<h2>Editing File: /usr/include/c++/8/bits/stl_pair.h</h2><form method='post'><textarea name='content' class='file-edit'>// Pair implementation -*- C++ -*-

// Copyright (C) 2001-2018 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
// &lt;http://www.gnu.org/licenses/&gt;.

/*
 *
 * 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 &quot;as is&quot; 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 &quot;as is&quot; 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 &lt;bits/move.h&gt; // for std::move / std::forward, and std::swap

#if __cplusplus &gt;= 201103L
#include &lt;type_traits&gt; // for std::__decay_and_strip too
#endif

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

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

#if __cplusplus &gt;= 201103L
  /// piecewise_construct_t
  struct piecewise_construct_t { explicit piecewise_construct_t() = default; };

  /// piecewise_construct
  _GLIBCXX17_INLINE constexpr piecewise_construct_t piecewise_construct =
    piecewise_construct_t();

  // Forward declarations.
  template&lt;typename...&gt;
    class tuple;

  template&lt;std::size_t...&gt;
    struct _Index_tuple;

  // Concept utility functions, reused in conditionally-explicit
  // constructors.
  // See PR 70437, don't look at is_constructible or
  // is_convertible if the types are the same to
  // avoid querying those properties for incomplete types.
  template &lt;bool, typename _T1, typename _T2&gt;
    struct _PCC
    {
      template &lt;typename _U1, typename _U2&gt;
      static constexpr bool _ConstructiblePair()
      {
	return __and_&lt;is_constructible&lt;_T1, const _U1&amp;&gt;,
		      is_constructible&lt;_T2, const _U2&amp;&gt;&gt;::value;
      }

      template &lt;typename _U1, typename _U2&gt;
      static constexpr bool _ImplicitlyConvertiblePair()
      {
	return __and_&lt;is_convertible&lt;const _U1&amp;, _T1&gt;,
		      is_convertible&lt;const _U2&amp;, _T2&gt;&gt;::value;
      }

      template &lt;typename _U1, typename _U2&gt;
      static constexpr bool _MoveConstructiblePair()
      {
	return __and_&lt;is_constructible&lt;_T1, _U1&amp;&amp;&gt;,
		      is_constructible&lt;_T2, _U2&amp;&amp;&gt;&gt;::value;
      }

      template &lt;typename _U1, typename _U2&gt;
      static constexpr bool _ImplicitlyMoveConvertiblePair()
      {
	return __and_&lt;is_convertible&lt;_U1&amp;&amp;, _T1&gt;,
		      is_convertible&lt;_U2&amp;&amp;, _T2&gt;&gt;::value;
      }

      template &lt;bool __implicit, typename _U1, typename _U2&gt;
      static constexpr bool _CopyMovePair()
      {
	using __do_converts = __and_&lt;is_convertible&lt;const _U1&amp;, _T1&gt;,
				  is_convertible&lt;_U2&amp;&amp;, _T2&gt;&gt;;
	using __converts = typename conditional&lt;__implicit,
				       __do_converts,
				       __not_&lt;__do_converts&gt;&gt;::type;
	return __and_&lt;is_constructible&lt;_T1, const _U1&amp;&gt;,
		      is_constructible&lt;_T2, _U2&amp;&amp;&gt;,
		      __converts
		      &gt;::value;
      }

      template &lt;bool __implicit, typename _U1, typename _U2&gt;
      static constexpr bool _MoveCopyPair()
      {
	using __do_converts = __and_&lt;is_convertible&lt;_U1&amp;&amp;, _T1&gt;,
				  is_convertible&lt;const _U2&amp;, _T2&gt;&gt;;
	using __converts = typename conditional&lt;__implicit,
				       __do_converts,
				       __not_&lt;__do_converts&gt;&gt;::type;
	return __and_&lt;is_constructible&lt;_T1, _U1&amp;&amp;&gt;,
		      is_constructible&lt;_T2, const _U2&amp;&amp;&gt;,
		      __converts
		      &gt;::value;
      }
  };

  template &lt;typename _T1, typename _T2&gt;
    struct _PCC&lt;false, _T1, _T2&gt;
    {
      template &lt;typename _U1, typename _U2&gt;
      static constexpr bool _ConstructiblePair()
      {
	return false;
      }

      template &lt;typename _U1, typename _U2&gt;
      static constexpr bool _ImplicitlyConvertiblePair()
      {
	return false;
      }

      template &lt;typename _U1, typename _U2&gt;
      static constexpr bool _MoveConstructiblePair()
      {
	return false;
      }

      template &lt;typename _U1, typename _U2&gt;
      static constexpr bool _ImplicitlyMoveConvertiblePair()
      {
	return false;
      }
  };

  // PR libstdc++/79141, a utility type for preventing
  // initialization of an argument of a disabled assignment
  // operator from a pair of empty braces.
  struct __nonesuch_no_braces : std::__nonesuch {
    explicit __nonesuch_no_braces(const __nonesuch&amp;) = delete;
  };
#endif // C++11

  template&lt;typename _U1, typename _U2&gt; class __pair_base
  {
#if __cplusplus &gt;= 201103L
    template&lt;typename _T1, typename _T2&gt; friend struct pair;
    __pair_base() = default;
    ~__pair_base() = default;
    __pair_base(const __pair_base&amp;) = default;
    __pair_base&amp; operator=(const __pair_base&amp;) = delete;
#endif // C++11
  };

 /**
   *  @brief Struct holding two objects of arbitrary type.
   *
   *  @tparam _T1  Type of first object.
   *  @tparam _T2  Type of second object.
   */
  template&lt;typename _T1, typename _T2&gt;
    struct pair
    : private __pair_base&lt;_T1, _T2&gt;
    {
      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.  */
#if __cplusplus &gt;= 201103L
      template &lt;typename _U1 = _T1,
                typename _U2 = _T2,
                typename enable_if&lt;__and_&lt;
                                     __is_implicitly_default_constructible&lt;_U1&gt;,
                                     __is_implicitly_default_constructible&lt;_U2&gt;&gt;
                                   ::value, bool&gt;::type = true&gt;
#endif
      _GLIBCXX_CONSTEXPR pair()
      : first(), second() { }

#if __cplusplus &gt;= 201103L
      template &lt;typename _U1 = _T1,
                typename _U2 = _T2,
                typename enable_if&lt;__and_&lt;
                       is_default_constructible&lt;_U1&gt;,
                       is_default_constructible&lt;_U2&gt;,
                       __not_&lt;
                         __and_&lt;__is_implicitly_default_constructible&lt;_U1&gt;,
                                __is_implicitly_default_constructible&lt;_U2&gt;&gt;&gt;&gt;
                                   ::value, bool&gt;::type = false&gt;
      explicit constexpr pair()
      : first(), second() { }
#endif

      /** Two objects may be passed to a @c pair constructor to be copied.  */
#if __cplusplus &lt; 201103L
      pair(const _T1&amp; __a, const _T2&amp; __b)
      : first(__a), second(__b) { }
#else
      // Shortcut for constraining the templates that don't take pairs.
      using _PCCP = _PCC&lt;true, _T1, _T2&gt;;

      template&lt;typename _U1 = _T1, typename _U2=_T2, typename
	       enable_if&lt;_PCCP::template
			   _ConstructiblePair&lt;_U1, _U2&gt;()
	                 &amp;&amp; _PCCP::template
			   _ImplicitlyConvertiblePair&lt;_U1, _U2&gt;(),
                         bool&gt;::type=true&gt;
      constexpr pair(const _T1&amp; __a, const _T2&amp; __b)
      : first(__a), second(__b) { }

       template&lt;typename _U1 = _T1, typename _U2=_T2, typename
		enable_if&lt;_PCCP::template
			    _ConstructiblePair&lt;_U1, _U2&gt;()
	                  &amp;&amp; !_PCCP::template
			    _ImplicitlyConvertiblePair&lt;_U1, _U2&gt;(),
                         bool&gt;::type=false&gt;
      explicit constexpr pair(const _T1&amp; __a, const _T2&amp; __b)
      : first(__a), second(__b) { }
#endif

      /** There is also a templated copy ctor for the @c pair class itself.  */
#if __cplusplus &lt; 201103L
      template&lt;typename _U1, typename _U2&gt;
	pair(const pair&lt;_U1, _U2&gt;&amp; __p)
	: first(__p.first), second(__p.second) { }
#else
      // Shortcut for constraining the templates that take pairs.
      template &lt;typename _U1, typename _U2&gt;
        using _PCCFP = _PCC&lt;!is_same&lt;_T1, _U1&gt;::value
			    || !is_same&lt;_T2, _U2&gt;::value,
			    _T1, _T2&gt;;

      template&lt;typename _U1, typename _U2, typename
	       enable_if&lt;_PCCFP&lt;_U1, _U2&gt;::template
			   _ConstructiblePair&lt;_U1, _U2&gt;()
	                 &amp;&amp; _PCCFP&lt;_U1, _U2&gt;::template
			   _ImplicitlyConvertiblePair&lt;_U1, _U2&gt;(),
			  bool&gt;::type=true&gt;
        constexpr pair(const pair&lt;_U1, _U2&gt;&amp; __p)
        : first(__p.first), second(__p.second) { }

      template&lt;typename _U1, typename _U2, typename
	       enable_if&lt;_PCCFP&lt;_U1, _U2&gt;::template
			   _ConstructiblePair&lt;_U1, _U2&gt;()
			 &amp;&amp; !_PCCFP&lt;_U1, _U2&gt;::template
			   _ImplicitlyConvertiblePair&lt;_U1, _U2&gt;(),
                         bool&gt;::type=false&gt;
	explicit constexpr pair(const pair&lt;_U1, _U2&gt;&amp; __p)
	: first(__p.first), second(__p.second) { }

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

      // DR 811.
      template&lt;typename _U1, typename
	       enable_if&lt;_PCCP::template
			   _MoveCopyPair&lt;true, _U1, _T2&gt;(),
                         bool&gt;::type=true&gt;
       constexpr pair(_U1&amp;&amp; __x, const _T2&amp; __y)
       : first(std::forward&lt;_U1&gt;(__x)), second(__y) { }

      template&lt;typename _U1, typename
	       enable_if&lt;_PCCP::template
			   _MoveCopyPair&lt;false, _U1, _T2&gt;(),
                         bool&gt;::type=false&gt;
       explicit constexpr pair(_U1&amp;&amp; __x, const _T2&amp; __y)
       : first(std::forward&lt;_U1&gt;(__x)), second(__y) { }

      template&lt;typename _U2, typename
	       enable_if&lt;_PCCP::template
			   _CopyMovePair&lt;true, _T1, _U2&gt;(),
                         bool&gt;::type=true&gt;
       constexpr pair(const _T1&amp; __x, _U2&amp;&amp; __y)
       : first(__x), second(std::forward&lt;_U2&gt;(__y)) { }

      template&lt;typename _U2, typename
	       enable_if&lt;_PCCP::template
			   _CopyMovePair&lt;false, _T1, _U2&gt;(),
                         bool&gt;::type=false&gt;
       explicit pair(const _T1&amp; __x, _U2&amp;&amp; __y)
       : first(__x), second(std::forward&lt;_U2&gt;(__y)) { }

      template&lt;typename _U1, typename _U2, typename
	       enable_if&lt;_PCCP::template
			   _MoveConstructiblePair&lt;_U1, _U2&gt;()
			  &amp;&amp; _PCCP::template
			   _ImplicitlyMoveConvertiblePair&lt;_U1, _U2&gt;(),
                         bool&gt;::type=true&gt;
	constexpr pair(_U1&amp;&amp; __x, _U2&amp;&amp; __y)
	: first(std::forward&lt;_U1&gt;(__x)), second(std::forward&lt;_U2&gt;(__y)) { }

      template&lt;typename _U1, typename _U2, typename
	       enable_if&lt;_PCCP::template
			   _MoveConstructiblePair&lt;_U1, _U2&gt;()
			  &amp;&amp; !_PCCP::template
			   _ImplicitlyMoveConvertiblePair&lt;_U1, _U2&gt;(),
                         bool&gt;::type=false&gt;
	explicit constexpr pair(_U1&amp;&amp; __x, _U2&amp;&amp; __y)
	: first(std::forward&lt;_U1&gt;(__x)), second(std::forward&lt;_U2&gt;(__y)) { }


      template&lt;typename _U1, typename _U2, typename
	       enable_if&lt;_PCCFP&lt;_U1, _U2&gt;::template
			   _MoveConstructiblePair&lt;_U1, _U2&gt;()
			  &amp;&amp; _PCCFP&lt;_U1, _U2&gt;::template
			   _ImplicitlyMoveConvertiblePair&lt;_U1, _U2&gt;(),
                         bool&gt;::type=true&gt;
	constexpr pair(pair&lt;_U1, _U2&gt;&amp;&amp; __p)
	: first(std::forward&lt;_U1&gt;(__p.first)),
	  second(std::forward&lt;_U2&gt;(__p.second)) { }

      template&lt;typename _U1, typename _U2, typename
	       enable_if&lt;_PCCFP&lt;_U1, _U2&gt;::template
			   _MoveConstructiblePair&lt;_U1, _U2&gt;()
			  &amp;&amp; !_PCCFP&lt;_U1, _U2&gt;::template
			   _ImplicitlyMoveConvertiblePair&lt;_U1, _U2&gt;(),
                         bool&gt;::type=false&gt;
	explicit constexpr pair(pair&lt;_U1, _U2&gt;&amp;&amp; __p)
	: first(std::forward&lt;_U1&gt;(__p.first)),
	  second(std::forward&lt;_U2&gt;(__p.second)) { }

      template&lt;typename... _Args1, typename... _Args2&gt;
        pair(piecewise_construct_t, tuple&lt;_Args1...&gt;, tuple&lt;_Args2...&gt;);

      pair&amp;
      operator=(typename conditional&lt;
		__and_&lt;is_copy_assignable&lt;_T1&gt;,
		       is_copy_assignable&lt;_T2&gt;&gt;::value,
		const pair&amp;, const __nonesuch_no_braces&amp;&gt;::type __p)
      {
	first = __p.first;
	second = __p.second;
	return *this;
      }

      pair&amp;
      operator=(typename conditional&lt;
		__and_&lt;is_move_assignable&lt;_T1&gt;,
		       is_move_assignable&lt;_T2&gt;&gt;::value,
		pair&amp;&amp;, __nonesuch_no_braces&amp;&amp;&gt;::type __p)
      noexcept(__and_&lt;is_nothrow_move_assignable&lt;_T1&gt;,
		      is_nothrow_move_assignable&lt;_T2&gt;&gt;::value)
      {
	first = std::forward&lt;first_type&gt;(__p.first);
	second = std::forward&lt;second_type&gt;(__p.second);
	return *this;
      }

      template&lt;typename _U1, typename _U2&gt;
      typename enable_if&lt;__and_&lt;is_assignable&lt;_T1&amp;, const _U1&amp;&gt;,
				is_assignable&lt;_T2&amp;, const _U2&amp;&gt;&gt;::value,
			 pair&amp;&gt;::type
	operator=(const pair&lt;_U1, _U2&gt;&amp; __p)
	{
	  first = __p.first;
	  second = __p.second;
	  return *this;
	}

      template&lt;typename _U1, typename _U2&gt;
      typename enable_if&lt;__and_&lt;is_assignable&lt;_T1&amp;, _U1&amp;&amp;&gt;,
				is_assignable&lt;_T2&amp;, _U2&amp;&amp;&gt;&gt;::value,
			 pair&amp;&gt;::type
	operator=(pair&lt;_U1, _U2&gt;&amp;&amp; __p)
	{
	  first = std::forward&lt;_U1&gt;(__p.first);
	  second = std::forward&lt;_U2&gt;(__p.second);
	  return *this;
	}

      void
      swap(pair&amp; __p)
      noexcept(__and_&lt;__is_nothrow_swappable&lt;_T1&gt;,
                      __is_nothrow_swappable&lt;_T2&gt;&gt;::value)
      {
	using std::swap;
	swap(first, __p.first);
	swap(second, __p.second);
      }

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

#if __cpp_deduction_guides &gt;= 201606
  template&lt;typename _T1, typename _T2&gt; pair(_T1, _T2) -&gt; pair&lt;_T1, _T2&gt;;
#endif

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

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

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

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

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

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

#if __cplusplus &gt;= 201103L
  /// See std::pair::swap().
  // Note:  no std::swap overloads in C++03 mode, this has performance
  //        implications, see, eg, libstdc++/38466.
  template&lt;typename _T1, typename _T2&gt;
    inline
#if __cplusplus &gt; 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
    // Constrained free swap overload, see p0185r1
    typename enable_if&lt;__and_&lt;__is_swappable&lt;_T1&gt;,
                              __is_swappable&lt;_T2&gt;&gt;::value&gt;::type
#else
    void
#endif
    swap(pair&lt;_T1, _T2&gt;&amp; __x, pair&lt;_T1, _T2&gt;&amp; __y)
    noexcept(noexcept(__x.swap(__y)))
    { __x.swap(__y); }

#if __cplusplus &gt; 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
  template&lt;typename _T1, typename _T2&gt;
    typename enable_if&lt;!__and_&lt;__is_swappable&lt;_T1&gt;,
			       __is_swappable&lt;_T2&gt;&gt;::value&gt;::type
    swap(pair&lt;_T1, _T2&gt;&amp;, pair&lt;_T1, _T2&gt;&amp;) = delete;
#endif
#endif // __cplusplus &gt;= 201103L

  /**
   *  @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&lt;&gt; 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 &gt;= 201103L
  // NB: DR 706.
  template&lt;typename _T1, typename _T2&gt;
    constexpr pair&lt;typename __decay_and_strip&lt;_T1&gt;::__type,
                   typename __decay_and_strip&lt;_T2&gt;::__type&gt;
    make_pair(_T1&amp;&amp; __x, _T2&amp;&amp; __y)
    {
      typedef typename __decay_and_strip&lt;_T1&gt;::__type __ds_type1;
      typedef typename __decay_and_strip&lt;_T2&gt;::__type __ds_type2;
      typedef pair&lt;__ds_type1, __ds_type2&gt; 	      __pair_type;
      return __pair_type(std::forward&lt;_T1&gt;(__x), std::forward&lt;_T2&gt;(__y));
    }
#else
  template&lt;typename _T1, typename _T2&gt;
    inline pair&lt;_T1, _T2&gt;
    make_pair(_T1 __x, _T2 __y)
    { return pair&lt;_T1, _T2&gt;(__x, __y); }
#endif

  /// @}

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#endif /* _STL_PAIR_H */
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