stl_pair.h

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00001 // Pair implementation -*- C++ -*-
00002 
00003 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
00004 // Free Software Foundation, Inc.
00005 //
00006 // This file is part of the GNU ISO C++ Library.  This library is free
00007 // software; you can redistribute it and/or modify it under the
00008 // terms of the GNU General Public License as published by the
00009 // Free Software Foundation; either version 3, or (at your option)
00010 // any later version.
00011 
00012 // This library is distributed in the hope that it will be useful,
00013 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00014 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015 // GNU General Public License for more details.
00016 
00017 // Under Section 7 of GPL version 3, you are granted additional
00018 // permissions described in the GCC Runtime Library Exception, version
00019 // 3.1, as published by the Free Software Foundation.
00020 
00021 // You should have received a copy of the GNU General Public License and
00022 // a copy of the GCC Runtime Library Exception along with this program;
00023 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00024 // <http://www.gnu.org/licenses/>.
00025 
00026 /*
00027  *
00028  * Copyright (c) 1994
00029  * Hewlett-Packard Company
00030  *
00031  * Permission to use, copy, modify, distribute and sell this software
00032  * and its documentation for any purpose is hereby granted without fee,
00033  * provided that the above copyright notice appear in all copies and
00034  * that both that copyright notice and this permission notice appear
00035  * in supporting documentation.  Hewlett-Packard Company makes no
00036  * representations about the suitability of this software for any
00037  * purpose.  It is provided "as is" without express or implied warranty.
00038  *
00039  *
00040  * Copyright (c) 1996,1997
00041  * Silicon Graphics Computer Systems, Inc.
00042  *
00043  * Permission to use, copy, modify, distribute and sell this software
00044  * and its documentation for any purpose is hereby granted without fee,
00045  * provided that the above copyright notice appear in all copies and
00046  * that both that copyright notice and this permission notice appear
00047  * in supporting documentation.  Silicon Graphics makes no
00048  * representations about the suitability of this software for any
00049  * purpose.  It is provided "as is" without express or implied warranty.
00050  */
00051 
00052 /** @file stl_pair.h
00053  *  This is an internal header file, included by other library headers.
00054  *  You should not attempt to use it directly.
00055  */
00056 
00057 #ifndef _STL_PAIR_H
00058 #define _STL_PAIR_H 1
00059 
00060 #include <bits/move.h> // for std::move / std::forward, std::decay, and
00061                        // std::swap
00062 
00063 #ifdef __GXX_EXPERIMENTAL_CXX0X__
00064 #include <type_traits>
00065 #endif
00066 
00067 _GLIBCXX_BEGIN_NAMESPACE(std)
00068 
00069   /// pair holds two objects of arbitrary type.
00070   template<class _T1, class _T2>
00071     struct pair
00072     {
00073       typedef _T1 first_type;    ///<  @c first_type is the first bound type
00074       typedef _T2 second_type;   ///<  @c second_type is the second bound type
00075 
00076       _T1 first;                 ///< @c first is a copy of the first object
00077       _T2 second;                ///< @c second is a copy of the second object
00078 
00079       // _GLIBCXX_RESOLVE_LIB_DEFECTS
00080       // 265.  std::pair::pair() effects overly restrictive
00081       /** The default constructor creates @c first and @c second using their
00082        *  respective default constructors.  */
00083       pair()
00084       : first(), second() { }
00085 
00086       /** Two objects may be passed to a @c pair constructor to be copied.  */
00087       pair(const _T1& __a, const _T2& __b)
00088       : first(__a), second(__b) { }
00089 
00090 #ifdef __GXX_EXPERIMENTAL_CXX0X__
00091       // DR 811.
00092       template<class _U1, class = typename
00093            std::enable_if<std::is_convertible<_U1, _T1>::value>::type>
00094         pair(_U1&& __x, const _T2& __y)
00095     : first(std::forward<_U1>(__x)),
00096       second(__y) { }
00097 
00098       template<class _U2, class = typename
00099            std::enable_if<std::is_convertible<_U2, _T2>::value>::type>
00100         pair(const _T1& __x, _U2&& __y)
00101     : first(__x),
00102       second(std::forward<_U2>(__y)) { }
00103 
00104       template<class _U1, class _U2, class = typename
00105            std::enable_if<std::is_convertible<_U1, _T1>::value
00106                   && std::is_convertible<_U2, _T2>::value>::type>
00107         pair(_U1&& __x, _U2&& __y)
00108     : first(std::forward<_U1>(__x)),
00109       second(std::forward<_U2>(__y)) { }
00110 #endif
00111 
00112       /** There is also a templated copy ctor for the @c pair class itself.  */
00113       template<class _U1, class _U2>
00114         pair(const pair<_U1, _U2>& __p)
00115     : first(__p.first),
00116       second(__p.second) { }
00117 
00118 #ifdef __GXX_EXPERIMENTAL_CXX0X__
00119       template<class _U1, class _U2>
00120         pair(pair<_U1, _U2>&& __p)
00121     : first(std::forward<_U1>(__p.first)),
00122       second(std::forward<_U2>(__p.second)) { }
00123 
00124       pair&
00125       operator=(pair&& __p)
00126       { 
00127     first = std::move(__p.first);
00128     second = std::move(__p.second);
00129     return *this;
00130       }
00131 
00132       template<class _U1, class _U2>
00133         pair&
00134         operator=(pair<_U1, _U2>&& __p)
00135     {
00136       first = std::move(__p.first);
00137       second = std::move(__p.second);
00138       return *this;
00139     }
00140 
00141       void
00142       swap(pair& __p)
00143       {
00144     using std::swap;
00145     swap(first, __p.first);
00146     swap(second, __p.second);   
00147       }
00148 #endif
00149     };
00150 
00151   /// Two pairs of the same type are equal iff their members are equal.
00152   template<class _T1, class _T2>
00153     inline bool
00154     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
00155     { return __x.first == __y.first && __x.second == __y.second; }
00156 
00157   /// <http://gcc.gnu.org/onlinedocs/libstdc++/manual/utilities.html>
00158   template<class _T1, class _T2>
00159     inline bool
00160     operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
00161     { return __x.first < __y.first
00162          || (!(__y.first < __x.first) && __x.second < __y.second); }
00163 
00164   /// Uses @c operator== to find the result.
00165   template<class _T1, class _T2>
00166     inline bool
00167     operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
00168     { return !(__x == __y); }
00169 
00170   /// Uses @c operator< to find the result.
00171   template<class _T1, class _T2>
00172     inline bool
00173     operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
00174     { return __y < __x; }
00175 
00176   /// Uses @c operator< to find the result.
00177   template<class _T1, class _T2>
00178     inline bool
00179     operator<=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
00180     { return !(__y < __x); }
00181 
00182   /// Uses @c operator< to find the result.
00183   template<class _T1, class _T2>
00184     inline bool
00185     operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
00186     { return !(__x < __y); }
00187 
00188 #ifdef __GXX_EXPERIMENTAL_CXX0X__
00189   /// See std::pair::swap().
00190   // Note:  no std::swap overloads in C++03 mode, this has performance
00191   //        implications, see, eg, libstdc++/38466.
00192   template<class _T1, class _T2>
00193     inline void
00194     swap(pair<_T1, _T2>& __x, pair<_T1, _T2>& __y)
00195     { __x.swap(__y); }
00196 #endif
00197 
00198   /**
00199    *  @brief A convenience wrapper for creating a pair from two objects.
00200    *  @param  x  The first object.
00201    *  @param  y  The second object.
00202    *  @return   A newly-constructed pair<> object of the appropriate type.
00203    *
00204    *  The standard requires that the objects be passed by reference-to-const,
00205    *  but LWG issue #181 says they should be passed by const value.  We follow
00206    *  the LWG by default.
00207    */
00208   // _GLIBCXX_RESOLVE_LIB_DEFECTS
00209   // 181.  make_pair() unintended behavior
00210 #ifndef __GXX_EXPERIMENTAL_CXX0X__
00211   template<class _T1, class _T2>
00212     inline pair<_T1, _T2>
00213     make_pair(_T1 __x, _T2 __y)
00214     { return pair<_T1, _T2>(__x, __y); }
00215 #else
00216   template<typename _Tp>
00217     class reference_wrapper;
00218 
00219   // Helper which adds a reference to a type when given a reference_wrapper
00220   template<typename _Tp>
00221     struct __strip_reference_wrapper
00222     {
00223       typedef _Tp __type;
00224     };
00225 
00226   template<typename _Tp>
00227     struct __strip_reference_wrapper<reference_wrapper<_Tp> >
00228     {
00229       typedef _Tp& __type;
00230     };
00231 
00232   template<typename _Tp>
00233     struct __strip_reference_wrapper<const reference_wrapper<_Tp> >
00234     {
00235       typedef _Tp& __type;
00236     };
00237 
00238   template<typename _Tp>
00239     struct __decay_and_strip
00240     {
00241       typedef typename __strip_reference_wrapper<
00242     typename decay<_Tp>::type>::__type __type;
00243     };
00244 
00245   // NB: DR 706.
00246   template<class _T1, class _T2>
00247     inline pair<typename __decay_and_strip<_T1>::__type,
00248         typename __decay_and_strip<_T2>::__type>
00249     make_pair(_T1&& __x, _T2&& __y)
00250     {
00251       return pair<typename __decay_and_strip<_T1>::__type,
00252               typename __decay_and_strip<_T2>::__type>
00253     (std::forward<_T1>(__x), std::forward<_T2>(__y));
00254     }
00255 #endif
00256 
00257 _GLIBCXX_END_NAMESPACE
00258 
00259 #endif /* _STL_PAIR_H */