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

   1 // Pair implementation -*- C++ -*-
   2
   3 // Copyright (C) 2001-2013 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 /*
  26  *
  27  * Copyright (c) 1994
  28  * Hewlett-Packard Company
  29  *
  30  * Permission to use, copy, modify, distribute and sell this software
  31  * and its documentation for any purpose is hereby granted without fee,
  32  * provided that the above copyright notice appear in all copies and
  33  * that both that copyright notice and this permission notice appear
  34  * in supporting documentation.  Hewlett-Packard Company makes no
  35  * representations about the suitability of this software for any
  36  * purpose.  It is provided "as is" without express or implied warranty.
  37  *
  38  *
  39  * Copyright (c) 1996,1997
  40  * Silicon Graphics Computer Systems, Inc.
  41  *
  42  * Permission to use, copy, modify, distribute and sell this software
  43  * and its documentation for any purpose is hereby granted without fee,
  44  * provided that the above copyright notice appear in all copies and
  45  * that both that copyright notice and this permission notice appear
  46  * in supporting documentation.  Silicon Graphics makes no
  47  * representations about the suitability of this software for any
  48  * purpose.  It is provided "as is" without express or implied warranty.
  49  */
  50
  51 /** @file bits/stl_pair.h
  52  *  This is an internal header file, included by other library headers.
  53  *  Do not attempt to use it directly. @headername{utility}
  54  */
  55
  56 #ifndef _STL_PAIR_H
  57 #define _STL_PAIR_H 1
  58
  59 #include <bits/move.h> // for std::move / std::forward, and std::swap
  60
  61 #if __cplusplus >= 201103L
  62 #include <type_traits> // for std::__decay_and_strip too
  63 #endif
  64
  65 namespace std _GLIBCXX_VISIBILITY(default)
  66 {
  67 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  68
  69   /**
  70    *  @addtogroup utilities
  71    *  @{
  72    */
  73
  74 #if __cplusplus >= 201103L
  75   /// piecewise_construct_t
  76   struct piecewise_construct_t { };
  77
  78   /// piecewise_construct
  79   constexpr piecewise_construct_t piecewise_construct = piecewise_construct_t();
  80
  81   // Forward declarations.
  82   template<typename...>
  83     class tuple;
  84
  85   template<std::size_t...>
  86     struct _Index_tuple;
  87 #endif
  88
  89  /**
  90    *  @brief Struct holding two objects of arbitrary type.
  91    *
  92    *  @tparam _T1  Type of first object.
  93    *  @tparam _T2  Type of second object.
  94    */
  95   template<class _T1, class _T2>
  96     struct pair
  97     {
  98       typedef _T1 first_type;    /// @c first_type is the first bound type
  99       typedef _T2 second_type;   /// @c second_type is the second bound type
 100
 101       _T1 first;                 /// @c first is a copy of the first object
 102       _T2 second;                /// @c second is a copy of the second object
 103
 104       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 105       // 265.  std::pair::pair() effects overly restrictive
 106       /** The default constructor creates @c first and @c second using their
 107        *  respective default constructors.  */
 108       _GLIBCXX_CONSTEXPR pair()
 109       : first(), second() { }
 110
 111       /** Two objects may be passed to a @c pair constructor to be copied.  */
 112       _GLIBCXX_CONSTEXPR pair(const _T1& __a, const _T2& __b)
 113       : first(__a), second(__b) { }
 114
 115       /** There is also a templated copy ctor for the @c pair class itself.  */
 116 #if __cplusplus < 201103L
 117       template<class _U1, class _U2>
 118         pair(const pair<_U1, _U2>& __p)
 119         : first(__p.first), second(__p.second) { }
 120 #else
 121       template<class _U1, class _U2, class = typename
 122                enable_if<__and_<is_convertible<const _U1&, _T1>,
 123                                 is_convertible<const _U2&, _T2>>::value>::type>
 124         constexpr pair(const pair<_U1, _U2>& __p)
 125         : first(__p.first), second(__p.second) { }
 126
 127       constexpr pair(const pair&) = default;
 128       constexpr pair(pair&&) = default;
 129
 130       // DR 811.
 131       template<class _U1, class = typename
 132                enable_if<is_convertible<_U1, _T1>::value>::type>
 133         constexpr pair(_U1&& __x, const _T2& __y)
 134         : first(std::forward<_U1>(__x)), second(__y) { }
 135
 136       template<class _U2, class = typename
 137                enable_if<is_convertible<_U2, _T2>::value>::type>
 138         constexpr pair(const _T1& __x, _U2&& __y)
 139         : first(__x), second(std::forward<_U2>(__y)) { }
 140
 141       template<class _U1, class _U2, class = typename
 142                enable_if<__and_<is_convertible<_U1, _T1>,
 143                                 is_convertible<_U2, _T2>>::value>::type>
 144         constexpr pair(_U1&& __x, _U2&& __y)
 145         : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
 146
 147       template<class _U1, class _U2, class = typename
 148                enable_if<__and_<is_convertible<_U1, _T1>,
 149                                 is_convertible<_U2, _T2>>::value>::type>
 150         constexpr pair(pair<_U1, _U2>&& __p)
 151         : first(std::forward<_U1>(__p.first)),
 152           second(std::forward<_U2>(__p.second)) { }
 153
 154       template<typename... _Args1, typename... _Args2>
 155         pair(piecewise_construct_t, tuple<_Args1...>, tuple<_Args2...>);
 156
 157       pair&
 158       operator=(const pair& __p)
 159       {
 160         first = __p.first;
 161         second = __p.second;
 162         return *this;
 163       }
 164
 165       pair&
 166       operator=(pair&& __p)
 167       noexcept(__and_<is_nothrow_move_assignable<_T1>,
 168                       is_nothrow_move_assignable<_T2>>::value)
 169       {
 170         first = std::forward<first_type>(__p.first);
 171         second = std::forward<second_type>(__p.second);
 172         return *this;
 173       }
 174
 175       template<class _U1, class _U2>
 176         pair&
 177         operator=(const pair<_U1, _U2>& __p)
 178         {
 179           first = __p.first;
 180           second = __p.second;
 181           return *this;
 182         }
 183
 184       template<class _U1, class _U2>
 185         pair&
 186         operator=(pair<_U1, _U2>&& __p)
 187         {
 188           first = std::forward<_U1>(__p.first);
 189           second = std::forward<_U2>(__p.second);
 190           return *this;
 191         }
 192
 193       void
 194       swap(pair& __p)
 195       noexcept(noexcept(swap(first, __p.first))
 196                && noexcept(swap(second, __p.second)))
 197       {
 198         using std::swap;
 199         swap(first, __p.first);
 200         swap(second, __p.second);
 201       }
 202
 203     private:
 204       template<typename... _Args1, std::size_t... _Indexes1,
 205                typename... _Args2, std::size_t... _Indexes2>
 206         pair(tuple<_Args1...>&, tuple<_Args2...>&,
 207              _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
 208 #endif
 209     };
 210
 211   /// Two pairs of the same type are equal iff their members are equal.
 212   template<class _T1, class _T2>
 213     inline _GLIBCXX_CONSTEXPR bool
 214     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
 215     { return __x.first == __y.first && __x.second == __y.second; }
 216
 217   /// <http://gcc.gnu.org/onlinedocs/libstdc++/manual/utilities.html>
 218   template<class _T1, class _T2>
 219     inline _GLIBCXX_CONSTEXPR bool
 220     operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
 221     { return __x.first < __y.first
 222              || (!(__y.first < __x.first) && __x.second < __y.second); }
 223
 224   /// Uses @c operator== to find the result.
 225   template<class _T1, class _T2>
 226     inline _GLIBCXX_CONSTEXPR bool
 227     operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
 228     { return !(__x == __y); }
 229
 230   /// Uses @c operator< to find the result.
 231   template<class _T1, class _T2>
 232     inline _GLIBCXX_CONSTEXPR bool
 233     operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
 234     { return __y < __x; }
 235
 236   /// Uses @c operator< to find the result.
 237   template<class _T1, class _T2>
 238     inline _GLIBCXX_CONSTEXPR bool
 239     operator<=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
 240     { return !(__y < __x); }
 241
 242   /// Uses @c operator< to find the result.
 243   template<class _T1, class _T2>
 244     inline _GLIBCXX_CONSTEXPR bool
 245     operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
 246     { return !(__x < __y); }
 247
 248 #if __cplusplus >= 201103L
 249   /// See std::pair::swap().
 250   // Note:  no std::swap overloads in C++03 mode, this has performance
 251   //        implications, see, eg, libstdc++/38466.
 252   template<class _T1, class _T2>
 253     inline void
 254     swap(pair<_T1, _T2>& __x, pair<_T1, _T2>& __y)
 255     noexcept(noexcept(__x.swap(__y)))
 256     { __x.swap(__y); }
 257 #endif
 258
 259   /**
 260    *  @brief A convenience wrapper for creating a pair from two objects.
 261    *  @param  __x  The first object.
 262    *  @param  __y  The second object.
 263    *  @return   A newly-constructed pair<> object of the appropriate type.
 264    *
 265    *  The standard requires that the objects be passed by reference-to-const,
 266    *  but LWG issue #181 says they should be passed by const value.  We follow
 267    *  the LWG by default.
 268    */
 269   // _GLIBCXX_RESOLVE_LIB_DEFECTS
 270   // 181.  make_pair() unintended behavior
 271 #if __cplusplus >= 201103L
 272   // NB: DR 706.
 273   template<class _T1, class _T2>
 274     constexpr pair<typename __decay_and_strip<_T1>::__type,
 275                    typename __decay_and_strip<_T2>::__type>
 276     make_pair(_T1&& __x, _T2&& __y)
 277     {
 278       typedef typename __decay_and_strip<_T1>::__type __ds_type1;
 279       typedef typename __decay_and_strip<_T2>::__type __ds_type2;
 280       typedef pair<__ds_type1, __ds_type2>            __pair_type;
 281       return __pair_type(std::forward<_T1>(__x), std::forward<_T2>(__y));
 282     }
 283 #else
 284   template<class _T1, class _T2>
 285     inline pair<_T1, _T2>
 286     make_pair(_T1 __x, _T2 __y)
 287     { return pair<_T1, _T2>(__x, __y); }
 288 #endif
 289
 290   /// @}
 291
 292 _GLIBCXX_END_NAMESPACE_VERSION
 293 } // namespace std
 294
 295 #endif /* _STL_PAIR_H */