tr1/tuple

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00001 // class template tuple -*- C++ -*-
00002 
00003 // Copyright (C) 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
00004 //
00005 // This file is part of the GNU ISO C++ Library.  This library is free
00006 // software; you can redistribute it and/or modify it under the
00007 // terms of the GNU General Public License as published by the
00008 // Free Software Foundation; either version 2, or (at your option)
00009 // any later version.
00010 
00011 // This library is distributed in the hope that it will be useful,
00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014 // GNU General Public License for more details.
00015 
00016 // You should have received a copy of the GNU General Public License along
00017 // with this library; see the file COPYING.  If not, write to the Free
00018 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
00019 // USA.
00020 
00021 // As a special exception, you may use this file as part of a free software
00022 // library without restriction.  Specifically, if other files instantiate
00023 // templates or use macros or inline functions from this file, or you compile
00024 // this file and link it with other files to produce an executable, this
00025 // file does not by itself cause the resulting executable to be covered by
00026 // the GNU General Public License.  This exception does not however
00027 // invalidate any other reasons why the executable file might be covered by
00028 // the GNU General Public License.
00029 
00030 /** @file tr1/tuple
00031 *  This is a TR1 C++ Library header.
00032 */
00033 
00034 // Chris Jefferson <chris@bubblescope.net>
00035 // Variadic Templates support by Douglas Gregor <doug.gregor@gmail.com>
00036 
00037 #ifndef _GLIBCXX_TR1_TUPLE
00038 #define _GLIBCXX_TR1_TUPLE 1
00039 
00040 #pragma GCC system_header
00041 
00042 #include <utility>
00043 
00044 namespace std
00045 {
00046 namespace tr1
00047 {
00048   // Adds a const reference to a non-reference type.
00049   template<typename _Tp>
00050     struct __add_c_ref
00051     { typedef const _Tp& type; };
00052 
00053   template<typename _Tp>
00054     struct __add_c_ref<_Tp&>
00055     { typedef _Tp& type; };
00056 
00057   // Adds a reference to a non-reference type.
00058   template<typename _Tp>
00059     struct __add_ref
00060     { typedef _Tp& type; };
00061 
00062   template<typename _Tp>
00063     struct __add_ref<_Tp&>
00064     { typedef _Tp& type; };
00065 
00066   /**
00067    * Contains the actual implementation of the @c tuple template, stored
00068    * as a recursive inheritance hierarchy from the first element (most
00069    * derived class) to the last (least derived class). The @c Idx
00070    * parameter gives the 0-based index of the element stored at this
00071    * point in the hierarchy; we use it to implement a constant-time
00072    * get() operation.
00073    */
00074   template<int _Idx, typename... _Elements>
00075     struct _Tuple_impl; 
00076 
00077   /**
00078    * Zero-element tuple implementation. This is the basis case for the 
00079    * inheritance recursion.
00080    */
00081   template<int _Idx>
00082     struct _Tuple_impl<_Idx> { };
00083 
00084   /**
00085    * Recursive tuple implementation. Here we store the @c Head element
00086    * and derive from a @c Tuple_impl containing the remaining elements
00087    * (which contains the @c Tail).
00088    */
00089   template<int _Idx, typename _Head, typename... _Tail>
00090     struct _Tuple_impl<_Idx, _Head, _Tail...>
00091     : public _Tuple_impl<_Idx + 1, _Tail...>
00092     {
00093       typedef _Tuple_impl<_Idx + 1, _Tail...> _Inherited;
00094       
00095       _Head _M_head;
00096       
00097       _Inherited&       _M_tail()       { return *this; }
00098       const _Inherited& _M_tail() const { return *this; }
00099       
00100       _Tuple_impl() : _Inherited(), _M_head() { }
00101       
00102       explicit 
00103       _Tuple_impl(typename __add_c_ref<_Head>::type __head,
00104           typename __add_c_ref<_Tail>::type... __tail)
00105       : _Inherited(__tail...), _M_head(__head) { }
00106 
00107       template<typename... _UElements>
00108       _Tuple_impl(const _Tuple_impl<_Idx, _UElements...>& __in)
00109       : _Inherited(__in._M_tail()), _M_head(__in._M_head) { }
00110 
00111       _Tuple_impl(const _Tuple_impl& __in)
00112       : _Inherited(__in._M_tail()), _M_head(__in._M_head) { }
00113      
00114       template<typename... _UElements>
00115         _Tuple_impl&
00116         operator=(const _Tuple_impl<_Idx, _UElements...>& __in)
00117         {
00118       _M_head = __in._M_head;
00119       _M_tail() = __in._M_tail();
00120       return *this;
00121     }
00122 
00123       _Tuple_impl&
00124       operator=(const _Tuple_impl& __in)
00125       {
00126     _M_head = __in._M_head;
00127     _M_tail() = __in._M_tail();
00128     return *this;
00129       }
00130     };
00131 
00132   template<typename... _Elements> 
00133     class tuple : public _Tuple_impl<0, _Elements...>
00134     {
00135       typedef _Tuple_impl<0, _Elements...> _Inherited;
00136 
00137     public:
00138       tuple() : _Inherited() { }
00139 
00140       explicit
00141       tuple(typename __add_c_ref<_Elements>::type... __elements)
00142       : _Inherited(__elements...) { }
00143 
00144       template<typename... _UElements>
00145         tuple(const tuple<_UElements...>& __in)
00146     : _Inherited(__in) { }
00147 
00148       tuple(const tuple& __in)
00149       : _Inherited(__in) { }
00150 
00151       template<typename... _UElements>
00152         tuple&
00153         operator=(const tuple<_UElements...>& __in)
00154         {
00155       static_cast<_Inherited&>(*this) = __in;
00156       return *this;
00157     }
00158 
00159       tuple&
00160       operator=(const tuple& __in)
00161       {
00162     static_cast<_Inherited&>(*this) = __in;
00163     return *this;
00164       }
00165     };
00166 
00167   template<> class tuple<> { };
00168 
00169   // 2-element tuple, with construction and assignment from a pair.
00170   template<typename _T1, typename _T2>
00171     class tuple<_T1, _T2> : public _Tuple_impl<0, _T1, _T2>
00172     {
00173       typedef _Tuple_impl<0, _T1, _T2> _Inherited;
00174 
00175     public:
00176       tuple() : _Inherited() { }
00177 
00178       explicit
00179       tuple(typename __add_c_ref<_T1>::type __a1,
00180         typename __add_c_ref<_T2>::type __a2)
00181       : _Inherited(__a1, __a2) { }
00182 
00183       template<typename _U1, typename _U2>
00184         tuple(const tuple<_U1, _U2>& __in)
00185     : _Inherited(__in) { }
00186 
00187       tuple(const tuple& __in)
00188       : _Inherited(__in) { }
00189 
00190       template<typename _U1, typename _U2>
00191         tuple(const pair<_U1, _U2>& __in)
00192     : _Inherited(_Tuple_impl<0, 
00193              typename __add_c_ref<_U1>::type,
00194              typename __add_c_ref<_U2>::type>(__in.first, 
00195                               __in.second))
00196         { }
00197   
00198       template<typename _U1, typename _U2>
00199         tuple&
00200         operator=(const tuple<_U1, _U2>& __in)
00201         {
00202       static_cast<_Inherited&>(*this) = __in;
00203       return *this;
00204     }
00205 
00206       tuple&
00207       operator=(const tuple& __in)
00208       {
00209     static_cast<_Inherited&>(*this) = __in;
00210     return *this;
00211       }
00212 
00213       template<typename _U1, typename _U2>
00214         tuple&
00215         operator=(const pair<_U1, _U2>& __in)
00216         {
00217       this->_M_head = __in.first;
00218       this->_M_tail()._M_head = __in.second;
00219       return *this;
00220     }
00221     };
00222 
00223   
00224   /// Gives the type of the ith element of a given tuple type.
00225   template<int __i, typename _Tp>
00226     struct tuple_element;
00227 
00228   /**
00229    * Recursive case for tuple_element: strip off the first element in
00230    * the tuple and retrieve the (i-1)th element of the remaining tuple.
00231    */
00232   template<int __i, typename _Head, typename... _Tail>
00233     struct tuple_element<__i, tuple<_Head, _Tail...> >
00234     : tuple_element<__i - 1, tuple<_Tail...> > { };
00235 
00236   /**
00237    * Basis case for tuple_element: The first element is the one we're seeking.
00238    */
00239   template<typename _Head, typename... _Tail>
00240     struct tuple_element<0, tuple<_Head, _Tail...> >
00241     {
00242       typedef _Head type;
00243     };
00244 
00245   /// Finds the size of a given tuple type.
00246   template<typename _Tp>
00247     struct tuple_size;
00248 
00249   /// class tuple_size
00250   template<typename... _Elements>
00251     struct tuple_size<tuple<_Elements...> >
00252     {
00253       static const int value = sizeof...(_Elements);
00254     };
00255 
00256   template<typename... _Elements>
00257     const int tuple_size<tuple<_Elements...> >::value;
00258 
00259   template<int __i, typename _Head, typename... _Tail>
00260     inline typename __add_ref<_Head>::type
00261     __get_helper(_Tuple_impl<__i, _Head, _Tail...>& __t)
00262     {
00263       return __t._M_head;
00264     }
00265 
00266   template<int __i, typename _Head, typename... _Tail>
00267     inline typename __add_c_ref<_Head>::type
00268     __get_helper(const _Tuple_impl<__i, _Head, _Tail...>& __t)
00269     {
00270       return __t._M_head;
00271     }
00272 
00273   // Return a reference (const reference) to the ith element of a tuple.
00274   // Any const or non-const ref elements are returned with their original type.
00275   template<int __i, typename... _Elements>
00276     inline typename __add_ref<
00277                       typename tuple_element<__i, tuple<_Elements...> >::type
00278                     >::type
00279     get(tuple<_Elements...>& __t)
00280     { 
00281       return __get_helper<__i>(__t); 
00282     }
00283 
00284   template<int __i, typename... _Elements>
00285     inline typename __add_c_ref<
00286                       typename tuple_element<__i, tuple<_Elements...> >::type
00287                     >::type
00288     get(const tuple<_Elements...>& __t)
00289     {
00290       return __get_helper<__i>(__t);
00291     }
00292 
00293   // This class helps construct the various comparison operations on tuples
00294   template<int __check_equal_size, int __i, int __j,
00295        typename _Tp, typename _Up>
00296     struct __tuple_compare;
00297 
00298   template<int __i, int __j, typename _Tp, typename _Up>
00299     struct __tuple_compare<0, __i, __j, _Tp, _Up>
00300     {
00301       static bool __eq(const _Tp& __t, const _Up& __u)
00302       {
00303     return (get<__i>(__t) == get<__i>(__u) &&
00304         __tuple_compare<0, __i+1, __j, _Tp, _Up>::__eq(__t, __u));
00305       }
00306      
00307       static bool __less(const _Tp& __t, const _Up& __u)
00308       {
00309     return ((get<__i>(__t) < get<__i>(__u))
00310         || !(get<__i>(__u) < get<__i>(__t)) &&
00311         __tuple_compare<0, __i+1, __j, _Tp, _Up>::__less(__t, __u));
00312       }
00313     };
00314 
00315   template<int __i, typename _Tp, typename _Up>
00316     struct __tuple_compare<0, __i, __i, _Tp, _Up>
00317     {
00318       static bool __eq(const _Tp&, const _Up&)
00319       { return true; }
00320      
00321       static bool __less(const _Tp&, const _Up&)
00322       { return false; }
00323     };
00324 
00325   template<typename... _TElements, typename... _UElements>
00326     bool
00327     operator==(const tuple<_TElements...>& __t,
00328            const tuple<_UElements...>& __u)
00329     {
00330       typedef tuple<_TElements...> _Tp;
00331       typedef tuple<_UElements...> _Up;
00332       return (__tuple_compare<tuple_size<_Tp>::value - tuple_size<_Up>::value,
00333           0, tuple_size<_Tp>::value, _Tp, _Up>::__eq(__t, __u));
00334     }
00335 
00336   template<typename... _TElements, typename... _UElements>
00337     bool
00338     operator<(const tuple<_TElements...>& __t,
00339           const tuple<_UElements...>& __u)
00340     {
00341       typedef tuple<_TElements...> _Tp;
00342       typedef tuple<_UElements...> _Up;
00343       return (__tuple_compare<tuple_size<_Tp>::value - tuple_size<_Up>::value,
00344           0, tuple_size<_Tp>::value, _Tp, _Up>::__less(__t, __u));
00345     }
00346 
00347   template<typename... _TElements, typename... _UElements>
00348     inline bool
00349     operator!=(const tuple<_TElements...>& __t,
00350            const tuple<_UElements...>& __u)
00351     { return !(__t == __u); }
00352 
00353   template<typename... _TElements, typename... _UElements>
00354     inline bool
00355     operator>(const tuple<_TElements...>& __t,
00356           const tuple<_UElements...>& __u)
00357     { return __u < __t; }
00358 
00359   template<typename... _TElements, typename... _UElements>
00360     inline bool
00361     operator<=(const tuple<_TElements...>& __t,
00362            const tuple<_UElements...>& __u)
00363     { return !(__u < __t); }
00364 
00365   template<typename... _TElements, typename... _UElements>
00366     inline bool
00367     operator>=(const tuple<_TElements...>& __t,
00368            const tuple<_UElements...>& __u)
00369     { return !(__t < __u); }
00370 
00371   template<typename _Tp>
00372     class reference_wrapper;
00373 
00374   // Helper which adds a reference to a type when given a reference_wrapper
00375   template<typename _Tp>
00376     struct __strip_reference_wrapper
00377     {
00378       typedef _Tp __type;
00379     };
00380 
00381   template<typename _Tp>
00382     struct __strip_reference_wrapper<reference_wrapper<_Tp> >
00383     {
00384       typedef _Tp& __type;
00385     };
00386 
00387   template<typename _Tp>
00388     struct __strip_reference_wrapper<const reference_wrapper<_Tp> >
00389     {
00390       typedef _Tp& __type;
00391     };
00392 
00393   template<typename... _Elements>
00394     inline tuple<typename __strip_reference_wrapper<_Elements>::__type...>
00395     make_tuple(_Elements... __args)
00396     {
00397       typedef tuple<typename __strip_reference_wrapper<_Elements>::__type...>
00398         __result_type;
00399       return __result_type(__args...);
00400     }
00401 
00402   template<typename... _Elements>
00403     inline tuple<_Elements&...>
00404     tie(_Elements&... __args)
00405     {
00406       return tuple<_Elements&...>(__args...);
00407     }
00408 
00409   // A class (and instance) which can be used in 'tie' when an element
00410   // of a tuple is not required
00411   struct _Swallow_assign
00412   {
00413     template<class _Tp>
00414       _Swallow_assign&
00415       operator=(const _Tp&)
00416       { return *this; }
00417   };
00418 
00419   // TODO: Put this in some kind of shared file.
00420   namespace
00421   {
00422     _Swallow_assign ignore;
00423   }; // anonymous namespace
00424 }
00425 }
00426 
00427 #endif // _GLIBCXX_TR1_TUPLE

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