libstdc++-v3/include/bits/stl_pair.h

   1 // Pair implementation -*- C++ -*-
   2
   3 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
   4 // 2010, 2011, 2012
   5 // Free Software Foundation, Inc.
   6 //
   7 // This file is part of the GNU ISO C++ Library.  This library is free
   8 // software; you can redistribute it and/or modify it under the
   9 // terms of the GNU General Public License as published by the
  10 // Free Software Foundation; either version 3, or (at your option)
  11 // any later version.
  12
  13 // This library is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17
  18 // Under Section 7 of GPL version 3, you are granted additional
  19 // permissions described in the GCC Runtime Library Exception, version
  20 // 3.1, as published by the Free Software Foundation.
  21
  22 // You should have received a copy of the GNU General Public License and
  23 // a copy of the GCC Runtime Library Exception along with this program;
  24 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  25 // <http://www.gnu.org/licenses/>.
  26
  27 /*
  28  *
  29  * Copyright (c) 1994
  30  * Hewlett-Packard Company
  31  *
  32  * Permission to use, copy, modify, distribute and sell this software
  33  * and its documentation for any purpose is hereby granted without fee,
  34  * provided that the above copyright notice appear in all copies and
  35  * that both that copyright notice and this permission notice appear
  36  * in supporting documentation.  Hewlett-Packard Company makes no
  37  * representations about the suitability of this software for any
  38  * purpose.  It is provided "as is" without express or implied warranty.
  39  *
  40  *
  41  * Copyright (c) 1996,1997
  42  * Silicon Graphics Computer Systems, Inc.
  43  *
  44  * Permission to use, copy, modify, distribute and sell this software
  45  * and its documentation for any purpose is hereby granted without fee,
  46  * provided that the above copyright notice appear in all copies and
  47  * that both that copyright notice and this permission notice appear
  48  * in supporting documentation.  Silicon Graphics makes no
  49  * representations about the suitability of this software for any
  50  * purpose.  It is provided "as is" without express or implied warranty.
  51  */
  52
  53 /** @file bits/stl_pair.h
  54  *  This is an internal header file, included by other library headers.
  55  *  Do not attempt to use it directly. @headername{utility}
  56  */
  57
  58 #ifndef _STL_PAIR_H
  59 #define _STL_PAIR_H 1
  60
  61 #include <bits/move.h> // for std::move / std::forward, and std::swap
  62
  63 #if __cplusplus >= 201103L
  64 #include <type_traits> // for std::__decay_and_strip too
  65 #endif
  66
  67 namespace std _GLIBCXX_VISIBILITY(default)
  68 {
  69 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  70
  71 #if __cplusplus >= 201103L
  72   /// piecewise_construct_t
  73   struct piecewise_construct_t { };
  74
  75   /// piecewise_construct
  76   constexpr piecewise_construct_t piecewise_construct = piecewise_construct_t();
  77
  78   // Forward declarations.
  79   template<typename...>
  80     class tuple;
  81
  82   template<std::size_t...>
  83     struct _Index_tuple;
  84 #endif
  85
  86  /**
  87    *  @brief Struct holding two objects of arbitrary type.
  88    *
  89    *  @tparam _T1  Type of first object.
  90    *  @tparam _T2  Type of second object.
  91    */
  92   template<class _T1, class _T2>
  93     struct pair
  94     {
  95       typedef _T1 first_type;    /// @c first_type is the first bound type
  96       typedef _T2 second_type;   /// @c second_type is the second bound type
  97
  98       _T1 first;                 /// @c first is a copy of the first object
  99       _T2 second;                /// @c second is a copy of the second object
 100
 101       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 102       // 265.  std::pair::pair() effects overly restrictive
 103       /** The default constructor creates @c first and @c second using their
 104        *  respective default constructors.  */
 105       _GLIBCXX_CONSTEXPR pair()
 106       : first(), second() { }
 107
 108       /** Two objects may be passed to a @c pair constructor to be copied.  */
 109       _GLIBCXX_CONSTEXPR pair(const _T1& __a, const _T2& __b)
 110       : first(__a), second(__b) { }
 111
 112       /** There is also a templated copy ctor for the @c pair class itself.  */
 113 #if __cplusplus < 201103L
 114       template<class _U1, class _U2>
 115         pair(const pair<_U1, _U2>& __p)
 116         : first(__p.first), second(__p.second) { }
 117 #else
 118       template<class _U1, class _U2, class = typename
 119                enable_if<__and_<is_convertible<const _U1&, _T1>,
 120                                 is_convertible<const _U2&, _T2>>::value>::type>
 121         constexpr pair(const pair<_U1, _U2>& __p)
 122         : first(__p.first), second(__p.second) { }
 123
 124       constexpr pair(const pair&) = default;
 125       constexpr pair(pair&&) = default;
 126
 127       // DR 811.
 128       template<class _U1, class = typename
 129                enable_if<is_convertible<_U1, _T1>::value>::type>
 130         constexpr pair(_U1&& __x, const _T2& __y)
 131         : first(std::forward<_U1>(__x)), second(__y) { }
 132
 133       template<class _U2, class = typename
 134                enable_if<is_convertible<_U2, _T2>::value>::type>
 135         constexpr pair(const _T1& __x, _U2&& __y)
 136         : first(__x), second(std::forward<_U2>(__y)) { }
 137
 138       template<class _U1, class _U2, class = typename
 139                enable_if<__and_<is_convertible<_U1, _T1>,
 140                                 is_convertible<_U2, _T2>>::value>::type>
 141         constexpr pair(_U1&& __x, _U2&& __y)
 142         : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
 143
 144       template<class _U1, class _U2, class = typename
 145                enable_if<__and_<is_convertible<_U1, _T1>,
 146                                 is_convertible<_U2, _T2>>::value>::type>
 147         constexpr pair(pair<_U1, _U2>&& __p)
 148         : first(std::forward<_U1>(__p.first)),
 149           second(std::forward<_U2>(__p.second)) { }
 150
 151       template<typename... _Args1, typename... _Args2>
 152         pair(piecewise_construct_t, tuple<_Args1...>, tuple<_Args2...>);
 153
 154       pair&
 155       operator=(const pair& __p)
 156       {
 157         first = __p.first;
 158         second = __p.second;
 159         return *this;
 160       }
 161
 162       pair&
 163       operator=(pair&& __p)
 164       noexcept(__and_<is_nothrow_move_assignable<_T1>,
 165                       is_nothrow_move_assignable<_T2>>::value)
 166       {
 167         first = std::forward<first_type>(__p.first);
 168         second = std::forward<second_type>(__p.second);
 169         return *this;
 170       }
 171
 172       template<class _U1, class _U2>
 173         pair&
 174         operator=(const pair<_U1, _U2>& __p)
 175         {
 176           first = __p.first;
 177           second = __p.second;
 178           return *this;
 179         }
 180
 181       template<class _U1, class _U2>
 182         pair&
 183         operator=(pair<_U1, _U2>&& __p)
 184         {
 185           first = std::forward<_U1>(__p.first);
 186           second = std::forward<_U2>(__p.second);
 187           return *this;
 188         }
 189
 190       void
 191       swap(pair& __p)
 192       noexcept(noexcept(swap(first, __p.first))
 193                && noexcept(swap(second, __p.second)))
 194       {
 195         using std::swap;
 196         swap(first, __p.first);
 197         swap(second, __p.second);
 198       }
 199
 200     private:
 201       template<typename... _Args1, std::size_t... _Indexes1,
 202                typename... _Args2, std::size_t... _Indexes2>
 203         pair(tuple<_Args1...>&, tuple<_Args2...>&,
 204              _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
 205 #endif
 206     };
 207
 208   /// Two pairs of the same type are equal iff their members are equal.
 209   template<class _T1, class _T2>
 210     inline _GLIBCXX_CONSTEXPR bool
 211     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
 212     { return __x.first == __y.first && __x.second == __y.second; }
 213
 214   /// <http://gcc.gnu.org/onlinedocs/libstdc++/manual/utilities.html>
 215   template<class _T1, class _T2>
 216     inline _GLIBCXX_CONSTEXPR bool
 217     operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
 218     { return __x.first < __y.first
 219              || (!(__y.first < __x.first) && __x.second < __y.second); }
 220
 221   /// Uses @c operator== to find the result.
 222   template<class _T1, class _T2>
 223     inline _GLIBCXX_CONSTEXPR bool
 224     operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
 225     { return !(__x == __y); }
 226
 227   /// Uses @c operator< to find the result.
 228   template<class _T1, class _T2>
 229     inline _GLIBCXX_CONSTEXPR bool
 230     operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
 231     { return __y < __x; }
 232
 233   /// Uses @c operator< to find the result.
 234   template<class _T1, class _T2>
 235     inline _GLIBCXX_CONSTEXPR bool
 236     operator<=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
 237     { return !(__y < __x); }
 238
 239   /// Uses @c operator< to find the result.
 240   template<class _T1, class _T2>
 241     inline _GLIBCXX_CONSTEXPR bool
 242     operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
 243     { return !(__x < __y); }
 244
 245 #if __cplusplus >= 201103L
 246   /// See std::pair::swap().
 247   // Note:  no std::swap overloads in C++03 mode, this has performance
 248   //        implications, see, eg, libstdc++/38466.
 249   template<class _T1, class _T2>
 250     inline void
 251     swap(pair<_T1, _T2>& __x, pair<_T1, _T2>& __y)
 252     noexcept(noexcept(__x.swap(__y)))
 253     { __x.swap(__y); }
 254 #endif
 255
 256   /**
 257    *  @brief A convenience wrapper for creating a pair from two objects.
 258    *  @param  __x  The first object.
 259    *  @param  __y  The second object.
 260    *  @return   A newly-constructed pair<> object of the appropriate type.
 261    *
 262    *  The standard requires that the objects be passed by reference-to-const,
 263    *  but LWG issue #181 says they should be passed by const value.  We follow
 264    *  the LWG by default.
 265    */
 266   // _GLIBCXX_RESOLVE_LIB_DEFECTS
 267   // 181.  make_pair() unintended behavior
 268 #if __cplusplus >= 201103L
 269   // NB: DR 706.
 270   template<class _T1, class _T2>
 271     constexpr pair<typename __decay_and_strip<_T1>::__type,
 272                    typename __decay_and_strip<_T2>::__type>
 273     make_pair(_T1&& __x, _T2&& __y)
 274     {
 275       typedef typename __decay_and_strip<_T1>::__type __ds_type1;
 276       typedef typename __decay_and_strip<_T2>::__type __ds_type2;
 277       typedef pair<__ds_type1, __ds_type2>            __pair_type;
 278       return __pair_type(std::forward<_T1>(__x), std::forward<_T2>(__y));
 279     }
 280 #else
 281   template<class _T1, class _T2>
 282     inline pair<_T1, _T2>
 283     make_pair(_T1 __x, _T2 __y)
 284     { return pair<_T1, _T2>(__x, __y); }
 285 #endif
 286
 287 _GLIBCXX_END_NAMESPACE_VERSION
 288 } // namespace
 289
 290 #endif /* _STL_PAIR_H */