SqrDemo;
     
     var
       i: Complex;
     
     begin
       i := Cmplx (0, 1);
       WriteLn (Re (Sqr (i)) : 0 : 3)  { yields -1.000 }
     end.

See also

pow, SqRt, Abs, Operators.

Node: SqRt, Next: , Previous: Sqr, Up: Reference

SqRt

Synopsis

     function SqRt (x: real_type): real_type;
or 
     function SqRt (z: complex_type): complex_type;

Description

Returns the positive square root of the argument.

For real arguments, it is an error if the argument is negative.

For complex arguments, SqRt returns the principal value of the root of the argument, i.e. the root with positive real part, or, if the real part is zero, that one with positive imaginary part.

Conforming to

The function SqRt is defined in ISO 7185 Pascal; its application to complex values is defined in ISO 10206 Extended Pascal.

Example

     program SqRtDemo;
     
     var
       m1: Complex;
     
     begin
       m1 := Cmplx (-1, 0);  { -1 }
       WriteLn (Re (SqRt (m1)) : 6 : 3, Im (SqRt (m1)) : 6 : 3);
         { yields 1.000 -1.000, i.e. the imaginary unit, i }
     end.

See also

pow, Sqr, Operators.

Node: StandardError, Next: , Previous: SqRt, Up: Reference

StandardError

(Under construction.)

Synopsis

Description

Conforming to

StandardError is a GNU Pascal extension.

Example

See also

Node: StandardInput, Next: , Previous: StandardError, Up: Reference

StandardInput

(Under construction.)

Synopsis

Description

Conforming to

StandardInput is an ISO 10206 Extended Pascal extension.

Example

See also

Node: StandardOutput, Next: , Previous: StandardInput, Up: Reference

StandardOutput

(Under construction.)

Synopsis

Description

Conforming to

StandardOutput is an ISO 10206 Extended Pascal extension.

Example

See also

Node: StdErr, Next: , Previous: StandardOutput, Up: Reference

StdErr

Synopsis

     var
       StdErr: Text;

Description

The StdErr variable is connected to the standard error file handle. To report errors, you should prefer WriteLn (StdErr, 'everything wrong') over WriteLn ('everything wrong').

Conforming to

StdErr is a GNU Pascal extension.

Example

     program StdErrDemo;
     var
       Denominator: Integer;
     begin
       ReadLn (Denominator);
       if Denominator = 0 then
         WriteLn (StdErr, ParamStr (0), ': division by zero')
       else
         WriteLn ('1 / ', Denominator, ' = ', 1 / Denominator)
     end.

See also

StandardError, Output, Input.

Node: Str, Next: , Previous: StdErr, Up: Reference

Str

(Under construction.)

Synopsis

     procedure Str (x: integer_or_real; var Dest: String);
or 
     procedure Str (x: integer_or_real : field_width; var Dest: String);
or 
     procedure Str (x: Real : field_width : precision; var Dest: String);
or 
     procedure Str (repeated_constructs_as_described_above; var Dest: String);

Description

Conforming to

Str is a UCSD Pascal extension, generalized by Borland Pascal. The possibility to handle more than one variable with one call to Str is a GNU Pascal extension.

ISO 10206 Extended Pascal defines WriteStr instead of Str.

Example

See also

WriteStr.

Node: String, Next: , Previous: Str, Up: Reference

String

(Under construction.)

Synopsis

Description

Conforming to

String is an Extended Pascal and a UCSD Pascal extension.

Example

See also

Node: String2CString, Next: , Previous: String, Up: Reference

String2CString

(Under construction.)

Synopsis

     function String2CString (const S: String): CString;

Description

Conforming to

String2CString is a GNU Pascal extension.

Example

See also

Node: SubStr, Next: , Previous: String2CString, Up: Reference

SubStr

Synopsis

     function SubStr (S: String; FirstChar: Integer): String;
or 
     function SubStr (S: String; FirstChar, Count: Integer): String;

Description

SubStr returns a sub-string of S starting with the character at position FirstChar. If Count is given, such many characters will be copied into the sub-string. If Count is omitted, the sub-string will range to the end of S.

If Count is too large for the sub-string to fit in S or if FirstChar exceeds the length of S, SubStr triggers a runtime error. (For a function returning the empty string instead, see Copy.)

Conforming to

SubStr is an ISO 10206 Extended Pascal extension.

Example

     program SubStrDemo;
     var
       S: String (42);
     begin
       S := 'Hello';
       WriteLn (SubStr (S, 2, 3));   { yields `ell' }
       WriteLn (SubStr (S, 3));      { yields `llo' }
       WriteLn (SubStr (S, 4, 7));   { yields a runtime error }
       WriteLn (SubStr (S, 42));     { yields a runtime error }
     end.

See also

Copy, String Slice Access.

Node: Succ, Next: , Previous: SubStr, Up: Reference

Succ

Synopsis

     function Succ (i: ordinal_type): ordinal_type;
or 
     function Succ (i: ordinal_type; j: Integer): ordinal_type;

or, with extended syntax (--extended-syntax or {$X+}), 

     function Succ (p: Pointer_type): Pointer_type;
or 
     function Succ (p: Pointer_type; j: Integer): Pointer_type;

Description

Returns the successor of the ordinal_type value i, or, if the second argument j is given, its jth successor. For integer values i, this is i + 1 (or i + j). (No, Succ does not work faster than plain addition. Both are optimized the same way, often to a single machine instruction.)

If extended syntax is on, the argument may also be a pointer value. In this case, the address is incremented by the size of the variable pointed to, or, if j is given, by j times the size of the variable pointed to. If p points to an element of an array, the returned pointer will point to the (jth) next element of the array.

Conforming to

The Succ function is defined in ISO 7185 Pascal. The optional second parameter is defined in ISO 10206 Extended Pascal. Application of Succ to pointers is defined in Borland Pascal. The combination of the second argument with application to pointers is a GNU Pascal extension.

Example

     program SuccDemo;
     
     type
       Metasyntactical = (foo, bar, baz);
     
     var
       m: Metasyntactical;
       c: Char;
       a: array [1 .. 7] of Integer;
       p: ^Integer;
     
     begin
       m := Succ (foo);     { bar }
       c := Succ ('A', 4);  { 'E' }
       a[1] := 42;
       a[2] := Succ (a[1]);     { 43 }
       a[5] := Succ (a[2], 7);  { 50 }
       {$X+}
       p := @a[1];
       p := Succ (p);     { points to `a[2]' now }
       p := Succ (p, 3);  { points to `a[5]' now }
     end.

See also

Pred, Inc, Pointer Arithmetics.

Node: Text, Next: , Previous: Succ, Up: Reference

Text

(Under construction.)

Synopsis

     type
       Text  { built-in type }

Description

Conforming to

Text is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program TextDemo;
     var
       t: Text;
     begin
       Rewrite (t, 'hello.txt');
       WriteLn (t, 'Hello, world!')
     end.

See also

file, AnyFile.

Node: then, Next: , Previous: Text, Up: Reference

then

(Under construction.)

Synopsis

Description

Part of an if statement or part of the and then operator.

Conforming to

then is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program ThenDemo;
     var
       i: Integer;
     begin
       Write ('Enter a number: ');
       ReadLn (i);
       if i > 42 then
         WriteLn ('The number is greater than 42')
     end.

See also

Keywords.

Node: Time, Next: , Previous: then, Up: Reference

Time

Synopsis

     function Time (T: TimeStamp): packed array [1 .. Time_Length] of Char;

Description

Date takes a TimeStamp parameter and returns the time as a string (in the form of a packed array of Char). Time_length is an implementation defined invisible constant.

Conforming to

Time is an ISO 10206 Extended Pascal extension.

Example

Set TimeStamp.

See also

TimeStamp, GetTimeStamp, Date, Date And Time Routines.

Node: TimeStamp, Next: , Previous: Time, Up: Reference

TimeStamp

Synopsis

     type
       TimeStamp = packed record
         DateValid,
         TimeValid  : Boolean;
         Year       : Integer;
         Month      : 1 .. 12;
         Day        : 1 .. 31;
         DayOfWeek  : 0 .. 6;   { 0 means Sunday }
         Hour       : 0 .. 23;
         Minute     : 0 .. 59;
         Second     : 0 .. 61;  { to allow for leap seconds }
         MicroSecond: 0 .. 999999;
         TimeZone   : Integer;  { in seconds east of UTC }
         DST        : Boolean;
         TZName1,
         TZName2    : String (32);
       end;

The fields DateValid, TimeValid, Year, Month, Day, Hour, Minute, Second are required by Extended Pascal, the other ones are extensions.

Description

The TimeStamp record holds all the information about a particular time. You can get the current time with GetTimeStamp and you can get the date or time in a printable form using the Date and Time functions.

Conforming to

TimeStamp is an ISO 10206 Extended Pascal extension.

Example

     program TimeStampDemo;
     
     var
       t: TimeStamp;
     
     begin
       GetTimeStamp (t);
       WriteLn ('DateValid: ', t.DateValid);
       WriteLn ('TimeValid: ', t.TimeValid);
       WriteLn ('Year: ', t.Year);
       WriteLn ('Month: ', t.Month);
       WriteLn ('Day: ', t.Day);
       WriteLn ('DayOfWeek (0..6, 0=Sunday): ', t.DayOfWeek);
       WriteLn ('Hour (0..23): ', t.Hour);
       WriteLn ('Minute (0..59): ', t.Minute);
       WriteLn ('Second (0..61): ', t.Second);
       WriteLn ('MicroSecond (0..999999): ', t.MicroSecond);
       WriteLn ('TimeZone (in seconds east of UTC): ', t.TimeZone);
       WriteLn ('DST: ', t.DST);
       WriteLn ('TZName1: ', t.TZName1);
       WriteLn ('TZName2: ', t.TZName2);
       WriteLn;
       WriteLn ('Date is: ', Date (t));
       WriteLn ('Time is: ', Time (t));
     end.

See also

GetTimeStamp, Date, Time, Date And Time Routines.

Node: to, Next: , Previous: TimeStamp, Up: Reference

to

(Under construction.)

Synopsis

Description

Part of a for loop counting upwards or a to begin do or to end do module constructor or destructor.

Conforming to

to is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Keywords.

Node: to begin do, Next: , Previous: to, Up: Reference

to begin do

(Under construction.)

Synopsis

Description

Conforming to

to begin do is an ISO 10206 Extended Pascal extension.

Example

See also

Keywords.

Node: to end do, Next: , Previous: to begin do, Up: Reference

to end do

(Under construction.)

Synopsis

Description

Conforming to

to begin end is an ISO 10206 Extended Pascal extension.

Example

See also

Keywords.

Node: Trim, Next: , Previous: to end do, Up: Reference

Trim

(Under construction.)

Synopsis

     function Trim (S: String): String;

Description

Conforming to

Trim is an ISO 10206 Extended Pascal extension.

Example

See also

Node: True, Next: , Previous: Trim, Up: Reference

True

Synopsis

     type
       Boolean = (False, True);  { built-in type }

Description

True is one of the two Boolean values and is used to represent a condition which is always fullfilled. For example, the expression 1 = 1 always yields the value True. It is the opposite of False. True has the ordinal value 1.

Conforming to

True is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program TrueDemo;
     
     var
       a: Boolean;
     
     begin
       a := 1 = 1;  { yields True }
       WriteLn (Ord (True));  { 1 }
       WriteLn (a);  { True }
       if True then WriteLn ('This is executed.')
     end.

See also

Boolean (Intrinsic), False, Boolean.

Node: Trunc, Next: , Previous: True, Up: Reference

Trunc

Synopsis

     function Trunc (x: Real): Integer;

Description

Trunc returns the integer part of a floating point number as an integer. Use Int to get the integer part as a floating point number.

Conforming to

Trunc is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program TruncDemo;
     
     begin
       WriteLn (Frac (12.345) : 1 : 5);  { 0.34500 }
       WriteLn (Int (12.345) : 1 : 5);  { 12.00000 }
       WriteLn (Round (12.345) : 1);  { 12 }
       WriteLn (Trunc (12.345) : 1);  { 12 }
     
       WriteLn (Frac (-12.345) : 1 : 5);  { -0.34500 }
       WriteLn (Int (-12.345) : 1 : 5);  { -12.00000 }
       WriteLn (Round (-12.345) : 1);  { -12 }
       WriteLn (Trunc (-12.345) : 1);  { -12 }
     
       WriteLn (Frac (12.543) : 1 : 5);  { 0.54300 }
       WriteLn (Int (12.543) : 1 : 5);  { 12.00000 }
       WriteLn (Round (12.543) : 1);  { 13 }
       WriteLn (Trunc (12.543) : 1);  { 12 }
     
       WriteLn (Frac (-12.543) : 1 : 5);  { -0.54300 }
       WriteLn (Int (-12.543) : 1 : 5);  { -12.00000 }
       WriteLn (Round (-12.543) : 1);  { -13 }
       WriteLn (Trunc (-12.543) : 1);  { -12 }
     end.

See also

Real Types, Real, Int, Frac, Round.

Node: Truncate, Next: , Previous: Trunc, Up: Reference

Truncate

(Under construction.)

Synopsis

     procedure Truncate (var F: any_file);

Description

Conforming to

Truncate is a Borland Pascal extension.

Example

See also

Node: type, Next: , Previous: Truncate, Up: Reference

type

Synopsis

As a type declaration: 

     type
       type_indentifier = type_definition;
or with initialization: 
     type
       type_indentifier = type_definition value constant_expression;

Description

The reserved word type starts the declaration of a type identifier which is defined by type_definition. For further description see Type Declaration, Type Declaration, Type Definition, Data Types.

Conforming to

type is defined in ISO 7185 Pascal and supported by all known Pascal variants. Initializers are an ISO 10206 Extended Pascal extension.

Example

     program TypeDemo;
     type
       { This side is the }    { That side is the }
       { type declaration }    { type definition  }
     
       { array type }
       ArrayType                  = array [0 .. 9] of Integer;
     
       { record type }
       RecordType                 = record
                                      Bar: Integer
                                    end;
     
       { subrange type }
       SubrangeType               = -123 .. 456;
     
       { enumeration type }
       EnumeratedType             = (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
     
       { set type }
       CharSetType                = set of Char;
     
       { object type }
       ObjectType                 = object
                                      constructor Init;
                                      procedure Method;
                                      destructor Done
                                    end;
     
       { pointer type to another type identifier }
       PArrayType                 = ^ArrayType;
     
       { an alias name for another type identifier }
       IntegerType                = Integer;
     
       { an integer which is initialized by 123 }
       InitializedInt             = Integer value 123;
     
       { a schema with discriminants x and y of type Integer }
       SchemaType (x, y: Integer) = array [x .. y] of Integer;
     
     { Dummy methods of the object type }
     constructor ObjectType.Init;
     begin
     end;
     
     procedure ObjectType.Method;
     begin
     end;
     
     destructor ObjectType.Done;
     begin
     end;
     
     begin
     end.

See also

Keywords, Type Declaration, Type Definition, Data Types, Variable Declaration, array, record, object, set, Pointer, value.

Node: type of, Next: , Previous: type, Up: Reference

type of

(Under construction.)

Synopsis

Description

Conforming to

Example

See also

Keywords.

Node: TypeOf, Next: , Previous: type of, Up: Reference

TypeOf

Synopsis

     function TypeOf (var x): PObjectType;

Description

Returns a pointer to the VMT of an object type or variable. This pointer can be used to identify the type of an object.

TypeOf can be applied to expressions of object type and to object type names. In the former case, the actual type of polymorphic objects is returned.

Conforming to

TypeOf is a Borland Pascal extension.

Example

     program TypeOfDemo;
     type
       FooPtr = ^Foo;
       BarPtr = ^Bar;
     
       Foo = object         { Has a VMT, though it doesn't }
         x: Integer;        { contain virtual methods.     }
         constructor Init;
       end;
     
       Bar = object (Foo)
         y: Integer;
       end;
     
     constructor Foo.Init;
     begin
     end;
     
     var
       MyFoo: FooPtr;
     
     begin
       MyFoo := New (BarPtr, Init);
       if TypeOf (MyFoo^) = TypeOf (Bar) then  { True }
         WriteLn ('OK')
     end.

See also

BitSizeOf, AlignOf, PObjectType, SetType, SizeOf, OOP.

Node: Unbind, Next: , Previous: TypeOf, Up: Reference

Unbind

(Under construction.)

Synopsis

     procedure Unbind (var F: any_file);

Description

Conforming to

Unbind is an ISO 10206 Extended Pascal extension.

Example

See also

Bind, Binding, BindingType, bindable.

Node: unit, Next: , Previous: Unbind, Up: Reference

unit

(Under construction.)

Synopsis

Description

UCSD and BP style unit declaration.

Conforming to

unit is a UCSD Pascal extension.

Example

See also

Keywords.

Node: Unpack, Next: , Previous: unit, Up: Reference

Unpack

(Under construction.)

Synopsis

     procedure Unpack (Source: packed_array;
                       var Dest: unpacked_array;
                       FirstElement: index_type);

Description

Conforming to

Unpack is defined in ISO 7185 Pascal and supported by all known Pascal variants except UCSD/Borland Pascal and its variants.

Example

See also

Node: until, Next: , Previous: Unpack, Up: Reference

until

(Under construction.)

Synopsis

Description

until is part of the repeat ... until loop statement.

Conforming to

until is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Keywords, repeat, while, for.

Node: UpCase, Next: , Previous: until, Up: Reference

UpCase

(Under construction.)

Synopsis

     function UpCase (Ch: Char): Char;

Description

Conforming to

UpCase is a Borland Pascal extension.

Example

See also

Node: Update, Next: , Previous: UpCase, Up: Reference

Update

(Under construction.)

Synopsis

     procedure Update (var F: any_file);

Description

Conforming to

Update is an ISO 10206 Extended Pascal extension.

Example

See also

Node: uses, Next: , Previous: Update, Up: Reference

uses

Synopsis

In a program: 

     program @@fragment foo;
     
     uses
       bar1,
       bar2 in 'baz.pas',
       bar3;
     
     [...]

In a unit: 

     unit @@fragment Bar3;
     
     interface
     
     uses
       bar1,
       bar2 in 'baz.pas';
     
     [...]
     
     implementation
     
     uses
       bar3,
       bar4 in 'qux.pas';
     
     [...]

Description

The reserved word uses in the import part of a program or unit makes the program or unit import an interface.

The keyword in tells GPC to look for the unit in the specified file; otherwise the file name is derived from the name of the interface, coverted to lower-case, by adding first .p, then .pas.

There must be at most one import part in a program.

In a unit, there can be one import part in the interface part and one in the implementation part.

The imported interface needn't be a UCSD/Borland Pascal unit, it may be an interface exported by an Extended Pascal module as well.

Conforming to

ISO Pascal does not define uses and units at all. UCSD and Borland Pascal do, but without the in extension. Delphi supports uses like described above.

Example

See also

Keywords, unit, module, import.

Node: Val, Next: , Previous: uses, Up: Reference

Val

(Under construction.)

Synopsis

     procedure Val (const Source: String; var x: integer_or_real;
                    var ErrorPosition: Integer);

Description

Val converts the integer or real number that is represented by the characters in the string Source and places it into x.

The Source string can have a base prefix ($ for hexadecimal or Base#). The optional ErrorCode will be set to the position of the first invalid character, or to a 0 if the entire string represents a valid number. In case an invalid character occurrs in Source, x will be undefined.

Conforming to

Val is a Borland Pascal extension.

Example

     program ValDemo;
     var
       x, ec: Integer;
       l: LongInt;
       r: Real;
     begin
       Val ('123', x, ec);                { x :=            123; ec := 0; }
       Val ('-123', x, ec);               { x :=           -123; ec := 0; }
       Val ('123.456', r, ec);            { r :=        123.456; ec := 0; }
       Val ('$ffff', x, ec);              { x :=          65535; ec := 0; }
       Val ('$F000', x, ec);              { x :=          61440; ec := 0; }
       Val ('-$ffff', x, ec);             { x :=         -65535; ec := 0; }
       Val ('12#100', x, ec);             { x :=            144; ec := 0; }
       Val ('-2#11111111', x, ec);        { x :=           -255; ec := 0; }
       { here we have the invalid character 'X' for base 16 }
       Val ('$fffeX', x, ec);             { x :=    <undefined>; ec := 6; }
       Val ('12#100invalid', x, ec);      { x :=    <undefined>; ec := 7; }
       Val ('36#Jerusalem', l, ec);       { l := 54758821170910; ec := 0; }
     end.

See also

ReadLn, ReadStr, WriteLn, WriteStr, Str.

Node: value, Next: , Previous: Val, Up: Reference

value

Synopsis

Description

The reserved word value is part of a type or var declaration. It can be replaced by := or =.

Conforming to

value is an ISO 10206 Extended Pascal extension. := in this context is a VAX Pascal extension, and = is a Borland Delphi extension.

Example

See also

Keywords, var, type, Variable Declaration, Type Declaration.

Node: var, Next: , Previous: value, Up: Reference

var

Synopsis

As part of a variable declaration part or in a statement block: 

     var variable_identifier: type_identifier;
or 
     var variable_identifier: type_definition;
and with initializing value: 
     var variable_identifier: type_identifier value constant_expression;
or 
     var variable_identifier: type_definition value constant_expression;

As part of a parameter list (passing by reference): 

     var var_parameter: type_identifier;
or without type declaration 
     var var_parameter;

or protected (i.e., the called routine can't modify the parameter): 

     protected var var_parameter: type_identifier;
or without type declaration 
     protected var var_parameter;

Description

In a declaration part: The reserved word var declares a variable_identifier whose type is of type_identifier or which is defined by type_definition. For further description see Variable Declaration, Type Declaration, Type Definition, Data Types.

In a parameter list: see Subroutine Parameter List Declaration.

Conforming to

var is defined in ISO 7185 Pascal and supported by all known Pascal variants. Untyped var parameters in parameter lists are a UCSD Pascal extension. The ability to do var declarations in a statement block is a GNU Pascal extension.

Example

     program VarDemo;
     
     type
       FooType = Integer;
     
     var
       Bar: FooType;
       ArrayFoo: array [0 .. 9] of Integer;   { array var definition }
       FecordFoo: record                      { record var definition }
                    Bar: Integer
                  end;
       CharsetFoo: set of Char;               { set var }
       SubrangeFoo: -123 .. 456;              { subrange var }
       EnumeratedFoo: (Mon, Tue, Wed, Thu, Fri, Sat, Sun);  {enumerated var }
       PointerBar: ^FooType;                  { pointer var }
     
     procedure ReadFoo (var Foo: FooType);
     begin
       ReadLn (Foo)
     end;
     
     begin
       var Bar: Integer;  { GNU Pascal extension }
       Bar := 42
     end.

See also

Keywords, type, array, record, set, Subrange Types, Pointer, protected.

Node: view, Next: , Previous: var, Up: Reference

view

Not yet implemented.

Synopsis

Description

Object class view.

Conforming to

view is an Object Pascal extension.

Example

See also

Keywords.

Node: virtual, Next: , Previous: view, Up: Reference

virtual

(Under construction.)

Synopsis

Description

Virtual object method declaration.

Conforming to

virtual is an Object Pascal and a Borland Pascal extension.

Example

See also

Keywords.

Node: Void, Next: , Previous: virtual, Up: Reference

Void

(Under construction.)

Synopsis

     type
       Void  { built-in type }

Description

Conforming to

Void is a GNU Pascal extension.

Example

     program VoidDemo;
     
     procedure p (var x: Void);
     begin
     end;
     
     var
       i: Integer;
       s: String (42);
     
     begin
       p (i);
       p (s)
     end.

See also

Node: while, Next: , Previous: Void, Up: Reference

while

Synopsis

     while boolean_expression do
       statement

Description

The while statement declares a loop. For further description see while Statement.

Conforming to

while is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

     program WhileDemo;
     var
       Foo, Bar: Integer;
     begin
       WriteLn ('Enter an descending series of integer numbers.');
       WriteLn ('Terminate by breaking this rule.');
       WriteLn ('Enter start number: ');
       Bar := MaxInt;
       ReadLn (Foo);
       while Foo < Bar do
         begin
           Bar := Foo;
           ReadLn (Foo)
         end;
       WriteLn ('The last number of your series was: ', Bar)
     end.

See also

Keywords, repeat Statement, for Statement.

Node: with, Next: , Previous: while, Up: Reference

with

(Under construction.)

Synopsis

Description

Automatic record or object field access.

Conforming to

with is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

...

{ Note bar is shadowed by foo.bar } ...

See also

Keywords.

Node: Word, Next: , Previous: with, Up: Reference

Word

Synopsis

     type
       Word = Cardinal;

Description

Word is the "natural" unsigned integer type in GNU Pascal. On most platforms it is 32 bits wide and thus has a range of 0..4294967295. It is the same as Cardinal, introduced for compatibility with other Pascal compilers.

Word in GNU Pascal is compatible to unsigned int in GNU C.

There are lots of other integer types in GPC, see Integer Types.

Conforming to

ISO Pascal does not define Cardinal. (However see Subrange Types.)

The Word type appears in Borland Pascal and Delphi, too, where it is a 16-bit unsigned integer type.

Example

     program WordDemo;
     var
       a: Word;
     begin
       a := 42;
       WriteLn (a)
     end.

See also

Integer Types, Subrange Types.

Node: WordBool, Next: , Previous: Word, Up: Reference

WordBool

Synopsis

     type
       WordBool = Boolean attribute (Size = BitSizeOf (Word));

Description

The intrinsic WordBool represents boolean values, but occupies the same memory space as a Word. It is used when you need to define a parameter or record that conforms to some external library or system specification.

Conforming to

WordBool is a Borland Pascal extension.

Example

     program WordBoolDemo;
     var
       a: WordBool;
     begin
       Word (a) := 1;
       if a then WriteLn ('Ord (True) = 1')
     end.

See also

Boolean (Intrinsic), Boolean, True, False, CBoolean, ByteBool, ShortBool, MedBool, LongBool, LongestBool.

Node: Write, Next: , Previous: WordBool, Up: Reference

Write

(Under construction.)

Synopsis

     procedure Write (var F: typed_file; variable);
or 
     procedure Write (var F: Text; values_and_format_specifications);
or 
     procedure Write (values_and_format_specifications);

Description

Conforming to

Write is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Node: WriteLn, Next: , Previous: Write, Up: Reference

WriteLn

(Under construction.)

Synopsis

     procedure WriteLn (var F: Text; values_and_format_specifications);
or 
     procedure WriteLn (values_and_format_specifications);

Description

Conforming to

WriteLn is defined in ISO 7185 Pascal and supported by all known Pascal variants.

Example

See also

Node: WriteStr, Next: , Previous: WriteLn, Up: Reference

WriteStr

(Under construction.)

Synopsis

     procedure WriteStr (var Dest: String; values_and_format_specifications);

Description

Conforming to

WriteStr is an ISO 10206 Extended Pascal extension.

Example

See also

Node: xor, Previous: WriteStr, Up: Reference

xor

Synopsis

     operator xor (operand1, operand2: Boolean) = Result: Boolean;
or 
     operator xor (operand1, operand2: integer_type) = Result: integer_type;
or 
     procedure xor (var operand1: integer_type; operand2: integer_type);

Description

In GNU Pascal, xor has three built-in meanings:

  1. Logical "exclusive or" between two Boolean-type expressions. The result of the operation is of Boolean type. (Logical foo xor bar in fact has the same effect as foo <> bar.)
  2. Bitwise "exclusive or" between two integer-type expressions. The result is of the common integer type of both expressions.
  3. Use as a "procedure": operand1 is "xor"ed bitwise with operand2; the result is stored in operand1.

Conforming to

ISO Pascal does not define the xor operator; Borland Pascal and Delphi do.

Use of xor as a "procedure" is a GNU Pascal extension.

Example

     program XorDemo;
     var
       a, b, c: Integer;
     begin
       if (a = 0) xor (b = 0) then
         c := 1  { happens if either `a' or `b' is zero,    }
                 { but not if both are zero or both nonzero }
       else if (a xor b) = 0 then  { bitwise xor }
         c := 2  { happens if a = b }
       else
         xor (c, a)  { same as `c := c xor a' }
     end.

See also

Keywords, and, or, Operators.

Node: Keywords, Next: , Previous: Reference, Up: Top

9 Pascal keywords and operators supported by GNU Pascal.

This chapter lists all keywords understood by GNU Pascal. The keywords are taken from the following standards:

The table below lists all known keywords with short descriptions. The links point to the longer descriptions in the reference.

By default (using GPC extensions) all keywords are enabled. Only those are marked GPC in the table below that are valid only in the GPC extensions.

All keywords that are specific to some dialects (i.e., not marked "any") can also be used as identifiers (with a few exceptions, see below). Then, however, they generally cannot be used as keywords anymore. So you can compile code from dialects that use them as keywords and code that uses them as identifiers, i.e., you do not have to modify your correct ISO 7185 programs in order to compile them with GPC without any dialect option. Some words can even be used as keywords and identifiers in parallel, including forward (according to ISO 7185 Pascal), and near and far (according to Borland Pascal).

The exceptions are:

A dialect option turns off all keywords that do not belong to this dialect. Besides, any keyword can be enabled and disabled with the compiler options {$enable-keyword} and {$disable-keyword}.

absolute (BP, BD) (see absolute)
overloaded variable declaration
abstract (OP) (see abstract)
abstract object type or method declaration
all (all) (see all)
export (see export) extension (export foo = all)
and (any) (see and)
Boolean or bitwise and operator or part of the and then (see and then) operator
and_then (EP, OP) (see and_then)
short-circuit Boolean and (see and) operator
array (any) (see array)
array type declaration
as (OP, BD) (see as)
object type membership test and conversion
asm (BP, BD) (see asm)
GNU style inline assembler code
asmname (GPC) (see asmname)
DEPRECATED! linker name of routines and variables
attribute (GPC) (see attribute)
attributes of routines and variables
begin (any) (see begin)
begin of a code block, part of a to begin do (see to begin do) module constructor
bindable (EP, OP) (see bindable)
external bindability of files
c (GPC) (see c)
DEPRECATED! declaration of external routine
case (any) (see case)
multi-branch conditional statement or variant record (see record) type
c_language (GPC) (see c_language)
DEPRECATED! declaration of external routine
class (OP, BD) (see class)
OOE/Delphi style object class (not yet implemented)
const (any) (see const)
constant declaration or constant parameter declaration
constructor (OP, BP, BD) (see constructor)
object constructor
destructor (OP, BP, BD) (see destructor)
object destructor
div (any) (see div)
integer division operator
do (any) (see do)
part of a while (see while) or for (see for) loop, a with (see with) statement, or a to begin do (see to begin do) or to end do (see to end do) module constructor or destructor
downto (any) (see downto)
part of a for (see for) loop counting downwards
else (any) (see else)
alternative part of an if (see if) statement, default case (see case) branch or part of the or else (see or else) operator
end (any) (see end)
end of a code block, end of a case (see case) statement, end of a record (see record) or object declaration, part of a to end do (see to end do) module destructor
export (export) (see export)
module interface export
exports (BP, BD) (see exports)
library export (not yet implemented)
external (UCSD, BP, BD, MP) (see external)
declaration of external object
far (BP, BD) (see far)
BP directive (ignored)
file (any) (see file)
non-text file type declaration
finalization (BD) (see finalization)
unit finalization
for (any) (see for)
loop statement where the number of loops is known in advance
forward (any) (see forward)
declaration of a routine whose definition follows below
function (any) (see function)
function declaration
goto (any) (see goto)
statement to jump to a label (see label)
if (any) (see if)
conditional statement
implementation (all except CP) (see implementation)
module or unit implementation part
import (EP, OP) (see import)
module interface import
in (any) (see in)
set membership test or part of a for (see for) loop iterating through sets
inherited (OP, BP, BD, MP) (see inherited)
reference to methods of ancestor object types
initialization (BD) (see initialization)
unit initialization
interface (interface) (see interface)
module or unit interface part
interrupt (BP, BD) (see interrupt)
interrupt handler declaration (not yet implemented)
is (OP, BD) (see is)
object type membership test
label (any) (see label)
label declaration for a goto (see goto) statement
library (BP, BD) (see library)
library declaration (not yet implemented)
mod (any) (see mod)
integer remainder operator
module (module) (see module)
EP style or PXSC style module
name (name) (see name)
linker name
near (BP, BD) (see near)
BP directive (ignored)
nil (any) (see nil)
reserved value for unassigned pointers
not (any) (see not)
Boolean or bitwise negation operator
object (BP, BD, MP) (see object)
BP style object declaration
of (any) (see of)
part of an array (see array), set (see set) or typed file (see file) type declaration, a case (see case) statement, a variant record (see record) type or a type of (see type of) type inquiry
only (EP, OP) (see only)
import specification
operator (PXSC) (see operator)
operator declaration
or (any) (see or)
Boolean or bitwise or operator or part of the or else (see or else) operator
or_else (EP, OP) (see or_else)
short-circuit Boolean or (see or) operator
otherwise (EP, OP, MP) (see otherwise)
default case (see case) branch
packed (any) (see packed)
declaration of packed record (see record) or array (see array) types, also packed ordinal subranges
pow (EP, OP) (see pow)
exponentiation operator with integer exponent
private (private) (see private)
private object fields
procedure (any) (see procedure)
procedure declaration
program (any) (see program)
start of a Pascal program
property (OP, BD) (see property)
object properties (not yet implemented)
protected (protected) (see protected)
read-only formal parameters or module export and protected object fields
public (public) (see public)
public object fields
published (published) (see published)
published object fields
qualified (qualified) (see qualified)
import specification
record (any) (see record)
structured type declaration
repeat (any) (see repeat)
loop statement
resident (BP, BD) (see resident)
library export specification (not yet implemented)
restricted (EP, OP) (see restricted)
restricted type specification
segment (UCSD) (see segment)
segment specification (not yet implemented)
set (any) (see set)
set type declaration
shl (BP, BD, MP) (see shl)
bitwise left shift operator
shr (BP, BD, MP) (see shr)
bitwise right shift operator
then (any) (see then)
part of an if (see if) statement or part of the and then (see and then) operator
to (any) (see to)
part of a for (see for) loop counting upwards or a to begin do (see to begin do) or to end do (see to end do) module constructor or destructor
type (any) (see type)
type declaration or part of a type of (see type of) type inquiry
unit (UCSD, BP, BD, MP) (see unit)
UCSD and BP style unit declaration
until (any) (see until)
end of a repeat (see repeat) statement
uses (UCSD, BP, BD, MP) (see uses)
unit import
value (EP, OP) (see value)
variable/type initializer
var (any) (see var)
variable declaration or reference parameter declaration
view (OP) (see view)
object class view (not yet implemented)
virtual (OP, BP, BD, MP) (see virtual)
virtual object method declaration
while (any) (see while)
loop statement
with (any) (see with)
automatic record (see record) or object field access
xor (BP, BD, MP) (see xor)
Boolean or bitwise exclusive or operator

Node: Support, Next: , Previous: Keywords, Up: Top

10 Where to get support for GNU Pascal; how to report bugs.

Here you can find information on where to find the most up-to-date information about GPC, how you can get support (professional or voluntary), how to use GPC's Test Suite, and how to report new bugs you might encounter.

If you have problems with GNU Pascal, please read the relevant sections of the GPC Manual. The most current version of the manual is available at http://www.gnu-pascal.de/gpc/index.html for online browsing. You can also download the complete manual in HTML format (tar.bz2). The manual is also available in DVI format (compressed with bzip2) and PostScript format (compressed with bzip2) for printing.

If the manual doesn't help you, here is what we recommend you to do: FAQ Check the GPC FAQ

Node: Mailing List, Next: , Up: Support

10.1 The GPC Mailing List

There is a mailing list devoted to GNU Pascal. You can write to the mailing list, e.g. if you have problems installing GPC or if you found a problem with GPC (please see Reporting Bugs). You can also use it to discuss suggestions for improving GPC and, most welcome, to offer your help or contribute code, documentation or other work. Mails to the list should be in English.

To subscribe to the mailing list, send the command 

     subscribe gpc your@email.address
in the body of a mail to majordomo@gnu.de (not to gpc@gnu.de!). The subject is ignored. (Please replace your@email.address with your real email address.) For more info, send a line help to majordomo@gnu.de.

After subscribing, you can send a message to the mailing list by sending email to the list address gpc@gnu.de as if it were a person.

To leave the mailing list, send the command 

     unsubscribe gpc your@email.address
to majordomo@gnu.de.

You can reach a human moderator at gpc-owner@gnu.de.

There is a separate mailing list for discussions about GPC documentation, gpc-doc@gnu.de. To subscribe, send the command 

     subscribe gpc-doc your@email.address
to majordomo@gnu.de.

There is also a (low-traffic) announce list, gpc-announce@gnu.de that you can subscribe to stay up-to-date. To subscribe to the list, write an email with 

     subscribe gpc-announce your@email.address
in the body to majordomo@gnu.de. If you like to announce a contribution, a service or an event related to GPC, you are invited to post to this list rather than gpc@gnu.de, but please don't use the announce list for questions or discussions. Please note that all mail sent to the announce list is forwarded to the regular list, so you won't have to subscribe to both lists if you don't want to miss anything. For the same reason, please don't cross-post to both lists.

There is also a German speaking mailing list, gpc-de@gnu.de. To subscribe send the command 

     subscribe gpc-de your@email.address
in the body of a mail to majordomo@gnu.de (note the hints above).

Node: Mailing List Archives, Next: , Previous: Mailing List, Up: Support

10.2 The GPC Mailing List Archives

Perhaps your problem was already discussed on the list. There is a searchable archive of the mailing list on the WWW. It can be browsed or searched at 

     http://www.gnu-pascal.de/crystal/gpc/en/

The archive of the documentation list is at 

     http://www.gnu-pascal.de/crystal/gpc-doc/en/

The archive of the announce list is at 

     http://www.gnu-pascal.de/crystal/gpc-announce/en/

The archive of the German GPC list is at 

     http://www.gnu-pascal.de/crystal/gpc-de/de/

Node: Newsgroups, Next: , Previous: Mailing List Archives, Up: Support

10.3 Newsgroups relevant to GPC

To get support, you can also ask the Usenet newsgroups for help. There are several Pascal related newsgroups, but none is dedicated just to GNU Pascal, so use the one which is most appropriate for your problem. For general Pascal questions, we recommend the following one:

news://comp.lang.pascal.misc Pascal in general and ungrouped Pascals.

Pascal syntax related questions may be appropriate in:

news://comp.lang.pascal.ansi-iso Pascal according to ANSI and ISO standards.

The next newsgroup is a haven for beginners, answering questions that would apply to almost any Pascal. However, if you have a GPC-specific question don't post there - use the GPC mailing list. And when in doubt use the GPC mailing list.

news://comp.lang.pascal.borland Borland Pascal questions.

Don't forget to give back what you have obtained. None of us is getting money for answering your questions (unless you pay us by yourself). Please do your part by answering the questions of others instead.

Node: Professional Support, Next: , Previous: Newsgroups, Up: Support

10.4 Where to get individual support for GPC

GPC is free software and comes without any warranty.

If you want to get professional support, you can hire an individual or a company for providing such a service. G-N-U GmbH is doing large parts of the development of GNU Pascal. This company offers special support for GPC and can be contacted at info@g-n-u.de.

More generally, to find a company or an individual who offers support and other consulting services for free software, look into the GNU Service Directory.

Node: Compiler Crashes, Next: , Previous: Professional Support, Up: Support

10.5 If the compiler crashes ...

If the compiler crashes, you have discovered a bug. A reliable compiler never crashes. To help the maintainers fix this bug, it is important that you send us a problem report.

If you're on Unix, you can find out where the compiler crashed if you enable coredumps, then load the compiler (gpc1) plus the core file in the debugger (gdb /your_path_here/gpc1 core), then type backtrace to get a stacktrace. Include this stacktrace in your bug report.

Node: Reporting Bugs, Next: , Previous: Compiler Crashes, Up: Support

10.6 How to report GPC bugs

If you encounter a bug with GPC, please check whether it is one of the known bugs (see Known Bugs). If not, please report it to the GNU Pascal mailing list (see Mailing List). That way, they always reach the maintainers. Please note the following points.

If the problem is with the compiler itself, not an installation problem or something like this, please provide a test program to reproduce the problem, and note the following hints. You can also contribute test programs for features that are working in GPC to ensure they will not break in future releases.

The preferred form for test programs is the form that the automated GPC Test Suite understands. Please, if at all possible, send your test programs in this form which should be easy to do, so we won't have to waste our time to bring them into this form, and can concentrate on fixing the problem.

The following special features of the Test Suite may be helpful for constructing slightly unusual tests:

Node: Testing, Previous: Reporting Bugs, Up: Support

10.7 Running the GPC Test Suite

Note: If you have installed a GPC binary distribution, you usually don't have the Test Suite installed (you can download the GPC source distribution to get it, however), so this section does not apply to you. Still, you can find in the section Contributing Tests to the Test Suite how to report GPC bugs in the form of new test programs so we can fix them as fast as possible.

The files in the test directory and subdirectories are for testing GPC only and should not be of any other use.

Note: A few of the tests do not make sense on all systems. They are equipped with checks and will be skipped if they find the system not suitable. Skipped tests do not indicate a GPC bug, unless you have a reason to be sure that the particular test should make sense on your system.

Node: To Do, Next: , Previous: Support, Up: Top

11 The GNU Pascal To-Do List.

This is the To-Do list for the GNU Pascal Compiler.

The GNU Pascal development team is constantly working on making GNU Pascal more reliable and more comfortable. However, there are some known bugs which will take some time to be fixed (any help welcome!), and we do not want to hide them from you. You might also be interested to know what features are planned to be implemented in the future. This list is meant to keep track of the known bugs and wanted features of GPC.

If you want to report a new bug or suggest a new feature, the best way to do it is in the mailing list. This way, other GPC users can provide additional ideas, perhaps work-arounds for bugs, and the GPC maintainers can sooner start to think about how to solve the problem. The GPC mailing list is gpc@gnu.de. To subscribe, send the command subscribe gpc your@email.address in the body of a mail to majordomo@gnu.de (the subject is ignored). An archive of the mailing list can be found at http://www.gnu-pascal.de/crystal/gpc/en/.

The list changes regularly. The present version refers to the current GPC snapshot, 20040516.

This list is part of the GNU Pascal Manual, included in GPC distributions and snapshots. You can always browse the most current version of the list on GPC's WWW page. If you check the To-Do list regularly you can decide if and when to try a new snapshort.

Node: Known Bugs, Next: , Up: To Do

11.1 Known bugs in GPC

In this section, you can find information about GPC bugs that are known to the developers.

If you encounter a bug with GPC, please check whether it is one of the known bugs. If not, report it to the GNU Pascal mailing list. (But always report if you solve the problem! :-)

Solved problems are moved to "Fixed Bugs" (see Fixed Bugs), and implemented features to the "News" chapter (see News).

A message ID (like <42@foo.bar>) refers to a message in the GPC mailing list or a newsgroup where the topic was discussed (often a bug report). A note of the form (xy20001231) refers to an internal message of the GPC developers. A file name like (foo42.pas) refers to the according program in the GPC test suite included in the GPC source distribution.

Node: Planned Features, Next: , Previous: Known Bugs, Up: To Do

11.2 Features planned for GPC

In the following sections, you can find informations about features which have been suggested and/or discussed for inclusion into GPC, usually in the GPC mailing list. The division into the sections and the names of the sections may change when this seems useful. The entries within each section are in no particular order.

Some of the entries may be a bit difficult to read. Double question marks (??) within the entries mean that it's not yet clear how to do the thing. Triple question marks (???) mean that it's not clear whether to do it at all. ;-)

Node: Planned - Strings, Next: , Up: Planned Features

11.2.1 Planned features: Strings

Node: Planned - Records/arrays, Next: , Previous: Planned - Strings, Up: Planned Features

11.2.2 Planned features: Records/arrays

Node: Planned - Files, Next: , Previous: Planned - Records/arrays, Up: Planned Features

11.2.3 Planned features: Files

Node: Planned - Other types, Next: , Previous: Planned - Files, Up: Planned Features

11.2.4 Planned features: Other types

Node: Planned - OOP, Next: , Previous: Planned - Other types, Up: Planned Features

11.2.5 Planned features: OOP

Node: Planned - Misc, Next: , Previous: Planned - OOP, Up: Planned Features

11.2.6 Planned features: Misc

Node: Planned - Utilities, Previous: Planned - Misc, Up: Planned Features

11.2.7 Planned features: Utilities

Node: Fixed Bugs, Previous: Planned Features, Up: To Do

11.3 Problems that have been solved

This section lists the bugs fixed since the last (non alpha/beta) GPC release, together with the date (YYYYMMDD) on which they were fixed, so you can check if some problem has already been solved in a recent release or developer version. For new features, see News.

Node: Internals, Next: , Previous: To Do, Up: Top

12 The GPC Source Reference

"The Source will be with you. Always."

This chapter describes internals of GPC. It is meant for GPC developers and those who want to become developers, or just want to know more about how the compiler works. It does not contain information needed to just use GPC to compile programs.

This chapter tells you how to look up additional information about the GNU Pascal compiler from its source code.

Please note: If you intend to modify GPC's source, please check the top of each file you're going to modify. A number of files are generated automatically by various tools. The top of these files will tell you by which tool and from what file they were generated. Modifying a generated file is pointless, since it will be overwritten the next time the tool is run. Instead, modify the original source (which will usually be easier in fact, e.g. a bison input file vs. the generated C code). This also holds for various documentation and other files.

Proprietary compilers often come with a lot of technical information about the internals of the compiler. This is necessary because their vendors want to avoid to distribute the source of the compiler - which is always the most definitive source of this technical information.

With GNU compilers, on the other hand, you are free to get the source code, look how your compiler works internally, customize it for your own needs, and to re-distribute it in modified or unmodified form. You may even take money for this redistribution. (For details, see the GNU General Public License, Copying.)

The following subsections are your guide to the GNU Pascal source code. If you have further questions, be welcome to ask them at the GNU Pascal mailing list (see Support).

All file paths mentioned in this chapter are relative to the GNU Pascal source directory, a subdirectory gcc/p below the top-level GCC source directory.

The following sections roughly coincide with the order of the steps a Pascal source passes through during compilation (omitting the code generation which is the job of the GCC backend, and the assembler and linker steps at the end which are done by the programs as and ld of binutils and possibly other utilities like collect2). Also missing here is the compiler driver gpc which behaves very similarly to gcc and whose main job is to invoke the other parts in the right order, with the right arguments etc.

Note, this chapter docuemnts only selected parts of the compiler. Many things are missing because nobody has yet had the time to write something about them. In any case, for real understanding of the inner workings, you should always refer to the source code.

For more information, see the manual of GCC internals, Top.

Node: Preprocessor, Next: , Up: Internals

12.1 The Pascal preprocessor

gpcpp is based on the C preprocessor, so it does everything cpp does (see the cpp manual) and some more. In particular:

Node: Lexical analyzer, Next: , Previous: Preprocessor, Up: Internals

12.2 GPC's Lexical Analyzer

The source files gpc-lex.c and pascal-lex.c contain the so-called lexical analyzer of the GNU Pascal compiler. The latter file was created using flex from pascal-lex.l. This very first stage of the compiler (after the preprocessor which is a separate executable) is responsible for reading what you have written and dividing it into tokens, the "atoms" of each computer language. The main entry point is the function, yylex which calls the flex-generated function lexscan which does the main work of token separation.

Here is, for example, where the real number 3.14 and the subrange of integers 3..14 are distinguished, and where strings constants, symbols etc. are recognized.

Node: Lexer problems, Next: , Up: Lexical analyzer

12.2.1 Lexer problems

Pascal is a language that's easy to lex and parse. Then came Borland ...

A number of their ad-hoc syntax extensions cause lexing or parsing problems, and even ambiguities. This lexer tries to solve them as well as possible, sometimes with clever rules, other times with gross hacks and with help from the parser. (And, BTW, it handles regular Pascal as well. ;-)

Some of the problems are:

Node: BP character constants, Next: , Previous: Lexer problems, Up: Lexical analyzer

12.2.2 BP character constants

Borland-style character constants of the form ^M need special care. For example look at the following type declaration: 

     type
       X = Integer;
       Y = ^X;        { pointer type }
       Z = ^X .. ^Y;  { subrange type }

One way to resolve this is to try to let the parser tell the lexer (via a global flag) whether a character constant or the symbol ^ (to create pointer types or to dereference pointer expressions) is suitable in the current context. This was done in previous versions, but it had a number of disadvantages: First, any dependency of the lexer on the parser (see Lexical Tie-Ins) is problematic by itself since it must be taken care of manually in each relevant parser rule. Furthermore, the parser read-ahead must be taken into account, so the flag must usually be changed apparently one token too early. Using a more powerful parsing algorithm such as GLR (see GLR Parsers) adds to this problem since it may read many tokens while the parser is split before it can perform any semantic action (which is where the flag could be modified). Secondly, as the example above shows, there are contexts in which both meanings are acceptable. So further look-ahead (within the lexer) was needed to resolve the problem.

Therefore, the current version of GPC uses another approach. When seeing ^X, the lexer returns two tokens, a regular ^ and a special token LEX_CARET_LETTER with semantic value X. The parser then accepts LEX_CARET_LETTER wherever an identifier is accepted (and turns it into the identifier X via the nonterminal caret_letter). Furthermore, it accepts the sequence ^, LEX_CARET_LETTER as a string constant (whose value is a one-character string). Since LEX_CARET_LETTER is only produced by the lexer immediately after ^ (no white-space in between), this works (whereas otherwise, pasting tokens in the parser is not reliable due to white-space, e.g. the token sequence : and = could stand for := (if := weren't a token by itself), but also for : = with a space in between). With this trick, we can handle ^ followed by a single letter or underscore. The fact that this doesn't cause any conflicts in the bison parser tell us that this method works.

However, BP even allows any other character after ^ as a char constant. E.g., ^) could be a pointer dereference after an expression and followed by a closing parenthesis, or the character i (sic!).

Some characters are unproblematic because they can never occur after a ^ in its regular meaning, so the sequence can be lexed as a char constant directly. These are all characters that are not part of any Pascal tokens at all (which includes all control characters except white-space, all non-ASCII characters and the characters !, &, %, ?, \, `, |, ~ and } - the last one occurs at the end of comments, but within a comment this issue doesn't occur, anyway) and those characters that can only start constants because a constant can never follow a ^ in Pascal (which are #, $, ', " and the digits).

For ^ followed by whitespace, we return the token LEX_CARET_WHITE which the parser accepts as either a string constant or equivalent to ^ (because in the regular meaning, the white-space is meaningless).

If ^ is followed by one of the tokens ,, ., :, ;, (, ), [, ], +, -, *, /, <, =, >, @, ^, the lexer just returns the tokens regularly, and the parser accepts these sequences as a char constant (besides the normal meaning of the tokens). (Again, since white-space after ^ is already dealt with, this token pasting works here.)

But ^ can also be followed by a multi-character alphanumeric sequence such as ^cto which might be read as ^ cto or ^c to (since BP also allows omitting white-space after constants), or by a multi-character token such as ^<= which could be ^ <= or ^< =. Both could be solved with extra tokens, e.g. lexing ^<= as ^, LEX_CARET_LESS, = and accepting ^, LEX_CARET_LESS in the parser as a string constant and LEX_CARET_LESS, = as equivalent to <= (relying on the fact that the lexer doesn't produce LEX_CARET_LESS if there's white-space after the < because then the simple ^, < will work, so justifying the token-pasting once again). This has not been done yet (in the alphanumeric case, this might add a lot of special tokens because of keywords etc., and it's doubtful whether that's worth it).

Finally, we have ^{ and ^(*. This is so incredibly stupid (e.g., think of the construct type c = Integer; foo = ^{ .. ^|; bar = {} c; which would become ambiguous then), that perhaps we should not attempt to handle this ...

(As a side-note, BP itself doesn't handle ^ character constants in many situations, including many that GPC does handle with the mechanisms described above, probably the clearest sign for a design bug. But if we support them at all, we might just as well do it better than BP ... :-)

Node: Compiler directives internally, Previous: BP character constants, Up: Lexical analyzer

12.2.3 Compiler directives internally

Compiler directives are mostly handled in options.c, mostly in common with command-line options, using the definitions in lang-options.h and the tables in gpc-options.h.

A special problem is that the parser sometimes has to read tokens before they're used to decide what to do next. This is generally harmless, but if there is a compiler directive before such a look-ahead token, it would be handled apparently too early. This looks strange from the programmer's point of view - even more so since the programmer cannot easily predict when the parser needs to read ahead and when not, and therefore cannot be sure where exactly to place the directive (especially for local directives that are meant to have a scope as small as possible).

To solve this problem (and in turn give the parser more freedom for further look ahead which is useful, e.g., for a GLR parser), GPC keeps the options that can be changed by directives in a struct options. There are several pointers to such a structure:

lexer_options are the options current to the lexer. These are always the ones read most recently. Compiler directives are applied here when read. Each directive creates a new struct options which is chained in a linked list to the previous ones.

compiler_options points to the options current for the compiler, i.e. seen before the last token handled in a parser rule. To facilitate this, we abuse Bison's location tracking feature (see Locations) and refer to the options seen before a token in the token's location (yylloc). Before each grammar rule is handled, the compiler options are updated to those of the last token involved in the rules handled so far, using Bison's YYLLOC_DEFAULT feature. Actual locations, used for error messages etc., are handled the same way (according to the real purpose of Bison's location tracking), also distinct for the lexer and compiler.

Note: Tokens are not always handled in order. E.g., in 2 + 3 * 4, first 3 * 4 is evaluated, then 2 + 12, i.e., the tokens 2 and + are handled after the following tokens. To avoid jumping back in the options, we store a counter, rather than a pointer, in yyloc, so we can compare it to the current counter. This also allows us to free any struct options that compiler_options has advanced beyond because it can never go back.

Finally, the pointer co points to the current options which is lexer_options when we're in the lexer and compiler_options otherwise. All routines that use or set options refer to co, so there is no problem when they may be called both from the lexer and from other parts of the compiler (e.g., lookup_name).

Note: Some of the options are flags declared in the backend. Since we can't keep them in struct option directly, we have to copy them back and forth in activate_options. This is a little annoyance, but no real problem.

Node: Language definition, Next: , Previous: Lexical analyzer, Up: Internals

12.3 Language Definition: GPC's Parser

The file parse.y contains the "bison" source code of GNU Pascal's parser. This stage of the compilation analyzes and checks the syntax of your Pascal program, and it generates an intermediate, language-independent code which is then passed to the GNU back-end.

The bison language essentially is a machine-readable form of the Backus-Naur Form, the symbolic notation of grammars of computer languages. "Syntax diagrams" are a graphical variant of the Backus-Naur Form.

For details about the "bison" language, see the Bison manual. A short overview how to pick up some information you might need for programming follows.

Suppose you have forgotten how a variable is declared in Pascal. After some searching in parse.y you have found the following: 

     simple_decl_1:
         ...
       | p_var variable_declaration_list
           { [...] }
       ;
     
     variable_declaration_list:
         variable_declaration { }
       | variable_declaration_list variable_declaration
       ;

Translated into English, this means: "A declaration can (amoung other things like types and constants, omitted here) consist of the keyword (lexical token) var followed by a `variable declaration list'. A `variable declaration list' in turn consists of one or more `variable declarations'." (The latter explanation requires that you understand the recursive nature of the definition of variable_declaration_list.)

Now we can go on and search for variable_declaration. 

     variable_declaration:
         id_list_limited ':' type_denoter_with_attributes
           { [...] }
         absolute_or_value_specification optional_variable_directive_list ';'
           { [...] }
       ;

The [...] are placeholders for some C statements, the semantic actions which (for the most part) aren't important for understanding GPC's grammar.

From this you can look up that a variable declaration in GNU Pascal consists of an identifier list, followed by a colon, "type denoter with attributes", an "absolute or value specification" and an "optional variable directive list", terminated by a semicolon. Some of these parts are easy to understand, the others you can look up from parse.y. Remember that the reserved word var precedes all this.

Now you know how to get the exact grammar of the GNU Pascal language from the source.

The semantic actions, not shown above, are in some sense the most important part of the bison source, because they are responsible for the generation of the intermediate code of the GNU Pascal front-end, the so-called tree nodes (which are used to represent most things in the compiler). For instance, the C code in "type denoter" returns (assigns to $$) information about the type in a variable of type tree.

The "variable declaration" gets this and other information in the numbered arguments ($1 etc.) and passes it to some C functions declared in the other source files. Generally, those functions do the real work, while the main job of the C statements in the parser is to call them with the right arguments.

This, the parser, is the place where it becomes Pascal.

Node: Parsing keywords, Next: , Up: Language definition

12.3.1 So many keywords, so many problems ...

Keywords can be potential problems since they are (generally) not available for use as identifiers. Only those keywords that are defined in ISO 7185 Pascal are unproblematic because no valid program should ever use them as identifiers.

To cope with this problem, GPC does several things:

The following sections describe the most problematic keywords:

These descriptions should make it clear that we're walking on the bleeding edge of what's possible with LALR(1) and lexer tricks. Trying much more will probably increase the complexity to the unmanageable.

Node: attribute as a weak keyword, Next: , Up: Parsing keywords

12.3.1.1 attribute as a weak keyword

Note that in the following we use the spelling attribute when referring to the directive and Attribute for an identifier. This is according to the GPCS and might make the following text clearer. However, it cannot be a criterion for resolving the conflict since the compiler must treat both spellings equally. The same applies, of course, to the line-breaks and white-space used here for readability.

Making attribute a weak keyword leads to a S/R conflict in variable declarations (whereas routine declarations go without conflicts). Consider this case: 

     var
       a: Integer; attribute (...)

vs. 

     var
       a: Integer;
       Attribute: ...

After reading the ;, the parser must decide whether to shift it, or to reduce to a variable declaration. But the next token attribute doesn't decide it, and bison can only look ahead one token.

The following token would resolve the problem, since the directive attribute is always followed by ( whereas an identifier in a variable declaration can be followed by , or :, but never (.

More generally, an identifier in an id_list in the parser can never be followed by ( (while identifiers in other contexts can be, e.g. in function calls). This must be carefully checked manually through the whole grammar!

Thus, the solution consists of two steps. Firstly, the lexer does the additional look-ahead that bison can't do. When it reads the word attribute (and it is not disabled by dialect options or by the user or shadowed by some declaration), then if the next token is not (, it can only be an identifier, so the lexer returns LEX_ID. If the next token is (, the lexer returns p_attribute.

Lexer look-ahead is not really nice, either, e.g. because it increases the "shift" of compiler directives. At least, we only have to read ahead two characters plus preceding white-space (two because of (.), and not an actual token - the latter would add additiional complications of saving and restoring lexer semantic values and the state of lexer/parser interrelation variables such as lex_const_equal, and then either lex the token again later or handle the cases where the parser modifies these variables in between. This would get really messy.

Secondly, the parser accepts p_attribute as an identifier except in an id_list. To achieve this, the nonterminal new_identifier_limited is used within id_list.

Note: Using new_identifier_limited does not mean that Attribute can't be used as an identifier in this place. Instead, this nonterminal can never be followed by (, so the lexer will have turned Attribute into a LEX_ID token already.

Actually, that's not all: In a constant_definition, the conflict is not against id_list, but against a simple new_identifier. But we can just use new_identifier_limited instead in the constant_definition rule.

This finally solves all conflicts with attribute. fjf792*.pas are test programs for these cases.

Node: external as a weak keyword, Next: , Previous: attribute as a weak keyword, Up: Parsing keywords

12.3.1.2 external as a weak keyword

The situation about external is similar to attribute. However, on the positive side, we don't have to worry about constants which cannot be external - by definition, since initialization and external declaration contradict each other.

The new problems are that an external directive can be followed by ;, name and by many more tokens if GPC will support a BP compatible external libname where libname can be a string constant expression.

So we have to consider the problem from the other side. In an id_list of a variable declaration (which is the only conflict, given the notes about attribute, attribute as a weak keyword.), an identifier can be followed only by , and :. These two tokens cannot follow an external directive (not even in external libname).

However, in other contexts, identifiers can be followed by other tokens (even in an id_list, e.g. procedure Foo (var External; i: Integer);), so we accept p_external as a new_identifier everywhere except in variable declarations (new_identifier_limited id_list_limited).

fjf793*.pas are test programs for external.

(Basically the same applies to the deprecated asmname.)

Node: forward near far, Next: , Previous: external as a weak keyword, Up: Parsing keywords

12.3.1.3 forward, near and far as weak keywords

forward is a little special in ISO 7185 in that it is no keyword, so it may be used as an identifier and a directive at the same time. That's more than what our weak keywords allow.

This problem would be easy to solve if we just parsed it as a plain identifier (LEX_ID) and then check that it was in fact forward.

However, the same applies to the BP directives near and far. (At least so it seems - the BP documentation claims they're reserved words, but the compiler seems to think otherwise.)

Parsing all the three together as an identifier and then checking which one it was fails because forward is a remote directive, i.e. a routine declared so has no body, while near and far are not. So it makes a syntactical difference for what follows.

So we need a new trick: We lex the three like regular (non-weak) keywords, but throw their tokens together with LEX_ID very early in the parser, in the id rule which is used everywhere an existing identifier is expected. But in the context of these three directives, no identifier is allowed, so the three tokens can be used without conflicts between each other or with id.

Node: implementation constructor destructor operator uses import initialization, Previous: forward near far, Up: Parsing keywords

12.3.1.4 implementation, constructor, destructor, operator, uses, import and initialization as weak keywords

In ISO 7185 Pascal, each section of the source code is uniquely introduced by a keyword (program, const, type, var, label, procedure, function, begin). However, the ending of some of these sections (in particular const, type and var) is not intrinsically defined, but only by the context (the next of these "critical" keywords). E.g., var Foo: Integer; can be a complete variable declaration part (if one of those keywords follows), or only a part of one, as in var Foo: Integer; Bar: Integer;. (For the other keywords, the ending is intrinsically defined - the program heading and label declarations end with the next ;. For procedure and function it's a little more complicated, due to forward declarations, but still well-defined, and begin ends with the matching end). The same applies to sections within one routine, except that program cannot occur there.

Extended Pascal adds to (in to begin do and to end do) and end (in interface modules and implementation modules without initializer and finalizer) to those "critical" keywords.

But it also adds two keywords which are not defined in classic Pascal, namely export and import. But they can only occur at the beginning of the source or of a module implementation so they have fewer chances to conflict with those other keywords. The same applies to UCSD/Borland Pascal's uses for units. (uses terminates at the first ;, export and import do not necessarily, like var etc.)

The problem gets bigger with UCSD/Borland Pascal's implementation in units. It can occur after the interface part, so it might follow, e.g., a variable declaration part. And it is not an ISO 7185 Pascal keyword.

If we want to treat implementation as a weak keyword, it must not conflict with new identifiers anywhere in the grammar.

However, variable declaration parts are not self-contained in the sense described above, so after a variable declaration part it is not immediately clear if the part is finished or will continue. So this is a place where a new identifier is acceptable. E.g.: 

     interface
     
     var
       Bar: Integer;
       Implementation: Integer;

vs. 

     interface
     
     var
       Bar: Integer;
     
     implementation

The same applies to implementation after const, type, export and import parts.

The same problem also occurs with the Borland Pascal and Object Pascal keywords constructor and destructor, the Borland Delphi keyword initialization, and the PXSC keyword operator since the respective declarations can follow variable declaration blocks etc. It also happens with import (but it is only possible after an export part) and with uses if we allow it after other declarations (GPC extension).

Again, we play some lexer tricks. We observe that the new identifier in export, var, const and type is always followed by either ,, : or = while none of the keywords implementation, constructor, destructor, operator, import and uses is ever followed by one of these symbols ... with two exceptions: operator = is valid, overloading the = operator. Consider: 

     type
       Foo = record end;
       Operator = (a, b);  { enum type }

vs. 

     type
       Foo = record end;
     
     operator = (a, b: Foo) c: Foo;

To decide whether operator is a keyword, we would have to look ahead six tokens! Anyway, that seems to be a new record (where "record" in this sentence can be read either as a Pascal keyword or in at least one of the usual English meanings ;-).

The other exception is that initialization can, in principle, be followed by (, as in: 

     implementation
     
     type
       Foo = Integer;
       Initialization (Obj: Integer)

vs. 

     implementation
     
     type
       Foo = Integer;
     
     Initialization
       (Obj as SubObj).Method;

This would require 3 tokens look-ahead. However, a ( at the beginning of a statement is quite uncommon, so we just disallow that, so the use of Initialization as an identifier is not restricted.

Doing so much look-ahead would be a huge effort and cause some complications as noted above. This seems inappropriate for such an academic example. So, until someone comes up with a clever trick to cope with this case, we give up here and let operator before = be a keyword, so overloading = is possible. This means that operator cannot be used as an export interface, a type or an (untyped) constant, unless the keyword is disabled explicitly or by dialect options. (Enabling and disabling the keyword by the parser would also have been no option here, since the parser would need the 6-token look-ahead just as well, which it cannot do.)

You may have noticed that we "forgot" import (in the list of possibly unfinished sections; not in the list of critical following keywords where it was alright; it actually plays both roles in this discussion).

This is because the identifier at the beginning of an import specification can be followed by qualified, only, in, ( or ; - the former two of which are non-standard keywords as well and would therefore conflict with a new identifier after, e.g., uses and operator.

This means that there's no simple general solution. So let's consider the problematic keywords after an import part in detail:

We forbid all of these keywords immediately after an import part. This is achieved using parser precedence rules.

Node: Parsing subranges, Previous: Parsing keywords, Up: Language definition

12.3.2 Expressions as lower bounds of subranges

Extended Pascal allows arbitrary expressions as the lower bounds of subrange types. This leads to some following parsing difficulties: 

     type
       a = (expr1) .. expr2;

(if expr1 starts with an identifier) vs. 

     type
       a = (enum1, enum2);

If the enum type contains at least two items, we get no real conflicts, but what the bison manual calls "mystery conflicts", i.e. our grammer is LR(1), but not LALR(1) which bison requires, Mystery Conflicts.

Our solution is the one suggested in the bison manual, to add a bogus rule. For that we add a new terminal BOGUS which is never used and a new nonterminal conflict_id which contains the identifiers that are responsible for the six conflicts.

It gets more difficult if the enum type has only one item, i.e.: 

     type
       a = (enum1);

If further expr1 consists of a single identifier, the conflict cannot be resolved without reading the token following the right parenthesis. (This is inherent in the EP language.)

But already after reading the identifier (expr1 or enum1), our parser has to decide whether to reduce it to an expression or to keep it as an identifier. (The alternative would be to define an expression which is anything but a single identifier, and parse (identifier) as a distinct thing, but this would get quite hairy.)

We resolve it with a lexer hack. The lexer turns a right parenthesis which is followed by .. into the new token LEX_RPAR. Most places in the parser treat LEX_RPAR and ) as equivalent (nonterminal rpar). However, enum types allow only ) (they can never be followed by ..), and the lower bound of a subrange allows only LEX_RPAR (it is always followed by ..). This resolves the conflict.

But there are more conflicts if the lower bound is not enclosed in parentheses: 

     type
       a = Foo (42) .. expr2;

(where Foo can be one of certain built-in functions such as Sqr, or a type name for a type-cast) vs. 

     type
       a = Bar (42);

(where Bar is an undiscriminated schema type).

To resolve this, we let the lexer return a special token LEX_SCHEMA for identifiers which correspond to undiscriminated schema types. The parser accepts this token in new_identifier (so schema identifiers can be redefined) and typename (e.g. for parameters), but not in id (which appears in expressions) where undiscriminated schema types are invalid.

The last conflict: 

     type
       a = @Foo = (expr) .. expr2;

(where @ is the BP address operator - the = (expr) is there to create an ordinal (namely, Boolean) expression that starts with the address operator) vs. 

     type
       a = @Bar = (expr);

(where @ is a lexical alternative for ^, according to the standards).

The conflict arises already with the @ token. The = (as a comparison operator in the first case, and for a type initializer - EP extension, combined with a BP extension of using = instead of value) just adds to the problem. Since expr can be arbitrary long, the conflict is in fact not solvable with any fixed number of lookup tokens.

This conflict is decided using parser precedence rules, in favour of the latter interpretation. (BP itself can't parse the supposedly BP compatible former syntax.)

Another parsing problem is the innocent-looking (BP compatible) New call for objects with constructors: 

     New (ObjectPointer, ConstructorCall (Arguments))

This conflicts with: 

     New (SchemaPointer, FunctionCall (Arguments))

The same goes for Dispose with destructors. Since the constructor name is used without naming the object type, it needs special handling. Trying to solve it using pascal_shadow_record_fields (which is used to handle with statements and the implicit Self parameter in object methods), fails for two reasons: First, only constructors (or destructors, respectively), no other methods, must be recognized. This could be solved with a special flag to pascal_shadow_record_fields.

But secondly, the constructor must be recognized only in the first position of the second argument (see fjf915[ab].pas for some evil examples). This means the same identifier (here: Init) can have a different meaning in different positions of the same statement. This is completely contrary to the usual Pascal scoping rules, but actually BP's behaviour.

Since the two forms of New shown above look completely the same syntactically (the difference is given by the type, i.e. the semantic value, of the first argument of New), we can't distinguish them during parsing without further tricks.

Using a GLR parser, the %merge feature looked promising, but it also does not help here since it first evaluates both alternatives and then merges them (in a user-defined way, which would be fine since it could look at the type). But trying to evaluate the respective wrong alternative would already produce error messages which can't be undone later.

So we resort to a lexical tie-in. After parsing the first argument (start_of_new), we store it in the global variable current_structor_object_type which the lexer recognizes and returns the special token LEX_STRUCTOR for the first following occurrence of an identifier that denotes a constructor/destructor of this object type. This token is then required in the syntax rules for an object New call with a constructor (whereas an object New call without constructor is parsed the same way as a non-object New call).

To avoid mis-parsing, we accept LEX_STRUCTOR nowhere else in the grammar, and in the rule for New call with further arguments which are not a constructor, we verify that the first argument is no object (otherwise something like New (ObjectPointer, SomeFunction) could be accepted syntactially and cause havoc in the further stages).

This method has all the usual drawbacks of lexer tie-ins, in particular it would break if the parser had already read ahead too far when the first argument of New is handled (which is in principle not impossible with GLR). On the other hand, that's the same when the lexer looks at declarations, which include identifiers made available by with, so this new kludge is at least no worse than a with based alternative (if the latter would work at all).

Node: Tree nodes, Next: , Previous: Language definition, Up: Internals

12.4 Tree Nodes

If you want really to understand how the GNU Pascal language front-end works internally and perhaps want to improve the compiler, it is important that you understand GPC's internal data structures.

The data structure used by the language front-end to hold all information about your Pascal program are the so-called "tree nodes". (Well, it needn't be Pascal source - tree nodes are language independent.) The tree nodes are kind of objects, connected to each other via pointers. Since the GNU compiler is written in C and was created at a time where nobody really thought about object-oriented programming languages yet, a lot of effort has been taken to create these "objects" in C.

Here is an extract from the "object hierarchy". Omissions are marked with "..."; nodes in parentheses are "abstract": They are never instantiated and aren't really defined. They only appear here to clarify the structure of the tree node hierarchy. The complete list is in ../tree.def; additional information can be found in ../tree.h. 

     (tree_node)
     |
     |--- ERROR_MARK  { enables GPC to continue after an error }
     |
     |--- (identifier)
     |    |
     |    |--- IDENTIFIER_NODE
     |    |
     |    \--- OP_IDENTIFIER
     |
     |--- TREE_LIST  { a list of nodes, also used as a
     |                  general-purpose "container object" }
     |
     |--- TREE_VEC
     |
     |--- BLOCK
     |
     |--- (type)  { information about types }
     |    |
     |    |--- VOID_TYPE
     |    |
     |    |--- INTEGER_TYPE
     |   ...
     |    |
     |    |--- RECORD_TYPE
     |    |
     |    |--- FUNCTION_TYPE
     |    |
     |    \--- LANG_TYPE  { for language-specific extensions }
     |
     |--- INTEGER_CST  { an integer constant }
     |
     |--- REAL_CST
     |
     |--- STRING_CST
     |
     |--- COMPLEX_CST
     |
     |--- (declaration)
     |    |
     |    |--- FUNCTION_DECL
     |   ...
     |    |
     |    |--- TYPE_DECL
     |    |
     |    \--- VAR_DECL
     |
     |--- (reference)
     |    |
     |    |--- COMPONENT_REF
     |   ...
     |    |
     |    \--- ARRAY_REF
     |
     |--- CONSTRUCTOR
     |
     \--- (expression)
          |
          |--- MODIFY_EXPR  { assignment }
          |
          |--- PLUS_EXPR  { addition }
         ...
          |
          |--- CALL_EXPR  { procedure/function call }
          |
          |--- GOTO_EXPR
          |
          \--- LOOP_EXPR  { for all loops }

Most of these tree nodes - struct variables in fact - contain pointers to other tree nodes. A TREE_LIST for instance has a TREE_VALUE and a TREE_PURPOSE slot which can contain arbitrary data; a third pointer TREE_CHAIN points to the next TREE_LIST node and thus allows us to create linked lists of tree nodes.

One example: When GPC reads the list of identifiers in a variable declaration 

     var
       Foo, Bar, Baz: Integer;

the parser creates a chain of TREE_LISTs whose TREE_VALUEs hold IDENTIFIER_NODEs for the identifiers Foo, Bar, and Baz. The function declare_variables() (declared in declarations.c) gets this tree list as a parameter, does some magic, and finally passes a chain of VAR_DECL nodes to the back-end.

The VAR_DECL nodes in turn have a pointer TREE_TYPE which holds a _TYPE node - an INTEGER_TYPE node in the example above. Having this, GPC can do type-checking when a variable is referenced.

For another example, let's look at the following statement: 

     Baz := Foo + Bar;

Here the parser creates a MODIFY_EXPR tree node. This node has two pointers, TREE_OPERAND[0] which holds a representation of Baz, a VAR_DECL node, and TREE_OPERAND[1] which holds a representation of the sum Foo + Bar. The sum in turn is represented as a PLUS_EXPR tree node whose TREE_OPERAND[0] is the VAR_DECL node Foo, and whose TREE_OPERAND[1] is the VAR_DECL node Bar. Passing this (the MODIFY_EXPR node) to the back-end results in assembler code for the assignment.

If you want to have a closer look at these tree nodes, write a line {$debug-tree FooBar} into your program with FooBar being some identifier in your program. This tells GPC to output the contents of the IDENTIFIER_NODE to the standard error file handle in human-readable form.

While hacking and debugging GPC, you will also wish to have a look at these tree nodes in other cases. Use the debug_tree() function to do so. (In fact {$debug-tree FooBar} does nothing else than to debug_tree() the IDENTIFIER_NODE of the Foobar identifier node - note the capitalization of the first character in the internal representation.)

Node: Parameter passing, Next: , Previous: Tree nodes, Up: Internals

12.5 Parameter Passing

GPC supports a lot of funny things in parameter lists: value and reference, protected and const parameters, strings and other schemata with specified or unspecified discriminants, conformant and open arrays, objects, procedural parameters, untyped reference parameters, etc. All this requires sophisticated type-checking; the responsible function is convert_arguments() in the source file typecheck.c. Every detail can be looked up from there.

Some short notes about the most interesting cases follow.


Conformant arrays:
First, the array bounds are passed (an even number of parameters of an ordinal type), then the address(es) of the array(s) themselves.
Procedural parameters:
These need special care because a function passed as a parameter can be confused with a call to the function whose result is then passed as a parameter. See also the functions maybe_call_function() and probably_call_function() in expressions.c.
Chars:
According to ISO 10206 Extended Pascal, formal char parameters accept string values. GPC does the necessary conversion implicitly. The empty string produces a space.
Strings and schemata:
Value parameter strings and schemata of known size are really passed by value. Value parameter strings and schemata of unknown size are passed by reference, and GPC creates temporary variable to hold a copy of the string.
CString parameters:
GPC implicitly converts any string value such that the address of the actual string data is passed and appends a Chr (0) terminator when necessary.
const parameters:
If a constant value is passed to a const parameter, GPC assigns the value to a temporary variable whose address is passed. Exception: Small types (whose size is known and not bigger than that of a pointer) as well as all integer, real and complex types are passed by value.
Untyped parameters:
These are denoted by var foo or var foo: Void and are compatible to C's void * parameters; the size of such entities is not passed. Maybe we will change this in the future and pass the size for var foo parameters whereas var foo: Void will remain compatible to C. (Same with const instead of var.)

Node: GPI files, Next: , Previous: Parameter passing, Up: Internals

12.6 GPI files - GNU Pascal Interfaces

This section documents the mechanism how GPC transfers information from the exporting modules and units to the program, module or unit which imports (uses) the information.

A GPI file contains a precompiled GNU Pascal interface. "Precompiled" means in this context that the interface already has been parsed (i.e. the front-end has done its work), but that no assembler output has been produced yet.

The GPI file format is an implementation-dependent (but not too implementation-dependent ;-) file format for storing GNU Pascal interfaces to be exported - Extended Pascal and PXSC module interfaces as well as interface parts of UCSD/Borland Pascal units compiled with GNU Pascal.

To see what information is stored in or loaded from a GPI file, run GPC with an additional command-line option --debug-gpi. Then, GPC will write a human-readable version of what is being stored/loaded to the standard error file handle. (See also: Tree nodes.) Please note: This will usually produce huge amounts of output!

While parsing an interface, GPC stores the names of exported objects in tree lists - look for handle_autoexport in the GPC source files. At the end of the interface, everything is stored in one or more GPI files. This is done in module.c. There you can find the source of create_gpi_files() which documents the file format:

First, a header of 33 bytes containing the string GNU Pascal unit/module interface plus a newline.

This is followed by an integer containing the "magic" value 12345678 (hexadecimal) to carry information about the endianness. Note that, though a single GPI file is always specific to a particular target architecture, the host architecture (i.e., the system on which GPC runs) can be different (cross-compilers). Currently, GPC is not able to convert endianness in GPI files "on the fly", but at least it will detect and reject GPI files with the "wrong" endianness. When writing GPI files, always the host's endianness is used (this seems to be a good idea even when converting on the fly will be supported in the future, since most often, GPI files created by a cross-compiler will be read again by the same cross-compiler). "Integer" here and in the following paragraphs means a gpi_int (which is currently defined as HOST_WIDE_INT).

The rest of the GPI file consists of chunks. Each chunk starts with a one-byte code that describes the type of the chunk. It is followed by an integer that specifies the size of the chunk (excluding this chunk header). The further contents depend on the type, as listed below.

For the numeric values of the chunk type codes, please refer to GPI_CHUNKS in module.c. Chunk types denoted with (*) must occur exactly once in a GPI file. Other types may occur any number of times (including zero times). The order of chunks is arbitrary. "String" here simply means a character sequence whose length is the chunk's length (so no terminator is needed).

GPI_CHUNK_VERSION (String) (*)
The version of the GPI file which is the same as the GPC version. If USE_GPI_DEBUG_KEY is used (which will insert a "magic" value at the beginning of each node in the node table, see below, so errors in GPI files will be detected more reliably), D is appended to this version string. (Currently, USE_GPI_DEBUG_KEY is used by default.) Furthermore, the GCC backend version is appended, since it also influences GPI files.
GPI_CHUNK_TARGET (String) (*)
The target system the GPI file was compiled for.
GPI_CHUNK_MODULE_NAME (String) (*)
The name of the unit/module.
GPI_CHUNK_SRCFILE (String) (*)
The name of the primary source file of the unit/module.
GPI_CHUNK_IMPORT
The name of an interface imported by the current interface. This chunk consists of a string followed by the checksum of the imported interface's nodes, so the chunk length is the length of the string plus the size of an integer. Again, no terminator of the string is needed.

The checksum is currently a simple function of the contents of the GPI_CHUNK_NODES chunk's contents (see below). This might be replaced in the future by a MD5 hash or something else more elaborate.

GPI_CHUNK_LINK (String)
The name of a file to link.
GPI_CHUNK_LIB (String)
The name of a library to link (prefixed with -l).
GPI_CHUNK_INITIALIZER (String)
The name of a module initializer. For technical reasons, any such chunk must come after the GPI_CHUNK_MODULE_NAME chunk.
GPI_CHUNK_GPC_MAIN_NAME (String)
A gpc-main option given in this interface. (More than one occurrence is pointless.)
GPI_CHUNK_NODES (*)
The exported names and the objects (i.e., constants, data types, variables and routines) they refer to are internally represented as so-called tree nodes as defined in the files ../tree.h and ../tree.def from the GNU compiler back-end. (See also: Tree nodes.)

The main problem when storing tree nodes is that they form a complicated structure in memory with a lot of circular references (actually, not a tree, but a directed graph in the usual terminology, so the name "tree nodes" is actually a misnomer), so the storing mechanism must make sure that nothing is stored multiple times.

The functions load_node() and store_node_fields() do the main work of loading/storing the contents of a tree node with references to all its contained pointers in a GPI file. Each tree node has a TREE_CODE indicating what kind of information it contains. Each kind of tree nodes must be stored in a different way which is not described here. See the source of these functions for details.

As most tree nodes contain pointers to other tree nodes, load_node() is an (indirectly) recursive function. Since this recursion can be circular (think of a record containing a pointer to a record of the same type), we must resolve references to tree nodes which already have been loaded. For this reason, all tree nodes being loaded are kept in a table (rb.nodes). They are entered there before all their fields have been loaded (because loading them is what causes the recursion). So the table contains some incomplete nodes during loading, but at the end of loading a GPI file, they have all been completed.

On the other hand, for store_node_fields() the (seeming) recursion must be resolved to an iterative process so that the single tree nodes are stored one after another in the file, and not mixed together. This is the job of store_tree(). It uses a hash table (see get_node_id()) for efficiency.

When re-exporting (directly or indirectly) a node that was imported from another interface, and a later compiler run imports both interfaces, it must merge the corresponding nodes loaded from both interfaces. Otherwise it would get only similar, but not identical items. However, we cannot simply omit the re-exported nodes from the new interface in case a later compiler run imports only one of them. The same problem occurs when a module exports several interfaces. In this case, a program that imports more than one of them must recognize their contents as identical where they overlap.

Therefore, each node in a GPI file is prefixed (immediately before its tree code) with information about the interface it was originally imported from or stored in first. This information is represented as a reference to an INTERFACE_NAME_NODE followed by the id (as an integer) of the node in that interface. If the node is imported again and re-re-exported, this information is copied unchanged, so it will always refer to the interface the node was originally contained it. For nodes that appear in an interface for the first time (the normal case), a single 0 integer is stored instead of interface INTERFACE_NAME_NODE and id (for shortness, since this information is implicit).

This mechanism is not applied to INTERFACE_NAME_NODEs since there would be a problem when the identifier they represent is the name of the interface they come from; neither to IDENTIFIER_NODEs because they are handled somewhat specially by the backend (e.g., they contain fields like IDENTIFIER_VALUE which depend on the currently active declarations, so storing and loading them in GPI files would be wrong) because there is only one IDENTIFIER_NODE ever made for any particular name. But for the same reason, it is no problem that the mechanism can't be applied to them.

INTERFACE_NAME_NODEs are a special kind of tree nodes, only used for this purpose. They contain the name of the interface, the name of the module (to detect the unlikely case that different modules have interfaces of the same name which otherwise might confuse GPC), and the checksum of that interface. The latter may seem redundant with the checksum stored in the GPI_CHUNK_IMPORT chunk, but in fact it is not. On the one hand, GPI_CHUNK_IMPORT chunks occur only for interfaces imported directly, while the INTERFACE_NAME_NODE mechanism might also refer to interfaces imported indirectly. On the other hand, storing the checksum in the GPI_CHUNK_IMPORT chunks allows the automake mechanism to detect discrepancies and force recompilation of the imported module, whereas during the handling of the GPI_CHUNK_NODES chunk, the imported modules must already have been loaded. (It would be possible to scan the GPI_CHUNK_NODES chunk while deciding whether to recompile, but that would be a lot of extra effort, compared to storing the checksum in the GPI_CHUNK_IMPORT chunks.)

Finally, at the end of the GPI_CHUNK_NODES chunk, a checksum of its own contents (excluding the checksum itself, of course) is appended. This is to detect corrupted GPI files and is independent of the other uses of checksums.

GPI_CHUNK_OFFSETS (*)
An offset table for the tree nodes. Each node in a GPI file is assigned a unique id (which is stored as an integer wherever nodes refer to other nodes). There are some special tree nodes (e.g., integer_type_node or NULL_TREE) which are used very often and have fixed meanings. They have been assigned predefined ids, so they don't have to be stored in the GPI file at all. Their number and values are fixed (but may change between different GPC versions), see SPECIAL_NODES in module.c.

For the remaining nodes, the GPI_CHUNK_OFFSETS table contains the file offsets as integers where they are stored within the (only) GPI_CHUNK_NODES chunk. The offsets are relative to the start of that chunk, i.e. after the chunk header. After the table (but still in this chunk) the id of the main node which contains the list of all exported names is stored as an integer. (Currently, this is always the last node, but for the file format definition, this is not guaranteed.)

GPI_CHUNK_IMPLEMENTATION
This chunk contains no data (i.e., its size must be 0). Its only purpose is to signal that the module implementation or the implementation part of the unit has been compiled. (Stored, but not used currently.)

That's it. Now you should be able to "read" GPI files using GPC's --debug-gpi option. There is also a utility gpidump (built and installed with GPC, source code in the utils directory) to decode and show the contents of GPI files. It does also some amount of integrity checking (a little more than GPC does while loading GPI files), so if you suspect a problem with GPI files, you might want to run gpidump on them, discarding its standard output (it writes all error reports to standard error, of course).

If you encounter a case where the loaded information differs too much from the stored information, you have found a bug - congratulations! What "too much" means, depends on the object being stored in or loaded from the GPI file. Remember that the order things are loaded from a GPI file is the reversed order things are stored when considering different recursion levels, but the same order when considering the same recursion level. (This is important when using --debug-gpi; with gpidump you can read the file in any order you like.)

Node: Automake, Next: , Previous: GPI files, Up: Internals

12.7 GPC's Automake Mechanism - How it Works

When a program/module/unit imports (uses) an interface, GPC searches for the GPI file (see GPI files) derived from the name of the interface.

Case 1: A GPI file was found.

Each GPI file contains the name of the primary source file (normally a .pas or .p file) of the module/unit, and the names of all interfaces imported. GPC reads this information and invokes itself with a command like 

     gpc foo.pas -M -o foo.d

This means: preprocess the file, and write down the name of the object file and those of all its source files in foo.d. GPC reads foo.d and looks if the object file exists and if the source was modified since the creation of the object file and the gpi file. If so, GPC calls itself again to compile the primary source file. When everything is done, the .d file is removed. If there was no need to recompile, all interfaces imported by the module/unit are processed in the same way as this one.

Case 2: No GPI file was found.

In this case, GPC derives the name of the source file from that of the interface by trying first interface.p, then interface.pas. This will almost always work with UCSD/Borland Pascal units, but not always with Extended Pascal modules. The programmer can override this assumption using uses ... in or import ... in.

All this is done by the function gpi_open() which uses some auxiliary functions such as module_must_be_recompiled() and compile_module().

Each time an object file is compiled or recognized as being up-to-date, its name is stored in a temporary file with the same base name as all the other temporary files used by GPC but the extension .gpc. When the top-level gpc is invoked (which calls gpc1 later on), it passes the name of this temporary file as an additional command line parameter to gpc1. After compilation has been completed, the top-level gpc reads the temporary file and adds the new object files to the arguments passed to the linker.

The additional command --amtmpfile (not to be specified by the user!) is passed to child GPC processes, so all compiles use the same temporary file.

The source for this is merely in module.c, but there are also some hacks in gpc.c, additional command line options in lang-options.h and options.c, and gpc.h contains declarations for the functions and global variables.

Node: File Layout, Next: , Previous: Automake, Up: Internals

12.8 Files that make up GPC

The GNU back end (gbe) is used to convert RTL into assembler code. It is supposed to be language independent. Files are in the .. directory (i.e., the directory called gcc). It also uses files in the ../config subdirectories etc.

Unfortunately, some of them are not completely language independent and need patching for GPC. These patches (against all supported GCC versions) are in the diffs subdirectory.

The Pascal language implementation files are in the directory called p. Some of them were written from scratch. Others are hacked from GCC sources. Their roots, if any, are mentioned in the comment at their top.

Node: Planned, Previous: File Layout, Up: Internals

12.9 Planned features

AnyStrings

     GetCapacity (s):
       LongString            : s.Capacity
       UndiscriminatedString : MaxInt
       ShortString           : High (s)
       FixedString           : High (s) - Low (s) + 1
       CString (Array)       : High (s) - Low (s)
       CString (Zeiger)      : strlen (s)
       ObjectString          : s.GetCapacity
     
     GetLength (s):
       LongString            : s.Length
       UndiscriminatedString : s.Length
       ShortString           : Ord (s[0])
       FixedString           : c := High (s);
                               while (c >= Low (s)) and (s[c] = ' ') do Dec (c);
                               c - Low (s) + 1
       CString               : strlen (s)
       ObjectString          : s.GetLength
     
     SetLength (s,n):
       if n > GetCapacity (s) then
         if TruncateFlag then
           n := GetCapacity (s)
         else
           Error;
       LongString            : s.Length := n
       UndiscriminatedString : if n > s.Capacity then
                                 begin
                                   tmp := @s;
                                   { possibly round n up to m * 2^k
                                     to avoid frequent reallocations }
                                   New (@s, n);
                                   Move (tmp^[1], s[1], Length (tmp^);
                                   Dispose (tmp)
                                 end;
                               s.Length := n
       ShortString           : s[0] := Chr (n)
       FixedString           : FillChar (s[Low (s) + n],
                                 GetCapacity (s) - n, ' ')
       CString               : s[n] := #0
       ObjectString          : s.SetLength (n)
     
     GetFirstChar (s):
       LongString            : @s[1]
       UndiscriminatedString : @s[1]
       ShortString           : @s[1]
       FixedString           : @s[Low (s)]
       CString               : s
       ObjectString          : s.GetFirstChar

Anything else can be reduced to these, e.g. string assignment: 

     SetLength (Dest, GetLength (Src));
     Move (GetFirstChar (Src) ^, GetFirstChar (Dest) ^, GetLength (Dest));
                                                                   ^^^^
                                                    (because of truncate!)

Note pointer CStrings because assignments to them (from long, undiscriminated (with appending #0) or CStrings, not from short, fixed or object strings) should set the pointer, not overwrite the memory pointed to.

Fully automatic C header translator

Node: Copying, Next: , Previous: Internals, Up: Top

Appendix A GNU GENERAL PUBLIC LICENSE

Version 2, June 1991
     Copyright © 1989, 1991 Free Software Foundation, Inc.
     59 Temple Place -- Suite 330, Boston, MA 02111-1307, USA
     
     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.

GPL Preamble

The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software - to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation's software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Lesser General Public License instead.) You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.

To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.

We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.

Also, for each author's protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors' reputations.

Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone's free use or not licensed at all.

The precise terms and conditions for copying, distribution and modification follow.

  1. This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The "Program", below, refers to any such program or work, and a "work based on the Program" means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term "modification".) Each licensee is addressed as "you".

    Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does.

  2. You may copy and distribute verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any other recipients of the Program a copy of this License along with the Program.

    You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.

  3. You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions:
    1. You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change.
    2. You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License.
    3. If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this License. (Exception: if the Program itself is interactive but does not normally print such an announcement, your work based on the Program is not required to print an announcement.)

    These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

    Thus, it is not the intent of this section to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Program.

    In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.

  4. You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following:
    1. Accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,
    2. Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,
    3. Accompany it with the information you received as to the offer to distribute corresponding source code. (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer, in accord with Subsection b above.)

    The source code for a work means the preferred form of the work for making modifications to it. For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable. However, as a special exception, the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable.

    If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code.

  5. You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.
  6. You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Program or its derivative works. These actions are prohibited by law if you do not accept this License. Therefore, by modifying or distributing the Program (or any work based on the Program), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Program or works based on it.
  7. Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions. You may not impose any further restrictions on the recipients' exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties to this License.
  8. If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Program at all. For example, if a patent license would not permit royalty-free redistribution of the Program by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Program.

    If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances.

    It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice.

    This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License.

  9. If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License.
  10. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

    Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and "any later version", you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation.

  11. If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally.
  12. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
  13. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

How to Apply These Terms to Your New Programs

If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.

To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the "copyright" line and a pointer to where the full notice is found. 

     one line to give the program's name and a brief idea of what it does.
     Copyright (C) year  name of author
     
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 2 of the License, or
     (at your option) any later version.
     
     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
     GNU General Public License for more details.
     
     You should have received a copy of the GNU General Public License
     along with this program; if not, write to the Free Software
     Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

Also add information on how to contact you by electronic and paper mail.

If the program is interactive, make it output a short notice like this when it starts in an interactive mode: 

     Gnomovision version 69, Copyright (C) year name of author
     Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
     type `show w'.
     This is free software, and you are welcome to redistribute it
     under certain conditions; type `show c' for details.

The hypothetical commands show w and show c should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than show w and show c; they could even be mouse-clicks or menu items - whatever suits your program.

You should also get your employer (if you work as a programmer) or your school, if any, to sign a "copyright disclaimer" for the program, if necessary. Here is a sample; alter the names: 

     Yoyodyne, Inc., hereby disclaims all copyright interest in the program
     `Gnomovision' (which makes passes at compilers) written by James Hacker.
     
     signature of Ty Coon, 1 April 1989
     Ty Coon, President of Vice

This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Lesser General Public License instead of this License.

Node: Library Copying, Next: , Previous: Copying, Up: Top

Appendix B GNU LESSER GENERAL PUBLIC LICENSE

Version 2.1, February 1999
     Copyright © 1991, 1999 Free Software Foundation, Inc.
     59 Temple Place -- Suite 330, Boston, MA 02111-1307, USA
     
     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.
     
     [This is the first released version of the Lesser GPL.  It also counts
     as the successor of the GNU Library Public License, version 2, hence the
     version number 2.1.]

LGPL Preamble

The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public Licenses are intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users.

This license, the Lesser General Public License, applies to some specially designated software--typically libraries--of the Free Software Foundation and other authors who decide to use it. You can use it too, but we suggest you first think carefully about whether this license or the ordinary General Public License is the better strategy to use in any particular case, based on the explanations below.

When we speak of free software, we are referring to freedom of use, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish); that you receive source code or can get it if you want it; that you can change the software and use pieces of it in new free programs; and that you are informed that you can do these things.

To protect your rights, we need to make restrictions that forbid distributors to deny you these rights or to ask you to surrender these rights. These restrictions translate to certain responsibilities for you if you distribute copies of the library or if you modify it.

For example, if you distribute copies of the library, whether gratis or for a fee, you must give the recipients all the rights that we gave you. You must make sure that they, too, receive or can get the source code. If you link other code with the library, you must provide complete object files to the recipients, so that they can relink them with the library after making changes to the library and recompiling it. And you must show them these terms so they know their rights.

We protect your rights with a two-step method: (1) we copyright the library, and (2) we offer you this license, which gives you legal permission to copy, distribute and/or modify the library.

To protect each distributor, we want to make it very clear that there is no warranty for the free library. Also, if the library is modified by someone else and passed on, the recipients should know that what they have is not the original version, so that the original author's reputation will not be affected by problems that might be introduced by others.

Finally, software patents pose a constant threat to the existence of any free program. We wish to make sure that a company cannot effectively restrict the users of a free program by obtaining a restrictive license from a patent holder. Therefore, we insist that any patent license obtained for a version of the library must be consistent with the full freedom of use specified in this license.

Most GNU software, including some libraries, is covered by the ordinary GNU General Public License. This license, the GNU Lesser General Public License, applies to certain designated libraries, and is quite different from the ordinary General Public License. We use this license for certain libraries in order to permit linking those libraries into non-free programs.

When a program is linked with a library, whether statically or using a shared library, the combination of the two is legally speaking a combined work, a derivative of the original library. The ordinary General Public License therefore permits such linking only if the entire combination fits its criteria of freedom. The Lesser General Public License permits more lax criteria for linking other code with the library.

We call this license the Lesser General Public License because it does Less to protect the user's freedom than the ordinary General Public License. It also provides other free software developers Less of an advantage over competing non-free programs. These disadvantages are the reason we use the ordinary General Public License for many libraries. However, the Lesser license provides advantages in certain special circumstances.

For example, on rare occasions, there may be a special need to encourage the widest possible use of a certain library, so that it becomes a de-facto standard. To achieve this, non-free programs must be allowed to use the library. A more frequent case is that a free library does the same job as widely used non-free libraries. In this case, there is little to gain by limiting the free library to free software only, so we use the Lesser General Public License.

In other cases, permission to use a particular library in non-free programs enables a greater number of people to use a large body of free software. For example, permission to use the GNU C Library in non-free programs enables many more people to use the whole GNU operating system, as well as its variant, the GNU/Linux operating system.

Although the Lesser General Public License is Less protective of the users' freedom, it does ensure that the user of a program that is linked with the Library has the freedom and the wherewithal to run that program using a modified version of the Library.

The precise terms and conditions for copying, distribution and modification follow. Pay close attention to the difference between a "work based on the library" and a "work that uses the library". The former contains code derived from the library, whereas the latter must be combined with the library in order to run.

  1. This License Agreement applies to any software library or other program which contains a notice placed by the copyright holder or other authorized party saying it may be distributed under the terms of this Lesser General Public License (also called "this License"). Each licensee is addressed as "you".

    A "library" means a collection of software functions and/or data prepared so as to be conveniently linked with application programs (which use some of those functions and data) to form executables.

    The "Library", below, refers to any such software library or work which has been distributed under these terms. A "work based on the Library" means either the Library or any derivative work under copyright law: that is to say, a work containing the Library or a portion of it, either verbatim or with modifications and/or translated straightforwardly into another language. (Hereinafter, translation is included without limitation in the term "modification".)

    "Source code" for a work means the preferred form of the work for making modifications to it. For a library, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the library.

    Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running a program using the Library is not restricted, and output from such a program is covered only if its contents constitute a work based on the Library (independent of the use of the Library in a tool for writing it). Whether that is true depends on what the Library does and what the program that uses the Library does.

  2. You may copy and distribute verbatim copies of the Library's complete source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and distribute a copy of this License along with the Library.

    You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.

  3. You may modify your copy or copies of the Library or any portion of it, thus forming a work based on the Library, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions:
    1. The modified work must itself be a software library.
    2. You must cause the files modified to carry prominent notices stating that you changed the files and the date of any change.
    3. You must cause the whole of the work to be licensed at no charge to all third parties under the terms of this License.
    4. If a facility in the modified Library refers to a function or a table of data to be supplied by an application program that uses the facility, other than as an argument passed when the facility is invoked, then you must make a good faith effort to ensure that, in the event an application does not supply such function or table, the facility still operates, and performs whatever part of its purpose remains meaningful.

      (For example, a function in a library to compute square roots has a purpose that is entirely well-defined independent of the application. Therefore, Subsection 2d requires that any application-supplied function or table used by this function must be optional: if the application does not supply it, the square root function must still compute square roots.)

    These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Library, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Library, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

    Thus, it is not the intent of this section to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Library.

    In addition, mere aggregation of another work not based on the Library with the Library (or with a work based on the Library) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.

  4. You may opt to apply the terms of the ordinary GNU General Public License instead of this License to a given copy of the Library. To do this, you must alter all the notices that refer to this License, so that they refer to the ordinary GNU General Public License, version 2, instead of to this License. (If a newer version than version 2 of the ordinary GNU General Public License has appeared, then you can specify that version instead if you wish.) Do not make any other change in these notices.

    Once this change is made in a given copy, it is irreversible for that copy, so the ordinary GNU General Public License applies to all subsequent copies and derivative works made from that copy.

    This option is useful when you wish to copy part of the code of the Library into a program that is not a library.

  5. You may copy and distribute the Library (or a portion or derivative of it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange.

    If distribution of object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place satisfies the requirement to distribute the source code, even though third parties are not compelled to copy the source along with the object code.

  6. A program that contains no derivative of any portion of the Library, but is designed to work with the Library by being compiled or linked with it, is called a "work that uses the Library". Such a work, in isolation, is not a derivative work of the Library, and therefore falls outside the scope of this License.

    However, linking a "work that uses the Library" with the Library creates an executable that is a derivative of the Library (because it contains portions of the Library), rather than a "work that uses the library". The executable is therefore covered by this License. Section 6 states terms for distribution of such executables.

    When a "work that uses the Library" uses material from a header file that is part of the Library, the object code for the work may be a derivative work of the Library even though the source code is not. Whether this is true is especially significant if the work can be linked without the Library, or if the work is itself a library. The threshold for this to be true is not precisely defined by law.

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How to Apply These Terms to Your New Libraries

If you develop a new library, and you want it to be of the greatest possible use to the public, we recommend making it free software that everyone can redistribute and change. You can do so by permitting redistribution under these terms (or, alternatively, under the terms of the ordinary General Public License).

To apply these terms, attach the following notices to the library. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the "copyright" line and a pointer to where the full notice is found. 

     one line to give the library's name and an idea of what it does.
     Copyright (C) year  name of author
     
     This library is free software; you can redistribute it and/or modify it
     under the terms of the GNU Lesser General Public License as published by
     the Free Software Foundation; either version 2.1 of the License, or (at
     your option) any later version.
     
     This library is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Lesser General Public License for more details.
     
     You should have received a copy of the GNU Lesser General Public
     License along with this library; if not, write to the Free Software
     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307,
     USA.

Also add information on how to contact you by electronic and paper mail.

You should also get your employer (if you work as a programmer) or your school, if any, to sign a "copyright disclaimer" for the library, if necessary. Here is a sample; alter the names: 

     Yoyodyne, Inc., hereby disclaims all copyright interest in the library
     `Frob' (a library for tweaking knobs) written by James Random Hacker.
     
     signature of Ty Coon, 1 April 1990
     Ty Coon, President of Vice

That's all there is to it!

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Appendix C DEMO COPYING

This is the common copying notice for all files found in demos/ and docdemos/ (unless stated otherwise in the file itself). They are distributed under the GNU General Public License with a notable exception:

Copyright (C) 1997-2004 Free Software Foundation, Inc.

Authors: See notice in the demo program. If not listed there, these are the authors of the GNU Pascal Compiler.

This demo program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version.

This demo program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this demo program; see the file COPYING. If not, write to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. Top.

As a special exception, if you incorporate even large parts of the code of this demo program into another program with substantially different functionality, this does not cause the other program to be covered by the GNU General Public License. This exception does not however invalidate any other reasons why it might be covered by the GNU General Public License.

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Appendix D Contributors to GNU Pascal.

Jukka Virtanen
invented GNU Pascal in March 1988, implemented the ISO 7185 and most of the ISO 10206 standard, etc.
Dr. Peter Gerwinski
added Borland Pascal related and other extensions to GNU Pascal in summer 1995, ported GPC to EMX, did most of the development of the compiler from 1996 to 2001, created the WWW home page, etc.
Jan-Jaap van der Heijden
ported GPC to DJGPP and to Microsoft Windows 95/NT, added ELF support in spring 1996, solved a lot of configuration and compatibility problems, created the GPC FAQ, etc.
Frank Heckenbach
rewrote and maintains the Run Time System since July 1997, does most of the development of the compiler since July 2001, wrote most of the units, demo programs, scripts and utilities distributed with GPC, wrote many test programs, maintains the GPC To-Do list (see To Do) and the WWW home page, etc.
Waldek Hebisch
made GPC compatible with gcc-3.1.1 and later backend versions, fixed backend problems on various targets and improved the frontend in the areas of structured initializers, qualified identifiers, etc.
Prof. Abimbola A. Olowofoyeku ("The African Chief")
created the original versions of many BP compatibility units in May 1997, contributed code to other units and the Run Time System, helped porting GPC and the units to Cygwin, mingw and MSYS, wrote a number of test programs, contributed a Borland Delphi-compatible SysUtils unit, etc.
Nick Burrett
fixed some bugs and cleaned up GPC in May 1998, etc.
Matthias Klose
integrated GPC into EGCS and Debian GNU/Linux in May 1998, improved the installation process, etc.
Dominik Freche
improved and extended the GPC manual in August - September 1999 and wrote conversion routines for Borland compatible 6 Byte floating point numbers in December 1999.
Alexey Volokhov
improved the performance of GPC's module/unit support in June 1997.
Bill Currie
implemented more Borland extensions into GPC in July 1997.
Nicola Girardi
wrote the GNU Pascal Coding Standards in November 2001, contributed a GPC unit for the svgalib graphics library for some platforms in February 2000, provided some portability enhancements to the RTS.
Eike Lange
wrote an internationalization unit, translated the GNU Pascal Coding Standards into German and worked on the documentation.
Mirsad Todorovac
translated the GPC documentation into Croatian and contributed code to the run time system.
Francisco Javier Fernandez Serrador
translated the GPC documentation into Spanish.
Maurice Lombardi
maintains the DJGPP port of GPC, improved the numerical routines for real and complex numbers and improved and extended the GMP real routines.
Emil Jerabek
improved the numerical routines for real and complex numbers.

Russ Whitaker
updated and maintains the GNU Pascal FAQ. (see FAQ)
Peter N Lewis
added support for Mac Pascal dialect specific features and improved the documentation.

The development of GNU Pascal profits a lot from independent contributions:


Anja Gerwinski
maintains the GPC mailing list, since September 1999.
Berend de Boer
wrote a lot of useful documentation about Extended Pascal in 1995.
Markus Gerwinski
created the drawing showing a Gnu with Blaise Pascal - small (PNG, 1 kB) large (PNG, 10 kB) - and helped to design the WWW home page in October 1996.
Eike Lange
is writing a book about GPC in German since March 2003.
Eike Lange
contributed units to access MySQL, GNU DBM and PostgreSQL databases in August 2000, and a unit (now part of GPC) and tools for internationalization in October - December 2001.
Eike Lange and Nicola Girardi
together contributed a set of GTK units in February - May 2001.
Nicola Girardi
wrote the GNU Pascal Coding Standards in English. Eike Lange translated them to German.
Prof. Phil Nelson
created a bug reporting system for GPC in October 1996.
Robert Höhne
wrote RHIDE, an integrated development environment for GNU compilers running under Dos (DJGPP) and Linux, and added support for GNU Pascal in autumn 1996.
Sven Hilscher
wrote a mostly BP compatible Graph unit for several platforms in December 1996, now part of the GRX library.
Dario Anzani ("Predator Zeta")
contributed documentation about the use of assembler in GNU Pascal in May 1997. (see Assembler)
Dieter Schmitz
set up a German mailing list for GPC, Mailing List, in March 2001.
Adriaan van Os
helped with the port of GPC to Mac OS X and set up a web site with sources, binaries, patches and building instructions for this platform in January 2003.
(-:---------:-)
This space is reserved for your name. ;-) Please contact us at the GPC mailing list, Mailing List, if you have something interesting for us.

We thank everybody who supports us by reporting bugs, providing feedback, contributing knowledge and good ideas, donating development tools, and giving us the opportunity to test GPC on a large variety of systems. We are particularly indebted (in alphabetical order, individuals first) to

Sietse Achterop, Jawaad Ahmad, Montaz Ali, Jamie Allan, Strobe Anarkhos, John P. R. Archer, Phil Armsdon, Geoffrey Arnold, Artur Bac, Steven J. Backus, Geoff Bagley, Andy Ball, Uwe Bauermann, Silvio a Beccara, Michael Behm, Ariel Bendersky, Pablo Bendersky, John Blakeney, Nicolas Bley, Philip Blundell, Preben Mikael Bohn, Ernst-Ludwig Bohnen, Nils Bokermann, Francesco Bonomi, J. Booij, Patrice Bouchand, Jim Brander, Frank Thomas Braun, Matthias Braun, Marcus Brinkmann, Steve Brooker, Doug Brookmann, J. David Bryan, Kev Buckley, Jason Burgon, Ricky W. Butler, Dr. E. Buxbaum, Andrew Cagney, Loris Caren, Theo Carr-Brion, Fernando Carrilho, Larry Carter, Fabio Casamatta, Janet Casey, Romain Chantereau, Emmanuel Chaput, Jean-Pierre Chevillard, Carl Eric Codere, Jean-Philippe Combe, Paolo Cortelli, F. Couperin, Nicolas Courtel, Miklos Cserzo, Tim Currie, Serafim Dahl, Paul Davidson, Martin G. C. Davies, Stefan A. Deutscher, Jerry van Dijk, Thomas Dunbar, Andreas Eckleder, Stephan Eickschen, Frank D. Engel Jr., Sven Engelhardt, Klaus Espenlaub, Toby Ewing, Chuck B. Falconer, Joachim Falk, Irfan Fazel, Carel Fellinger, Francisco Javier Fernandez, Christopher Ferrall, David Fiddes, Alfredo Cesar Fontana, Kevin A. Foss, B. Gayathri, Marius Gedminas, Philip George, Nicholas Geovanis, Jose Oliver Gil, Thorsten Glaser, Jing Gloria, Roland Goretzki, Morten Gulbrandsen, Gerrit P. Haase, Kocherlakota Harikrishna, Joe Hartley, Hans Hauska, Jakob Heinemann, Boris Herman, Arvid Herzenberg, Thorsten Hindermann, Honda Hirotaka, Stephen Hurd, Nick Ioffe, Mason Ip, Fredrik Ismyren, Richard D. Jackson, Daniel Jacobowitz, Grant Jacobs, Andreas Jaeger, Frank Jahnke, David James, Nathalie Jarosz, Sven Jauring, Niels Kristian Bech Jensen, Johanna Johnston, Achim Kalwa, Christine Karow, Tim Kaulmann, Thomas Keller, Clark Kent, Victor Khimenko, Russell King, Niels Ole Staub Kirkeby, Prof. Donald E. Knuth, Michael Kochiashvili, Tomasz Kowaltowski, David Kredba, Peter Ulrich Kruppa, Jochen Kuepper, Casper ter Kuile, Oliver Kullmann, Krzysztof Kwapien, Randy Latimer, Bernard Leak, Olivier Lecarme, Wren Lee, Martin Liddle, Kennith Linder, Stephen Lindholm, Orlando Llanes, Miguel Lobo, Benedict Lofstedt, Steve Loft, John Logsdon, Dominique Louis, Dmitry S. Luhtionov, Jesper Lund, Martin Maechler, Muhammad Umer Mansoor, Claude Marinier, Ingvar Marny, Antony Matranga, Michael McCarthy, Michael Meeks, Clyde Meli, Axel Mellinger, Bryan Meredith, Jeff Miller, John Miller, Russell Minnich, Rudy Moddemeijer, Jason Moore, Scott A. Moore, Jeffrey Moskot, Pierre Muller, Adam Naumowicz, Nathanael Nerode, Andreas Neumann, Christian Neumann, Peter Norton, Adam Oldham, Gerhard Olejniczak, Alexandre Oliva, John G. Ollason, Marius Onica, Ole Osterby, Klaus Friis Ostergaard, Jean-Marc Ottorini, Michael Paap, Gale Paeper, Matija Papec, Miguel A. Alonso Pardo, Laurent Parise, Andris Pavenis, Robert R. Payne, Opie Pecheux, Jose M. Perez, Ronald Perrella, Bjorn Persson, Per Persson, Michael Pfeiffer, Pierre Phaneuf, Pascal Pignard, Tam Pikey, Nuno Pinhao, Philip Plant, Larry Poorman, Stuart Pope, Yuri Prokushev, Huge Rademaker, Shafiek Rasdien, Mike Reid, Leon Renkema, John L. Ries, Phil Robertson, Clive Rodgers, Jim Roland, Guillaume Rousse, Daniel Rudy, Marten Jan de Ruiter, Martin Rusko, Sven Sahle, Neil Santos, Carl-Johan Schenstrom, Robert B. Scher, Hartmut Schmider, Thomas D. Schneider, Dominique Schuppli, Egbert Seibertz, George Shapovalov, Richard Sharman, Patrick Sharp, Joe da Silva, Arcadio Alivio Sincero, Ian Sinclair, Kasper Souren, Tomas Srb, Anuradha Srinivasan, David Starner, Andrew Stribblehill, Alan Sun, Veli Suorsa, Matthew Swift, Mark Taylor, Paul Tedaldi, Robin S. Thompson, Ian Thurlbeck, Gerhard Tonn, Ivan Torshin, Bernhard Tschirren, Josef Urban, Luiz Vaz, Tom Verhoeff, Kresimir Veselic, Jean-Pierre Vial, Alejandro Villarroel, Bohdan Vlasyuk, Marco van de Voort, Raymond Wang, Nic Webb, Peter Weber, Francisco Stefano Wechsler, Christian Wendt, Benedikt Wildenhain, Gareth Wilson, Marc van Woerkom, David Wood, Michael Worsley, Takashi Yamanoue, George L. Yang, Salaam Yitbarek, Dafi Yondra, Eli Zaretskii, Artur Zaroda, Gerhard Zintel, Mariusz Zynel, the BIP at the University of Birmingham, UK, the Institut fuer Festkoerperforschung (IFF) at the Forschungszentrum Juelich, Germany, CARNet (Croatian Academic and Research NETwork), the Academy of Fine Arts and the Faculty of Graphic Arts at the University of Zagreb, Croatia,

and everybody we might have forgotten to mention here. Thanks to all of you!

GNU Pascal is based on GNU CC by Richard Stallman. Several people have contributed to GNU CC:

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Appendix E Resources For Use With GPC.

Many of the programs mentioned here, plus some more, can be found at 

     http://www.gnu-pascal.de/contrib/

[Gnu and Blaise Pascal]
(PNG, 10 KB)

GNU Pascal Drawing

Here is our GNU Pascal drawing as a small (1 KB) and a large PNG image (10 KB), as an EPS file (45 KB), and as a PDF file (18 KB).

Due to patent problems we do not use GIF files. Fortunately the PNG format, the successor of GIF, does not have this problem - and introduces better compression and more advanced features anyway.

By the way, the color gradient that makes our page background is a PNG file of only 632 bytes. It was generated by a Pascal program compiled with GPC and pnmtopng. [Example]

[PENG screen]
(PNG, 7 KB)

PENG

PENG is an integrated development environment (IDE) for GNU Compilers and other purposes on any platform supported by GPC, written by Frank Heckenbach. The home page of PENG is 

     http://fjf.gnu.de/peng/.

[RHIDE screen]
(PNG, 8 KB)

RHIDE

RHIDE is an integrated development environment (IDE) for GNU Compilers on DOS (DJGPP) or Linux, written by Robert Höhne. The home page of RHIDE is 

     http://www.rhide.com.

DevPascal

DevPascal is an integrated development environment (IDE) for GNU Pascal on mingw32. The home page of DevPascal is 

     http://www.bloodshed.net/devpascal.html.

[GRX demo program screen]
(PNG, 38 KB)

GRX

GRX is a graphics library for C and GNU Pascal, including a mostly BP compatible Graph unit. It is available from 

     http://www.gnu.de/software/grx/

Although GRX originated on DJGPP, a DOS programming platform, it is portable to Linux with SVGAlib, to all Unix-like systems running the X11 window system, and to MS-Windows 9x/NT.

Internationalization

Units and tools for internationalization are available in 

     http://www.gnu-pascal.de/contrib/eike/

Database units

GNU Pascal units to access MySQL, GNU DBM and PostgreSQL databases are available in 

     http://www.gnu-pascal.de/contrib/eike/

GTK units

GNU Pascal units for the GTK+ and GTK+ GL libraries are available in 

     http://www.gnu-pascal.de/contrib/nicola/

Documentation

A book about GPC manual in German written by Eike Lange can be found in 

     http://www.gnu-pascal.org/~eike/

SysUtils unit

Prof. Abimbola A. Olowofoyeku ("The African Chief") wrote a Delphi-compatible (though a few routines are still missing) SysUtils unit. It has been tested under Cygwin, mingw, Linux (Mandrake 7.0), and Solaris 7. It can be downloaded from http://www.gnu-pascal.de/contrib/chief/.

Crystal, a mailing list archive program

Crystal is a web based mailing list archive, written for GNU Pascal and used for the archives of GPC's mailing lists (see Mailing List Archives). The source code can be found at http://fjf.gnu.de/crystal/.

ISO standards

The Pascal standard specifications are available in PostScript format at 

     http://ftp.digital.com/pub/Digital/Pascal/

Alternative addresses are 

     ftp://ftp.europe.digital.com/pub/DEC/Pascal/
     
     ftp://ftp.digital.com/pub/DEC/Pascal/

There are also copies at 

     http://www.moorecad.com/standardpascal/iso7185.ps
     (ISO 7185 Pascal)
     
     http://www.moorecad.com/standardpascal/iso10206.ps
     (ISO 10206 Extended Pascal)

Note: These documents are a bit hard to navigate (e.g., in ghostview) because they are missing the so called "document structuring comments" (DSC). The GPC source distribution contains a little script ps2dsc to add the DSC again and make the documents easier to navigate. Note that for reasons of copyright, you are probably only allowed to do this for your own use and not to distribute the modified files.

You can find an easy-to-read introduction to Extended Pascal by Prospero Software at 

     http://www.prosperosoftware.com/epintro.html

Please note that Standard Pascal is not the same as Borland Pascal nor a subset of it. See Highlights for examples of Standard Pascal features that are missing in Borland Pascal.

Scott A. Moore's ANSI-ISO Pascal FAQ (132 KB) discusses the differences between both dialects in detail.

The draft standard "Object-Oriented Extensions to Pascal" can be found at 

     http://pascal-central.com/OOE-stds.html

Software Patents Kill Innovation

Programming activities of small companies and individuals are threatened by software patents. If you are a programmer, you are in danger, too! Your employer or yourself might be sued by a large company holding a patent on some ideas you are using in your programs. (You need not use foreign code in order to become vulnerable.)

For more information look at 

     http://swpat.ffii.org (Europe)
     http://lpf.ai.mit.edu (USA)

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Appendix F The GNU Project.

GNU Pascal is part of the GNU project which was founded by Richard Stallman in 1984. The aim of the GNU project is to provide a complete operating system with editors, compilers etc. as Free Software.

People often confuse Free Software with public domain software or have other wrong information about the GNU project. If you want to know it definitely, please read the GNU General Public License.

For even more information, please consult the official GNU home page of the Free Software Foundation (FSF),

Some small notes about common misunderstandings follow.

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F.1 The GNU Manifesto

The GNU Manifesto which appears below was written by Richard Stallman at the beginning of the GNU project, to ask for participation and support. For the first few years, it was updated in minor ways to account for developments, but now it seems best to leave it unchanged as most people have seen it.

Since that time, we have learned about certain common misunderstandings that different wording could help avoid. Footnotes added in 1993 help clarify these points.

For up-to-date information about the available GNU software, please see the latest issue of the GNU's Bulletin. The list is much too long to include here.

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F.1.1 What's GNU? Gnu's Not Unix!

GNU, which stands for Gnu's Not Unix, is the name for the complete Unix-compatible software system which I am writing so that I can give it away free to everyone who can use it.1 Several other volunteers are helping me. Contributions of time, money, programs and equipment are greatly needed.

So far we have an Emacs text editor with Lisp for writing editor commands, a source level debugger, a yacc-compatible parser generator, a linker, and around 35 utilities. A shell (command interpreter) is nearly completed. A new portable optimizing C compiler has compiled itself and may be released this year. An initial kernel exists but many more features are needed to emulate Unix. When the kernel and compiler are finished, it will be possible to distribute a GNU system suitable for program development. We will use TeX as our text formatter, but an nroff is being worked on. We will use the free, portable X window system as well. After this we will add a portable Common Lisp, an Empire game, a spreadsheet, and hundreds of other things, plus on-line documentation. We hope to supply, eventually, everything useful that normally comes with a Unix system, and more.

GNU will be able to run Unix programs, but will not be identical to Unix. We will make all improvements that are convenient, based on our experience with other operating systems. In particular, we plan to have longer file names, file version numbers, a crashproof file system, file name completion perhaps, terminal-independent display support, and perhaps eventually a Lisp-based window system through which several Lisp programs and ordinary Unix programs can share a screen. Both C and Lisp will be available as system programming languages. We will try to support UUCP, MIT Chaosnet, and Internet protocols for communication.

GNU is aimed initially at machines in the 68000/16000 class with virtual memory, because they are the easiest machines to make it run on. The extra effort to make it run on smaller machines will be left to someone who wants to use it on them.

To avoid horrible confusion, please pronounce the `G' in the word `GNU' when it is the name of this project.

Node: Why GNU, Next: , Previous: Gnu is Not Unix, Up: Manifesto

F.1.2 Why I Must Write GNU

I consider that the golden rule requires that if I like a program I must share it with other people who like it. Software sellers want to divide the users and conquer them, making each user agree not to share with others. I refuse to break solidarity with other users in this way. I cannot in good conscience sign a nondisclosure agreement or a software license agreement. For years I worked within the Artificial Intelligence Lab to resist such tendencies and other inhospitalities, but eventually they had gone too far: I could not remain in an institution where such things are done for me against my will.

So that I can continue to use computers without dishonor, I have decided to put together a sufficient body of free software so that I will be able to get along without any software that is not free. I have resigned from the AI lab to deny MIT any legal excuse to prevent me from giving GNU away.

Node: GNU Unix Compatibility, Next: , Previous: Why GNU, Up: Manifesto

F.1.3 Why GNU Will Be Compatible with Unix

Unix is not my ideal system, but it is not too bad. The essential features of Unix seem to be good ones, and I think I can fill in what Unix lacks without spoiling them. And a system compatible with Unix would be convenient for many other people to adopt.

Node: GNU Availability, Next: , Previous: GNU Unix Compatibility, Up: Manifesto

F.1.4 How GNU Will Be Available

GNU is not in the public domain. Everyone will be permitted to modify and redistribute GNU, but no distributor will be allowed to restrict its further redistribution. That is to say, proprietary modifications will not be allowed. I want to make sure that all versions of GNU remain free.

Node: Why Help GNU, Next: , Previous: GNU Availability, Up: Manifesto

F.1.5 Why Many Other Programmers Want to Help

I have found many other programmers who are excited about GNU and want to help.

Many programmers are unhappy about the commercialization of system software. It may enable them to make more money, but it requires them to feel in conflict with other programmers in general rather than feel as comrades. The fundamental act of friendship among programmers is the sharing of programs; marketing arrangements now typically used essentially forbid programmers to treat others as friends. The purchaser of software must choose between friendship and obeying the law. Naturally, many decide that friendship is more important. But those who believe in law often do not feel at ease with either choice. They become cynical and think that programming is just a way of making money.

By working on and using GNU rather than proprietary programs, we can be hospitable to everyone and obey the law. In addition, GNU serves as an example to inspire and a banner to rally others to join us in sharing. This can give us a feeling of harmony which is impossible if we use software that is not free. For about half the programmers I talk to, this is an important happiness that money cannot replace.

Node: How To Contribute to GNU, Next: , Previous: Why Help GNU, Up: Manifesto

F.1.6 How You Can Contribute

I am asking computer manufacturers for donations of machines and money. I'm asking individuals for donations of programs and work.

One consequence you can expect if you donate machines is that GNU will run on them at an early date. The machines should be complete, ready to use systems, approved for use in a residential area, and not in need of sophisticated cooling or power.

I have found very many programmers eager to contribute part-time work for GNU. For most projects, such part-time distributed work would be very hard to coordinate; the independently-written parts would not work together. But for the particular task of replacing Unix, this problem is absent. A complete Unix system contains hundreds of utility programs, each of which is documented separately. Most interface specifications are fixed by Unix compatibility. If each contributor can write a compatible replacement for a single Unix utility, and make it work properly in place of the original on a Unix system, then these utilities will work right when put together. Even allowing for Murphy to create a few unexpected problems, assembling these components will be a feasible task. (The kernel will require closer communication and will be worked on by a small, tight group.)

If I get donations of money, I may be able to hire a few people full or part time. The salary won't be high by programmers' standards, but I'm looking for people for whom building community spirit is as important as making money. I view this as a way of enabling dedicated people to devote their full energies to working on GNU by sparing them the need to make a living in another way.

Node: GNU Benefits, Next: , Previous: How To Contribute to GNU, Up: Manifesto

F.1.7 Why All Computer Users Will Benefit

Once GNU is written, everyone will be able to obtain good system software free, just like air.2

This means much more than just saving everyone the price of a Unix license. It means that much wasteful duplication of system programming effort will be avoided. This effort can go instead into advancing the state of the art.

Complete system sources will be available to everyone. As a result, a user who needs changes in the system will always be free to make them himself, or hire any available programmer or company to make them for him. Users will no longer be at the mercy of one programmer or company which owns the sources and is in sole position to make changes.

Schools will be able to provide a much more educational environment by encouraging all students to study and improve the system code. Harvard's computer lab used to have the policy that no program could be installed on the system if its sources were not on public display, and upheld it by actually refusing to install certain programs. I was very much inspired by this.

Finally, the overhead of considering who owns the system software and what one is or is not entitled to do with it will be lifted.

Arrangements to make people pay for using a program, including licensing of copies, always incur a tremendous cost to society through the cumbersome mechanisms necessary to figure out how much (that is, which programs) a person must pay for. And only a police state can force everyone to obey them. Consider a space station where air must be manufactured at great cost: charging each breather per liter of air may be fair, but wearing the metered gas mask all day and all night is intolerable even if everyone can afford to pay the air bill. And the TV cameras everywhere to see if you ever take the mask off are outrageous. It's better to support the air plant with a head tax and chuck the masks.

Copying all or parts of a program is as natural to a programmer as breathing, and as productive. It ought to be as free.

Node: Objections to GNU, Previous: GNU Benefits, Up: Manifesto

F.1.8 Some Easily Rebutted Objections to GNU's Goals

"Nobody will use it if it is free, because that means they can't rely on any support."

"You have to charge for the program to pay for providing the support."

If people would rather pay for GNU plus service than get GNU free without service, a company to provide just service to people who have obtained GNU free ought to be profitable.3

We must distinguish between support in the form of real programming work and mere handholding. The former is something one cannot rely on from a software vendor. If your problem is not shared by enough people, the vendor will tell you to get lost.

If your business needs to be able to rely on support, the only way is to have all the necessary sources and tools. Then you can hire any available person to fix your problem; you are not at the mercy of any individual. With Unix, the price of sources puts this out of consideration for most businesses. With GNU this will be easy. It is still possible for there to be no available competent person, but this problem cannot be blamed on distribution arrangements. GNU does not eliminate all the world's problems, only some of them.

Meanwhile, the users who know nothing about computers need handholding: doing things for them which they could easily do themselves but don't know how.

Such services could be provided by companies that sell just hand-holding and repair service. If it is true that users would rather spend money and get a product with service, they will also be willing to buy the service having got the product free. The service companies will compete in quality and price; users will not be tied to any particular one. Meanwhile, those of us who don't need the service should be able to use the program without paying for the service.

"You cannot reach many people without advertising, and you must charge for the program to support that."

"It's no use advertising a program people can get free."

There are various forms of free or very cheap publicity that can be used to inform numbers of computer users about something like GNU. But it may be true that one can reach more microcomputer users with advertising. If this is really so, a business which advertises the service of copying and mailing GNU for a fee ought to be successful enough to pay for its advertising and more. This way, only the users who benefit from the advertising pay for it.

On the other hand, if many people get GNU from their friends, and such companies don't succeed, this will show that advertising was not really necessary to spread GNU. Why is it that free market advocates don't want to let the free market decide this?4

"My company needs a proprietary operating system to get a competitive edge."

GNU will remove operating system software from the realm of competition. You will not be able to get an edge in this area, but neither will your competitors be able to get an edge over you. You and they will compete in other areas, while benefiting mutually in this one. If your business is selling an operating system, you will not like GNU, but that's tough on you. If your business is something else, GNU can save you from being pushed into the expensive business of selling operating systems.

I would like to see GNU development supported by gifts from many manufacturers and users, reducing the cost to each.5

"Don't programmers deserve a reward for their creativity?"

If anything deserves a reward, it is social contribution. Creativity can be a social contribution, but only in so far as society is free to use the results. If programmers deserve to be rewarded for creating innovative programs, by the same token they deserve to be punished if they restrict the use of these programs.

"Shouldn't a programmer be able to ask for a reward for his creativity?"

There is nothing wrong with wanting pay for work, or seeking to maximize one's income, as long as one does not use means that are destructive. But the means customary in the field of software today are based on destruction.

Extracting money from users of a program by restricting their use of it is destructive because the restrictions reduce the amount and the ways that the program can be used. This reduces the amount of wealth that humanity derives from the program. When there is a deliberate choice to restrict, the harmful consequences are deliberate destruction.

The reason a good citizen does not use such destructive means to become wealthier is that, if everyone did so, we would all become poorer from the mutual destructiveness. This is Kantian ethics; or, the Golden Rule. Since I do not like the consequences that result if everyone hoards information, I am required to consider it wrong for one to do so. Specifically, the desire to be rewarded for one's creativity does not justify depriving the world in general of all or part of that creativity.

"Won't programmers starve?"

I could answer that nobody is forced to be a programmer. Most of us cannot manage to get any money for standing on the street and making faces. But we are not, as a result, condemned to spend our lives standing on the street making faces, and starving. We do something else.

But that is the wrong answer because it accepts the questioner's implicit assumption: that without ownership of software, programmers cannot possibly be paid a cent. Supposedly it is all or nothing.

The real reason programmers will not starve is that it will still be possible for them to get paid for programming; just not paid as much as now.

Restricting copying is not the only basis for business in software. It is the most common basis because it brings in the most money. If it were prohibited, or rejected by the customer, software business would move to other bases of organization which are now used less often. There are always numerous ways to organize any kind of business.

Probably programming will not be as lucrative on the new basis as it is now. But that is not an argument against the change. It is not considered an injustice that sales clerks make the salaries that they now do. If programmers made the same, that would not be an injustice either. (In practice they would still make considerably more than that.)

"Don't people have a right to control how their creativity is used?"

"Control over the use of one's ideas" really constitutes control over other people's lives; and it is usually used to make their lives more difficult.

People who have studied the issue of intellectual property rights carefully (such as lawyers) say that there is no intrinsic right to intellectual property. The kinds of supposed intellectual property rights that the government recognizes were created by specific acts of legislation for specific purposes.

For example, the patent system was established to encourage inventors to disclose the details of their inventions. Its purpose was to help society rather than to help inventors. At the time, the life span of 17 years for a patent was short compared with the rate of advance of the state of the art. Since patents are an issue only among manufacturers, for whom the cost and effort of a license agreement are small compared with setting up production, the patents often do not do much harm. They do not obstruct most individuals who use patented products.

The idea of copyright did not exist in ancient times, when authors frequently copied other authors at length in works of non-fiction. This practice was useful, and is the only way many authors' works have survived even in part. The copyright system was created expressly for the purpose of encouraging authorship. In the domain for which it was invented - books, which could be copied economically only on a printing press - it did little harm, and did not obstruct most of the individuals who read the books.

All intellectual property rights are just licenses granted by society because it was thought, rightly or wrongly, that society as a whole would benefit by granting them. But in any particular situation, we have to ask: are we really better off granting such license? What kind of act are we licensing a person to do?

The case of programs today is very different from that of books a hundred years ago. The fact that the easiest way to copy a program is from one neighbor to another, the fact that a program has both source code and object code which are distinct, and the fact that a program is used rather than read and enjoyed, combine to create a situation in which a person who enforces a copyright is harming society as a whole both materially and spiritually; in which a person should not do so regardless of whether the law enables him to.

"Competition makes things get done better."

The paradigm of competition is a race: by rewarding the winner, we encourage everyone to run faster. When capitalism really works this way, it does a good job; but its defenders are wrong in assuming it always works this way. If the runners forget why the reward is offered and become intent on winning, no matter how, they may find other strategies - such as, attacking other runners. If the runners get into a fist fight, they will all finish late.

Proprietary and secret software is the moral equivalent of runners in a fist fight. Sad to say, the only referee we've got does not seem to object to fights; he just regulates them ("For every ten yards you run, you can fire one shot"). He really ought to break them up, and penalize runners for even trying to fight.

"Won't everyone stop programming without a monetary incentive?"

Actually, many people will program with absolutely no monetary incentive. Programming has an irresistible fascination for some people, usually the people who are best at it. There is no shortage of professional musicians who keep at it even though they have no hope of making a living that way.

But really this question, though commonly asked, is not appropriate to the situation. Pay for programmers will not disappear, only become less. So the right question is, will anyone program with a reduced monetary incentive? My experience shows that they will.

For more than ten years, many of the world's best programmers worked at the Artificial Intelligence Lab for far less money than they could have had anywhere else. They got many kinds of non-monetary rewards: fame and appreciation, for example. And creativity is also fun, a reward in itself.

Then most of them left when offered a chance to do the same interesting work for a lot of money.

What the facts show is that people will program for reasons other than riches; but if given a chance to make a lot of money as well, they will come to expect and demand it. Low-paying organizations do poorly in competition with high-paying ones, but they do not have to do badly if the high-paying ones are banned.

"We need the programmers desperately. If they demand that we stop helping our neighbors, we have to obey."

You're never so desperate that you have to obey this sort of demand. Remember: millions for defense, but not a cent for tribute!

"Programmers need to make a living somehow."

In the short run, this is true. However, there are plenty of ways that programmers could make a living without selling the right to use a program. This way is customary now because it brings programmers and businessmen the most money, not because it is the only way to make a living. It is easy to find other ways if you want to find them. Here are a number of examples.

A manufacturer introducing a new computer will pay for the porting of operating systems onto the new hardware.

The sale of teaching, hand-holding and maintenance services could also employ programmers.

People with new ideas could distribute programs as freeware, asking for donations from satisfied users, or selling hand-holding services. I have met people who are already working this way successfully.

Users with related needs can form users' groups, and pay dues. A group would contract with programming companies to write programs that the group's members would like to use.

All sorts of development can be funded with a Software Tax:

Suppose everyone who buys a computer has to pay x percent of the price as a software tax. The government gives this to an agency like the NSF to spend on software development.

But if the computer buyer makes a donation to software development himself, he can take a credit against the tax. He can donate to the project of his own choosing - often, chosen because he hopes to use the results when it is done. He can take a credit for any amount of donation up to the total tax he had to pay.

The total tax rate could be decided by a vote of the payers of the tax, weighted according to the amount they will be taxed on.

The consequences:

In the long run, making programs free is a step toward the post-scarcity world, where nobody will have to work very hard just to make a living. People will be free to devote themselves to activities that are fun, such as programming, after spending the necessary ten hours a week on required tasks such as legislation, family counseling, robot repair and asteroid prospecting. There will be no need to be able to make a living from programming.

We have already greatly reduced the amount of work that the whole society must do for its actual productivity, but only a little of this has translated itself into leisure for workers because much nonproductive activity is required to accompany productive activity. The main causes of this are bureaucracy and isometric struggles against competition. Free software will greatly reduce these drains in the area of software production. We must do this, in order for technical gains in productivity to translate into less work for us.

Node: Funding, Previous: Manifesto, Up: GNU

F.2 Funding Free Software

If you want to have more free software a few years from now, it makes sense for you to help encourage people to contribute funds for its development. The most effective approach known is to encourage commercial redistributors to donate.

Users of free software systems can boost the pace of development by encouraging for-a-fee distributors to donate part of their selling price to free software developers - the Free Software Foundation, and others.

The way to convince distributors to do this is to demand it and expect it from them. So when you compare distributors, judge them partly by how much they give to free software development. Show distributors they must compete to be the one who gives the most.

To make this approach work, you must insist on numbers that you can compare, such as, "We will donate ten dollars to the Frobnitz project for each disk sold." Don't be satisfied with a vague promise, such as "A portion of the profits are donated," since it doesn't give a basis for comparison.

Even a precise fraction "of the profits from this disk" is not very meaningful, since creative accounting and unrelated business decisions can greatly alter what fraction of the sales price counts as profit. If the price you pay is $50, ten percent of the profit is probably less than a dollar; it might be a few cents, or nothing at all.

Some redistributors do development work themselves. This is useful too; but to keep everyone honest, you need to inquire how much they do, and what kind. Some kinds of development make much more long-term difference than others. For example, maintaining a separate version of a program contributes very little; maintaining the standard version of a program for the whole community contributes much. Easy new ports contribute little, since someone else would surely do them; difficult ports such as adding a new CPU to the GNU C compiler contribute more; major new features or packages contribute the most.

By establishing the idea that supporting further development is "the proper thing to do" when distributing free software for a fee, we can assure a steady flow of resources into making more free software. 

     Copyright (C) 1994 Free Software Foundation, Inc.
     Verbatim copying and redistribution of this section is permitted
     without royalty; alteration is not permitted.

Node: Index-GPC, Previous: GNU, Up: Top

Index-GPC

Footnotes

  1. The wording here was careless. The intention was that nobody would have to pay for permission to use the GNU system. But the words don't make this clear, and people often interpret them as saying that copies of GNU should always be distributed at little or no charge. That was never the intent; later on, the manifesto mentions the possibility of companies providing the service of distribution for a profit. Subsequently I have learned to distinguish carefully between "free" in the sense of freedom and "free" in the sense of price. Free software is software that users have the freedom to distribute and change. Some users may obtain copies at no charge, while others pay to obtain copies - and if the funds help support improving the software, so much the better. The important thing is that everyone who has a copy has the freedom to cooperate with others in using it.

  2. This is another place I failed to distinguish carefully between the two different meanings of "free". The statement as it stands is not false - you can get copies of GNU software at no charge, from your friends or over the net. But it does suggest the wrong idea.

  3. Several such companies now exist.

  4. The Free Software Foundation raises most of its funds from a distribution service, although it is a charity rather than a company. If no one chooses to obtain copies by ordering from the FSF, it will be unable to do its work. But this does not mean that proprietary restrictions are justified to force every user to pay. If a small fraction of all the users order copies from the FSF, that is sufficient to keep the FSF afloat. So we ask users to choose to support us in this way. Have you done your part?

  5. A group of computer companies recently pooled funds to support maintenance of the GNU C Compiler.