libstdc++-v3/include/std/utility - gcc - Git at Google

 // <utility> -*- C++ -*-

 // Copyright (C) 2001-2021 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 include/utility
  *  This is a Standard C++ Library header.
  */

 #ifndef _GLIBCXX_UTILITY
 #define _GLIBCXX_UTILITY 1

 #pragma GCC system_header

 /**
  * @defgroup utilities Utilities
  *
  * Components deemed generally useful. Includes pair, tuple,
  * forward/move helpers, ratio, function object, metaprogramming and
  * type traits, time, date, and memory functions.
  */

 #include <bits/c++config.h>
 #include <bits/stl_relops.h>
 #include <bits/stl_pair.h>

 #if __cplusplus >= 201103L

 #include <type_traits>
 #include <bits/move.h>
 #include <initializer_list>

 #if __cplusplus > 201703L
 #include <ext/numeric_traits.h>
 #endif

 namespace std _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION

   /// Finds the size of a given tuple type.
   template<typename _Tp>
     struct tuple_size;

   // _GLIBCXX_RESOLVE_LIB_DEFECTS
   // 2313. tuple_size should always derive from integral_constant<size_t, N>
   // 2770. tuple_size<const T> specialization is not SFINAE compatible

   template<typename _Tp,
 	   typename _Up = typename remove_cv<_Tp>::type,
 	   typename = typename enable_if<is_same<_Tp, _Up>::value>::type,
 	   size_t = tuple_size<_Tp>::value>
     using __enable_if_has_tuple_size = _Tp;

   template<typename _Tp>
     struct tuple_size<const __enable_if_has_tuple_size<_Tp>>
     : public tuple_size<_Tp> { };

   template<typename _Tp>
     struct tuple_size<volatile __enable_if_has_tuple_size<_Tp>>
     : public tuple_size<_Tp> { };

   template<typename _Tp>
     struct tuple_size<const volatile __enable_if_has_tuple_size<_Tp>>
     : public tuple_size<_Tp> { };

   /// Gives the type of the ith element of a given tuple type.
   template<size_t __i, typename _Tp>
     struct tuple_element;

   // Duplicate of C++14's tuple_element_t for internal use in C++11 mode
   template<size_t __i, typename _Tp>
     using __tuple_element_t = typename tuple_element<__i, _Tp>::type;

   template<size_t __i, typename _Tp>
     struct tuple_element<__i, const _Tp>
     {
       typedef typename add_const<__tuple_element_t<__i, _Tp>>::type type;
     };

   template<size_t __i, typename _Tp>
     struct tuple_element<__i, volatile _Tp>
     {
       typedef typename add_volatile<__tuple_element_t<__i, _Tp>>::type type;
     };

   template<size_t __i, typename _Tp>
     struct tuple_element<__i, const volatile _Tp>
     {
       typedef typename add_cv<__tuple_element_t<__i, _Tp>>::type type;
     };

 #if __cplusplus >= 201402L
 // The standard says this macro and alias template should be in <tuple>
 // but we define them here, to be available when the partial specializations
 // of tuple_element<pair<T,U>> and tuple_element<array<T,N>> are defined.
 #define __cpp_lib_tuple_element_t 201402L

   template<size_t __i, typename _Tp>
     using tuple_element_t = typename tuple_element<__i, _Tp>::type;
 #endif

   // Various functions which give std::pair a tuple-like interface.

   /// Partial specialization for std::pair
   template<typename _T1, typename _T2>
     struct __is_tuple_like_impl<pair<_T1, _T2>> : true_type
     { };

   /// Partial specialization for std::pair
   template<class _Tp1, class _Tp2>
     struct tuple_size<pair<_Tp1, _Tp2>>
     : public integral_constant<size_t, 2> { };

   /// Partial specialization for std::pair
   template<class _Tp1, class _Tp2>
     struct tuple_element<0, pair<_Tp1, _Tp2>>
     { typedef _Tp1 type; };

   /// Partial specialization for std::pair
   template<class _Tp1, class _Tp2>
     struct tuple_element<1, pair<_Tp1, _Tp2>>
     { typedef _Tp2 type; };

   template<size_t _Int>
     struct __pair_get;

   template<>
     struct __pair_get<0>
     {
       template<typename _Tp1, typename _Tp2>
 	static constexpr _Tp1&
 	__get(pair<_Tp1, _Tp2>& __pair) noexcept
 	{ return __pair.first; }

       template<typename _Tp1, typename _Tp2>
 	static constexpr _Tp1&&
 	__move_get(pair<_Tp1, _Tp2>&& __pair) noexcept
 	{ return std::forward<_Tp1>(__pair.first); }

       template<typename _Tp1, typename _Tp2>
 	static constexpr const _Tp1&
 	__const_get(const pair<_Tp1, _Tp2>& __pair) noexcept
 	{ return __pair.first; }

       template<typename _Tp1, typename _Tp2>
 	static constexpr const _Tp1&&
 	__const_move_get(const pair<_Tp1, _Tp2>&& __pair) noexcept
 	{ return std::forward<const _Tp1>(__pair.first); }
     };

   template<>
     struct __pair_get<1>
     {
       template<typename _Tp1, typename _Tp2>
 	static constexpr _Tp2&
 	__get(pair<_Tp1, _Tp2>& __pair) noexcept
 	{ return __pair.second; }

       template<typename _Tp1, typename _Tp2>
 	static constexpr _Tp2&&
 	__move_get(pair<_Tp1, _Tp2>&& __pair) noexcept
 	{ return std::forward<_Tp2>(__pair.second); }

       template<typename _Tp1, typename _Tp2>
 	static constexpr const _Tp2&
 	__const_get(const pair<_Tp1, _Tp2>& __pair) noexcept
 	{ return __pair.second; }

       template<typename _Tp1, typename _Tp2>
 	static constexpr const _Tp2&&
 	__const_move_get(const pair<_Tp1, _Tp2>&& __pair) noexcept
 	{ return std::forward<const _Tp2>(__pair.second); }
     };

   template<size_t _Int, class _Tp1, class _Tp2>
     constexpr typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&
     get(pair<_Tp1, _Tp2>& __in) noexcept
     { return __pair_get<_Int>::__get(__in); }

   template<size_t _Int, class _Tp1, class _Tp2>
     constexpr typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&&
     get(pair<_Tp1, _Tp2>&& __in) noexcept
     { return __pair_get<_Int>::__move_get(std::move(__in)); }

   template<size_t _Int, class _Tp1, class _Tp2>
     constexpr const typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&
     get(const pair<_Tp1, _Tp2>& __in) noexcept
     { return __pair_get<_Int>::__const_get(__in); }

   template<size_t _Int, class _Tp1, class _Tp2>
     constexpr const typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&&
     get(const pair<_Tp1, _Tp2>&& __in) noexcept
     { return __pair_get<_Int>::__const_move_get(std::move(__in)); }

 #if __cplusplus >= 201402L

 #define __cpp_lib_tuples_by_type 201304

   template <typename _Tp, typename _Up>
     constexpr _Tp&
     get(pair<_Tp, _Up>& __p) noexcept
     { return __p.first; }

   template <typename _Tp, typename _Up>
     constexpr const _Tp&
     get(const pair<_Tp, _Up>& __p) noexcept
     { return __p.first; }

   template <typename _Tp, typename _Up>
     constexpr _Tp&&
     get(pair<_Tp, _Up>&& __p) noexcept
     { return std::move(__p.first); }

   template <typename _Tp, typename _Up>
     constexpr const _Tp&&
     get(const pair<_Tp, _Up>&& __p) noexcept
     { return std::move(__p.first); }

   template <typename _Tp, typename _Up>
     constexpr _Tp&
     get(pair<_Up, _Tp>& __p) noexcept
     { return __p.second; }

   template <typename _Tp, typename _Up>
     constexpr const _Tp&
     get(const pair<_Up, _Tp>& __p) noexcept
     { return __p.second; }

   template <typename _Tp, typename _Up>
     constexpr _Tp&&
     get(pair<_Up, _Tp>&& __p) noexcept
     { return std::move(__p.second); }

   template <typename _Tp, typename _Up>
     constexpr const _Tp&&
     get(const pair<_Up, _Tp>&& __p) noexcept
     { return std::move(__p.second); }

 #define __cpp_lib_exchange_function 201304

   /// Assign @p __new_val to @p __obj and return its previous value.
   template <typename _Tp, typename _Up = _Tp>
     _GLIBCXX20_CONSTEXPR
     inline _Tp
     exchange(_Tp& __obj, _Up&& __new_val)
     { return std::__exchange(__obj, std::forward<_Up>(__new_val)); }

 #endif // C++14

   // Stores a tuple of indices.  Used by tuple and pair, and by bind() to
   // extract the elements in a tuple.
   template<size_t... _Indexes> struct _Index_tuple { };

   // Builds an _Index_tuple<0, 1, 2, ..., _Num-1>.
   template<size_t _Num>
     struct _Build_index_tuple
     {
 #if __has_builtin(__make_integer_seq)
       template<typename, size_t... _Indices>
         using _IdxTuple = _Index_tuple<_Indices...>;

       // Clang defines __make_integer_seq for this purpose.
       using __type = __make_integer_seq<_IdxTuple, size_t, _Num>;
 #else
       // For GCC and other compilers, use __integer_pack instead.
       using __type = _Index_tuple<__integer_pack(_Num)...>;
 #endif
     };

 #if __cplusplus >= 201402L

 #define __cpp_lib_integer_sequence 201304

   /// Class template integer_sequence
   template<typename _Tp, _Tp... _Idx>
     struct integer_sequence
     {
       typedef _Tp value_type;
       static constexpr size_t size() noexcept { return sizeof...(_Idx); }
     };

   /// Alias template make_integer_sequence
   template<typename _Tp, _Tp _Num>
     using make_integer_sequence
 #if __has_builtin(__make_integer_seq)
       = __make_integer_seq<integer_sequence, _Tp, _Num>;
 #else
       = integer_sequence<_Tp, __integer_pack(_Num)...>;
 #endif

   /// Alias template index_sequence
   template<size_t... _Idx>
     using index_sequence = integer_sequence<size_t, _Idx...>;

   /// Alias template make_index_sequence
   template<size_t _Num>
     using make_index_sequence = make_integer_sequence<size_t, _Num>;

   /// Alias template index_sequence_for
   template<typename... _Types>
     using index_sequence_for = make_index_sequence<sizeof...(_Types)>;
 #endif

 #if __cplusplus > 201402L

   struct in_place_t {
     explicit in_place_t() = default;
   };

   inline constexpr in_place_t in_place{};

   template<typename _Tp> struct in_place_type_t
   {
     explicit in_place_type_t() = default;
   };

   template<typename _Tp>
     inline constexpr in_place_type_t<_Tp> in_place_type{};

   template<size_t _Idx> struct in_place_index_t
   {
     explicit in_place_index_t() = default;
   };

   template<size_t _Idx>
     inline constexpr in_place_index_t<_Idx> in_place_index{};

   template<typename>
     struct __is_in_place_type_impl : false_type
     { };

   template<typename _Tp>
     struct __is_in_place_type_impl<in_place_type_t<_Tp>> : true_type
     { };

   template<typename _Tp>
     struct __is_in_place_type
       : public __is_in_place_type_impl<_Tp>
     { };

 #define  __cpp_lib_as_const 201510
   template<typename _Tp>
     [[nodiscard]]
     constexpr add_const_t<_Tp>&
     as_const(_Tp& __t) noexcept
     { return __t; }

   template<typename _Tp>
     void as_const(const _Tp&&) = delete;

 #if __cplusplus > 201703L
 #define __cpp_lib_integer_comparison_functions 202002L

   template<typename _Tp, typename _Up>
     constexpr bool
     cmp_equal(_Tp __t, _Up __u) noexcept
     {
       static_assert(__is_standard_integer<_Tp>::value);
       static_assert(__is_standard_integer<_Up>::value);

       if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
 	return __t == __u;
       else if constexpr (is_signed_v<_Tp>)
 	return __t >= 0 && make_unsigned_t<_Tp>(__t) == __u;
       else
 	return __u >= 0 && __t == make_unsigned_t<_Up>(__u);
     }

   template<typename _Tp, typename _Up>
     constexpr bool
     cmp_not_equal(_Tp __t, _Up __u) noexcept
     { return !std::cmp_equal(__t, __u); }

   template<typename _Tp, typename _Up>
     constexpr bool
     cmp_less(_Tp __t, _Up __u) noexcept
     {
       static_assert(__is_standard_integer<_Tp>::value);
       static_assert(__is_standard_integer<_Up>::value);

       if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
 	return __t < __u;
       else if constexpr (is_signed_v<_Tp>)
 	return __t < 0 || make_unsigned_t<_Tp>(__t) < __u;
       else
 	return __u >= 0 && __t < make_unsigned_t<_Up>(__u);
     }

   template<typename _Tp, typename _Up>
     constexpr bool
     cmp_greater(_Tp __t, _Up __u) noexcept
     { return std::cmp_less(__u, __t); }

   template<typename _Tp, typename _Up>
     constexpr bool
     cmp_less_equal(_Tp __t, _Up __u) noexcept
     { return !std::cmp_less(__u, __t); }

   template<typename _Tp, typename _Up>
     constexpr bool
     cmp_greater_equal(_Tp __t, _Up __u) noexcept
     { return !std::cmp_less(__t, __u); }

   template<typename _Up, typename _Tp>
     constexpr bool
     in_range(_Tp __t) noexcept
     {
       static_assert(__is_standard_integer<_Up>::value);
       static_assert(__is_standard_integer<_Tp>::value);
       using __gnu_cxx::__int_traits;

       if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
 	return __int_traits<_Up>::__min <= __t
 	  && __t <= __int_traits<_Up>::__max;
       else if constexpr (is_signed_v<_Tp>)
 	return __t >= 0
 	  && make_unsigned_t<_Tp>(__t) <= __int_traits<_Up>::__max;
       else
 	return __t <= make_unsigned_t<_Up>(__int_traits<_Up>::__max);
     }

 #if __cplusplus > 202002L
 #define __cpp_lib_to_underlying 202102L
   /// Convert an object of enumeration type to its underlying type.
   template<typename _Tp>
     [[nodiscard]]
     constexpr underlying_type_t<_Tp>
     to_underlying(_Tp __value) noexcept
     { return static_cast<underlying_type_t<_Tp>>(__value); }
 #endif // C++23
 #endif // C++20
 #endif // C++17

 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace

 #endif

 #endif /* _GLIBCXX_UTILITY */
	// <utility> -- C++ --

	// Copyright (C) 2001-2021 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 include/utility
	* This is a Standard C++ Library header.
	*/

	#ifndef _GLIBCXX_UTILITY
	#define _GLIBCXX_UTILITY 1

	#pragma GCC system_header

	/**
	* @defgroup utilities Utilities
	*
	* Components deemed generally useful. Includes pair, tuple,
	* forward/move helpers, ratio, function object, metaprogramming and
	* type traits, time, date, and memory functions.
	*/

	#include <bits/c++config.h>
	#include <bits/stl_relops.h>
	#include <bits/stl_pair.h>

	#if __cplusplus >= 201103L

	#include <type_traits>
	#include <bits/move.h>
	#include <initializer_list>

	#if __cplusplus > 201703L
	#include <ext/numeric_traits.h>
	#endif

	namespace std _GLIBCXX_VISIBILITY(default)
	{
	_GLIBCXX_BEGIN_NAMESPACE_VERSION

	/// Finds the size of a given tuple type.
	template<typename _Tp>
	struct tuple_size;

	// _GLIBCXX_RESOLVE_LIB_DEFECTS
	// 2313. tuple_size should always derive from integral_constant<size_t, N>
	// 2770. tuple_size<const T> specialization is not SFINAE compatible

	template<typename _Tp,
	typename _Up = typename remove_cv<_Tp>::type,
	typename = typename enable_if<is_same<_Tp, _Up>::value>::type,
	size_t = tuple_size<_Tp>::value>
	using __enable_if_has_tuple_size = _Tp;

	template<typename _Tp>
	struct tuple_size<const __enable_if_has_tuple_size<_Tp>>
	: public tuple_size<_Tp> { };

	template<typename _Tp>
	struct tuple_size<volatile __enable_if_has_tuple_size<_Tp>>
	: public tuple_size<_Tp> { };

	template<typename _Tp>
	struct tuple_size<const volatile __enable_if_has_tuple_size<_Tp>>
	: public tuple_size<_Tp> { };

	/// Gives the type of the ith element of a given tuple type.
	template<size_t __i, typename _Tp>
	struct tuple_element;

	// Duplicate of C++14's tuple_element_t for internal use in C++11 mode
	template<size_t __i, typename _Tp>
	using __tuple_element_t = typename tuple_element<__i, _Tp>::type;

	template<size_t __i, typename _Tp>
	struct tuple_element<__i, const _Tp>
	{
	typedef typename add_const<__tuple_element_t<__i, _Tp>>::type type;
	};

	template<size_t __i, typename _Tp>
	struct tuple_element<__i, volatile _Tp>
	{
	typedef typename add_volatile<__tuple_element_t<__i, _Tp>>::type type;
	};

	template<size_t __i, typename _Tp>
	struct tuple_element<__i, const volatile _Tp>
	{
	typedef typename add_cv<__tuple_element_t<__i, _Tp>>::type type;
	};

	#if __cplusplus >= 201402L
	// The standard says this macro and alias template should be in <tuple>
	// but we define them here, to be available when the partial specializations
	// of tuple_element<pair<T,U>> and tuple_element<array<T,N>> are defined.
	#define __cpp_lib_tuple_element_t 201402L

	template<size_t __i, typename _Tp>
	using tuple_element_t = typename tuple_element<__i, _Tp>::type;
	#endif

	// Various functions which give std::pair a tuple-like interface.

	/// Partial specialization for std::pair
	template<typename _T1, typename _T2>
	struct __is_tuple_like_impl<pair<_T1, _T2>> : true_type
	{ };

	/// Partial specialization for std::pair
	template<class _Tp1, class _Tp2>
	struct tuple_size<pair<_Tp1, _Tp2>>
	: public integral_constant<size_t, 2> { };

	/// Partial specialization for std::pair
	template<class _Tp1, class _Tp2>
	struct tuple_element<0, pair<_Tp1, _Tp2>>
	{ typedef _Tp1 type; };

	/// Partial specialization for std::pair
	template<class _Tp1, class _Tp2>
	struct tuple_element<1, pair<_Tp1, _Tp2>>
	{ typedef _Tp2 type; };

	template<size_t _Int>
	struct __pair_get;

	template<>
	struct __pair_get<0>
	{
	template<typename _Tp1, typename _Tp2>
	static constexpr _Tp1&
	__get(pair<_Tp1, _Tp2>& __pair) noexcept
	{ return __pair.first; }

	template<typename _Tp1, typename _Tp2>
	static constexpr _Tp1&&
	__move_get(pair<_Tp1, _Tp2>&& __pair) noexcept
	{ return std::forward<_Tp1>(__pair.first); }

	template<typename _Tp1, typename _Tp2>
	static constexpr const _Tp1&
	__const_get(const pair<_Tp1, _Tp2>& __pair) noexcept
	{ return __pair.first; }

	template<typename _Tp1, typename _Tp2>
	static constexpr const _Tp1&&
	__const_move_get(const pair<_Tp1, _Tp2>&& __pair) noexcept
	{ return std::forward<const _Tp1>(__pair.first); }
	};

	template<>
	struct __pair_get<1>
	{
	template<typename _Tp1, typename _Tp2>
	static constexpr _Tp2&
	__get(pair<_Tp1, _Tp2>& __pair) noexcept
	{ return __pair.second; }

	template<typename _Tp1, typename _Tp2>
	static constexpr _Tp2&&
	__move_get(pair<_Tp1, _Tp2>&& __pair) noexcept
	{ return std::forward<_Tp2>(__pair.second); }

	template<typename _Tp1, typename _Tp2>
	static constexpr const _Tp2&
	__const_get(const pair<_Tp1, _Tp2>& __pair) noexcept
	{ return __pair.second; }

	template<typename _Tp1, typename _Tp2>
	static constexpr const _Tp2&&
	__const_move_get(const pair<_Tp1, _Tp2>&& __pair) noexcept
	{ return std::forward<const _Tp2>(__pair.second); }
	};

	template<size_t _Int, class _Tp1, class _Tp2>
	constexpr typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&
	get(pair<_Tp1, _Tp2>& __in) noexcept
	{ return __pair_get<_Int>::__get(__in); }

	template<size_t _Int, class _Tp1, class _Tp2>
	constexpr typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&&
	get(pair<_Tp1, _Tp2>&& __in) noexcept
	{ return __pair_get<_Int>::__move_get(std::move(__in)); }

	template<size_t _Int, class _Tp1, class _Tp2>
	constexpr const typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&
	get(const pair<_Tp1, _Tp2>& __in) noexcept
	{ return __pair_get<_Int>::__const_get(__in); }

	template<size_t _Int, class _Tp1, class _Tp2>
	constexpr const typename tuple_element<_Int, pair<_Tp1, _Tp2>>::type&&
	get(const pair<_Tp1, _Tp2>&& __in) noexcept
	{ return __pair_get<_Int>::__const_move_get(std::move(__in)); }

	#if __cplusplus >= 201402L

	#define __cpp_lib_tuples_by_type 201304

	template <typename _Tp, typename _Up>
	constexpr _Tp&
	get(pair<_Tp, _Up>& __p) noexcept
	{ return __p.first; }

	template <typename _Tp, typename _Up>
	constexpr const _Tp&
	get(const pair<_Tp, _Up>& __p) noexcept
	{ return __p.first; }

	template <typename _Tp, typename _Up>
	constexpr _Tp&&
	get(pair<_Tp, _Up>&& __p) noexcept
	{ return std::move(__p.first); }

	template <typename _Tp, typename _Up>
	constexpr const _Tp&&
	get(const pair<_Tp, _Up>&& __p) noexcept
	{ return std::move(__p.first); }

	template <typename _Tp, typename _Up>
	constexpr _Tp&
	get(pair<_Up, _Tp>& __p) noexcept
	{ return __p.second; }

	template <typename _Tp, typename _Up>
	constexpr const _Tp&
	get(const pair<_Up, _Tp>& __p) noexcept
	{ return __p.second; }

	template <typename _Tp, typename _Up>
	constexpr _Tp&&
	get(pair<_Up, _Tp>&& __p) noexcept
	{ return std::move(__p.second); }

	template <typename _Tp, typename _Up>
	constexpr const _Tp&&
	get(const pair<_Up, _Tp>&& __p) noexcept
	{ return std::move(__p.second); }

	#define __cpp_lib_exchange_function 201304

	/// Assign @p __new_val to @p __obj and return its previous value.
	template <typename _Tp, typename _Up = _Tp>
	_GLIBCXX20_CONSTEXPR
	inline _Tp
	exchange(_Tp& __obj, _Up&& __new_val)
	{ return std::__exchange(__obj, std::forward<_Up>(__new_val)); }

	#endif // C++14

	// Stores a tuple of indices. Used by tuple and pair, and by bind() to
	// extract the elements in a tuple.
	template<size_t... _Indexes> struct _Index_tuple { };

	// Builds an _Index_tuple<0, 1, 2, ..., _Num-1>.
	template<size_t _Num>
	struct _Build_index_tuple
	{
	#if __has_builtin(__make_integer_seq)
	template<typename, size_t... _Indices>
	using _IdxTuple = _Index_tuple<_Indices...>;

	// Clang defines __make_integer_seq for this purpose.
	using __type = __make_integer_seq<_IdxTuple, size_t, _Num>;
	#else
	// For GCC and other compilers, use __integer_pack instead.
	using __type = _Index_tuple<__integer_pack(_Num)...>;
	#endif
	};

	#if __cplusplus >= 201402L

	#define __cpp_lib_integer_sequence 201304

	/// Class template integer_sequence
	template<typename _Tp, _Tp... _Idx>
	struct integer_sequence
	{
	typedef _Tp value_type;
	static constexpr size_t size() noexcept { return sizeof...(_Idx); }
	};

	/// Alias template make_integer_sequence
	template<typename _Tp, _Tp _Num>
	using make_integer_sequence
	#if __has_builtin(__make_integer_seq)
	= __make_integer_seq<integer_sequence, _Tp, _Num>;
	#else
	= integer_sequence<_Tp, __integer_pack(_Num)...>;
	#endif

	/// Alias template index_sequence
	template<size_t... _Idx>
	using index_sequence = integer_sequence<size_t, _Idx...>;

	/// Alias template make_index_sequence
	template<size_t _Num>
	using make_index_sequence = make_integer_sequence<size_t, _Num>;

	/// Alias template index_sequence_for
	template<typename... _Types>
	using index_sequence_for = make_index_sequence<sizeof...(_Types)>;
	#endif

	#if __cplusplus > 201402L

	struct in_place_t {
	explicit in_place_t() = default;
	};

	inline constexpr in_place_t in_place{};

	template<typename _Tp> struct in_place_type_t
	{
	explicit in_place_type_t() = default;
	};

	template<typename _Tp>
	inline constexpr in_place_type_t<_Tp> in_place_type{};

	template<size_t _Idx> struct in_place_index_t
	{
	explicit in_place_index_t() = default;
	};

	template<size_t _Idx>
	inline constexpr in_place_index_t<_Idx> in_place_index{};

	template<typename>
	struct __is_in_place_type_impl : false_type
	{ };

	template<typename _Tp>
	struct __is_in_place_type_impl<in_place_type_t<_Tp>> : true_type
	{ };

	template<typename _Tp>
	struct __is_in_place_type
	: public __is_in_place_type_impl<_Tp>
	{ };

	#define __cpp_lib_as_const 201510
	template<typename _Tp>
	[[nodiscard]]
	constexpr add_const_t<_Tp>&
	as_const(_Tp& __t) noexcept
	{ return __t; }

	template<typename _Tp>
	void as_const(const _Tp&&) = delete;

	#if __cplusplus > 201703L
	#define __cpp_lib_integer_comparison_functions 202002L

	template<typename _Tp, typename _Up>
	constexpr bool
	cmp_equal(_Tp __t, _Up __u) noexcept
	{
	static_assert(__is_standard_integer<_Tp>::value);
	static_assert(__is_standard_integer<_Up>::value);

	if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
	return __t == __u;
	else if constexpr (is_signed_v<_Tp>)
	return __t >= 0 && make_unsigned_t<_Tp>(__t) == __u;
	else
	return __u >= 0 && __t == make_unsigned_t<_Up>(__u);
	}

	template<typename _Tp, typename _Up>
	constexpr bool
	cmp_not_equal(_Tp __t, _Up __u) noexcept
	{ return !std::cmp_equal(__t, __u); }

	template<typename _Tp, typename _Up>
	constexpr bool
	cmp_less(_Tp __t, _Up __u) noexcept
	{
	static_assert(__is_standard_integer<_Tp>::value);
	static_assert(__is_standard_integer<_Up>::value);

	if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
	return __t < __u;
	else if constexpr (is_signed_v<_Tp>)
	return __t < 0 \|\| make_unsigned_t<_Tp>(__t) < __u;
	else
	return __u >= 0 && __t < make_unsigned_t<_Up>(__u);
	}

	template<typename _Tp, typename _Up>
	constexpr bool
	cmp_greater(_Tp __t, _Up __u) noexcept
	{ return std::cmp_less(__u, __t); }

	template<typename _Tp, typename _Up>
	constexpr bool
	cmp_less_equal(_Tp __t, _Up __u) noexcept
	{ return !std::cmp_less(__u, __t); }

	template<typename _Tp, typename _Up>
	constexpr bool
	cmp_greater_equal(_Tp __t, _Up __u) noexcept
	{ return !std::cmp_less(__t, __u); }

	template<typename _Up, typename _Tp>
	constexpr bool
	in_range(_Tp __t) noexcept
	{
	static_assert(__is_standard_integer<_Up>::value);
	static_assert(__is_standard_integer<_Tp>::value);
	using __gnu_cxx::__int_traits;

	if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
	return __int_traits<_Up>::__min <= __t
	&& __t <= __int_traits<_Up>::__max;
	else if constexpr (is_signed_v<_Tp>)
	return __t >= 0
	&& make_unsigned_t<_Tp>(__t) <= __int_traits<_Up>::__max;
	else
	return __t <= make_unsigned_t<_Up>(__int_traits<_Up>::__max);
	}

	#if __cplusplus > 202002L
	#define __cpp_lib_to_underlying 202102L
	/// Convert an object of enumeration type to its underlying type.
	template<typename _Tp>
	[[nodiscard]]
	constexpr underlying_type_t<_Tp>
	to_underlying(_Tp __value) noexcept
	{ return static_cast<underlying_type_t<_Tp>>(__value); }
	#endif // C++23
	#endif // C++20
	#endif // C++17

	_GLIBCXX_END_NAMESPACE_VERSION
	} // namespace

	#endif

	#endif /* _GLIBCXX_UTILITY */