stl_pair.h

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// Pair implementation -*- C++ -*-

// Copyright (C) 2001-2015 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/*
 *
 * Copyright (c) 1994
 * Hewlett-Packard Company
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Hewlett-Packard Company makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 *
 * Copyright (c) 1996,1997
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 */

/** @file bits/stl_pair.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{utility}
 */

#ifndef _STL_PAIR_H
#define _STL_PAIR_H 1

#include <bits/move.h> // for std::move / std::forward, and std::swap

#if __cplusplus >= 201103L
#include <type_traits> // for std::__decay_and_strip too
#endif

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  /**
   *  @addtogroup utilities
   *  @{
   */

#if __cplusplus >= 201103L
  /// piecewise_construct_t
  struct piecewise_construct_t { };

  /// piecewise_construct
  constexpr piecewise_construct_t piecewise_construct = piecewise_construct_t();

  // Forward declarations.
  template<typename...>
    class tuple;

  template<std::size_t...>
    struct _Index_tuple;
#endif

 /**
   *  @brief Struct holding two objects of arbitrary type.
   *
   *  @tparam _T1  Type of first object.
   *  @tparam _T2  Type of second object.
   */
  template<class _T1, class _T2>
    struct pair
    {
      typedef _T1 first_type;    /// @c first_type is the first bound type
      typedef _T2 second_type;   /// @c second_type is the second bound type

      _T1 first;                 /// @c first is a copy of the first object
      _T2 second;                /// @c second is a copy of the second object

      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 265.  std::pair::pair() effects overly restrictive
      /** The default constructor creates @c first and @c second using their
       *  respective default constructors.  */
      _GLIBCXX_CONSTEXPR pair()
      : first(), second() { }

      /** Two objects may be passed to a @c pair constructor to be copied.  */
      _GLIBCXX_CONSTEXPR pair(const _T1& __a, const _T2& __b)
      : first(__a), second(__b) { }

      /** There is also a templated copy ctor for the @c pair class itself.  */
#if __cplusplus < 201103L
      template<class _U1, class _U2>
        pair(const pair<_U1, _U2>& __p)
        : first(__p.first), second(__p.second) { }
#else
      template<class _U1, class _U2, class = typename
               enable_if<__and_<is_convertible<const _U1&, _T1>,
                                is_convertible<const _U2&, _T2>>::value>::type>
        constexpr pair(const pair<_U1, _U2>& __p)
        : first(__p.first), second(__p.second) { }

      constexpr pair(const pair&) = default;
      constexpr pair(pair&&) = default;

      // DR 811.
      template<class _U1, class = typename
               enable_if<is_convertible<_U1, _T1>::value>::type>
        constexpr pair(_U1&& __x, const _T2& __y)
        : first(std::forward<_U1>(__x)), second(__y) { }

      template<class _U2, class = typename
               enable_if<is_convertible<_U2, _T2>::value>::type>
        constexpr pair(const _T1& __x, _U2&& __y)
        : first(__x), second(std::forward<_U2>(__y)) { }

      template<class _U1, class _U2, class = typename
               enable_if<__and_<is_convertible<_U1, _T1>,
                                is_convertible<_U2, _T2>>::value>::type>
        constexpr pair(_U1&& __x, _U2&& __y)
        : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }

      template<class _U1, class _U2, class = typename
               enable_if<__and_<is_convertible<_U1, _T1>,
                                is_convertible<_U2, _T2>>::value>::type>
        constexpr pair(pair<_U1, _U2>&& __p)
        : first(std::forward<_U1>(__p.first)),
          second(std::forward<_U2>(__p.second)) { }

      template<typename... _Args1, typename... _Args2>
        pair(piecewise_construct_t, tuple<_Args1...>, tuple<_Args2...>);

      pair&
      operator=(const pair& __p)
      {
        first = __p.first;
        second = __p.second;
        return *this;
      }

      pair&
      operator=(pair&& __p)
      noexcept(__and_<is_nothrow_move_assignable<_T1>,
                      is_nothrow_move_assignable<_T2>>::value)
      {
        first = std::forward<first_type>(__p.first);
        second = std::forward<second_type>(__p.second);
        return *this;
      }

      template<class _U1, class _U2>
        pair&
        operator=(const pair<_U1, _U2>& __p)
        {
          first = __p.first;
          second = __p.second;
          return *this;
        }

      template<class _U1, class _U2>
        pair&
        operator=(pair<_U1, _U2>&& __p)
        {
          first = std::forward<_U1>(__p.first);
          second = std::forward<_U2>(__p.second);
          return *this;
        }

      void
      swap(pair& __p)
      noexcept(noexcept(swap(first, __p.first))
               && noexcept(swap(second, __p.second)))
      {
        using std::swap;
        swap(first, __p.first);
        swap(second, __p.second);
      }

    private:
      template<typename... _Args1, std::size_t... _Indexes1,
               typename... _Args2, std::size_t... _Indexes2>
        pair(tuple<_Args1...>&, tuple<_Args2...>&,
             _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
#endif
    };

  /// Two pairs of the same type are equal iff their members are equal.
  template<class _T1, class _T2>
    inline _GLIBCXX_CONSTEXPR bool
    operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
    { return __x.first == __y.first && __x.second == __y.second; }

  /// <http://gcc.gnu.org/onlinedocs/libstdc++/manual/utilities.html>
  template<class _T1, class _T2>
    inline _GLIBCXX_CONSTEXPR bool
    operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
    { return __x.first < __y.first
             || (!(__y.first < __x.first) && __x.second < __y.second); }

  /// Uses @c operator== to find the result.
  template<class _T1, class _T2>
    inline _GLIBCXX_CONSTEXPR bool
    operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
    { return !(__x == __y); }

  /// Uses @c operator< to find the result.
  template<class _T1, class _T2>
    inline _GLIBCXX_CONSTEXPR bool
    operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
    { return __y < __x; }

  /// Uses @c operator< to find the result.
  template<class _T1, class _T2>
    inline _GLIBCXX_CONSTEXPR bool
    operator<=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
    { return !(__y < __x); }

  /// Uses @c operator< to find the result.
  template<class _T1, class _T2>
    inline _GLIBCXX_CONSTEXPR bool
    operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
    { return !(__x < __y); }

#if __cplusplus >= 201103L
  /// See std::pair::swap().
  // Note:  no std::swap overloads in C++03 mode, this has performance
  //        implications, see, eg, libstdc++/38466.
  template<class _T1, class _T2>
    inline void
    swap(pair<_T1, _T2>& __x, pair<_T1, _T2>& __y)
    noexcept(noexcept(__x.swap(__y)))
    { __x.swap(__y); }
#endif

  /**
   *  @brief A convenience wrapper for creating a pair from two objects.
   *  @param  __x  The first object.
   *  @param  __y  The second object.
   *  @return   A newly-constructed pair<> object of the appropriate type.
   *
   *  The standard requires that the objects be passed by reference-to-const,
   *  but LWG issue #181 says they should be passed by const value.  We follow
   *  the LWG by default.
   */
  // _GLIBCXX_RESOLVE_LIB_DEFECTS
  // 181.  make_pair() unintended behavior
#if __cplusplus >= 201103L
  // NB: DR 706.
  template<class _T1, class _T2>
    constexpr pair<typename __decay_and_strip<_T1>::__type,
                   typename __decay_and_strip<_T2>::__type>
    make_pair(_T1&& __x, _T2&& __y)
    {
      typedef typename __decay_and_strip<_T1>::__type __ds_type1;
      typedef typename __decay_and_strip<_T2>::__type __ds_type2;
      typedef pair<__ds_type1, __ds_type2>            __pair_type;
      return __pair_type(std::forward<_T1>(__x), std::forward<_T2>(__y));
    }
#else
  template<class _T1, class _T2>
    inline pair<_T1, _T2>
    make_pair(_T1 __x, _T2 __y)
    { return pair<_T1, _T2>(__x, __y); }
#endif

  /// @}

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#endif /* _STL_PAIR_H */