net.sf.saxon.query

Class UnboundFunctionLibrary

Implemented Interfaces:
FunctionLibrary, Serializable

public class UnboundFunctionLibrary
extends java.lang.Object
implements FunctionLibrary

An UnboundFunctionLibrary is not a real function library; rather, it is used to keep track of function calls that cannot yet be bound to a known declared function, but will have to be bound when all user-declared functions are available.

Constructor Summary

UnboundFunctionLibrary()
Create an XQueryFunctionLibrary

Method Summary

Expression
bind(StructuredQName functionName, Expression[] arguments, StaticContext env)
Identify a (namespace-prefixed) function appearing in the expression.
void
bindUnboundFunctionCalls(XQueryFunctionBinder lib, Configuration config)
Bind function calls that could not be bound when first encountered.
FunctionLibrary
copy()
This method creates a copy of a FunctionLibrary: if the original FunctionLibrary allows new functions to be added, then additions to this copy will not affect the original, or vice versa.
boolean
isAvailable(StructuredQName functionName, int arity)
Test whether a function with a given name and arity is available.

Constructor Details

UnboundFunctionLibrary

public UnboundFunctionLibrary()
Create an XQueryFunctionLibrary

Method Details

bind

public Expression bind(StructuredQName functionName,
                       Expression[] arguments,
                       StaticContext env)
            throws XPathException
Identify a (namespace-prefixed) function appearing in the expression. This method is called by the XQuery parser to resolve function calls found within the query.

Note that a function call may appear earlier in the query than the definition of the function to which it is bound. Unlike XSLT, we cannot search forwards to find the function definition. Binding of function calls is therefore a two-stage process; at the time the function call is parsed, we simply register it as pending; subsequently at the end of query parsing all the pending function calls are resolved. Another consequence of this is that we cannot tell at the time a function call is parsed whether it is a call to an internal (XSLT or XQuery) function or to an extension function written in Java.

Specified by:
bind in interface FunctionLibrary
Returns:
an Expression representing the function call. This will normally be a FunctionCall, but it may be rewritten as some other expression.
Throws:
XPathException - if the function call is invalid, either because it is an unprefixed call to a non-system function, or because it is calling a system function that is available in XSLT only. A prefixed function call that cannot be recognized at this stage is assumed to be a forwards reference, and is bound later when bindUnboundFunctionCalls() is called.

bindUnboundFunctionCalls

public void bindUnboundFunctionCalls(XQueryFunctionBinder lib,
                                     Configuration config)
            throws XPathException
Bind function calls that could not be bound when first encountered. These will either be forwards references to functions declared later in the query, or errors. This method is for internal use.
Parameters:
lib - A library containing all the XQuery functions that have been declared; the method searches this library for this missing function call
config - The Saxon configuration
Throws:
XPathException - if a function call refers to a function that has not been declared

copy

public FunctionLibrary copy()
This method creates a copy of a FunctionLibrary: if the original FunctionLibrary allows new functions to be added, then additions to this copy will not affect the original, or vice versa.
Specified by:
copy in interface FunctionLibrary
Returns:
a copy of this function library. This must be an instance of the original class.

isAvailable

public boolean isAvailable(StructuredQName functionName,
                           int arity)
Test whether a function with a given name and arity is available. This supports the function-available() function in XSLT. Since this library is used only in XQuery, and contains no real functions, we always return false
Specified by:
isAvailable in interface FunctionLibrary
Parameters:
functionName - the name of the function required
arity - The number of arguments. This is set to -1 in the case of the single-argument function-available() function; in this case the method should return true if there is some