gcc/libstdc++-v3/include/experimental/tuple

// <experimental/tuple> -*- C++ -*-

// Copyright (C) 2014-2020 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/>.

/** @file experimental/tuple
 *  This is a TS C++ Library header.
 *  @ingroup libfund-ts
 */

#ifndef _GLIBCXX_EXPERIMENTAL_TUPLE
#define _GLIBCXX_EXPERIMENTAL_TUPLE 1

#pragma GCC system_header

#if __cplusplus >= 201402L

#include <tuple>
#include <bits/invoke.h>
#include <experimental/bits/lfts_config.h>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

namespace experimental
{
inline namespace fundamentals_v1
{
  // See C++14 20.4.2.5, tuple helper classes
  template <typename _Tp>
    constexpr size_t tuple_size_v = tuple_size<_Tp>::value;

#define __cpp_lib_experimental_tuple 201402

  template <typename _Fn, typename _Tuple, std::size_t... _Idx>
    constexpr decltype(auto)
    __apply_impl(_Fn&& __f, _Tuple&& __t, std::index_sequence<_Idx...>)
    {
      return std::__invoke(std::forward<_Fn>(__f),
			   std::get<_Idx>(std::forward<_Tuple>(__t))...);
    }

  template <typename _Fn, typename _Tuple>
    constexpr decltype(auto)
    apply(_Fn&& __f, _Tuple&& __t)
    {
      using _Indices =
	std::make_index_sequence<tuple_size_v<std::decay_t<_Tuple>>>;
      return experimental::__apply_impl(std::forward<_Fn>(__f),
					std::forward<_Tuple>(__t),
					_Indices{});
    }
} // namespace fundamentals_v1
} // namespace experimental

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#endif // C++14

#endif // _GLIBCXX_EXPERIMENTAL_TUPLE