libstdc++-v3/include/experimental/array

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

// Copyright (C) 2015-2025 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/array
 *  This is a TS C++ Library header.
 *  @ingroup libfund-ts
 */

#ifndef _GLIBCXX_EXPERIMENTAL_ARRAY
#define _GLIBCXX_EXPERIMENTAL_ARRAY 1

#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif

#include <bits/requires_hosted.h> // experimental is currently omitted

#if __cplusplus >= 201402L

#include <array>
#include <experimental/type_traits>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

namespace experimental
{
inline namespace fundamentals_v2
{
#define __cpp_lib_experimental_make_array 201505
  /**
   * @defgroup make_array Array creation functions
   * @ingroup libfund-ts
   *
   * Array creation functions as described in N4529,
   * Working Draft, C++ Extensions for Library Fundamentals, Version 2
   *
   * @{
   */

template<typename _Dest, typename... _Types>
  struct __make_array_elem
  {
    using type = _Dest;
  };

template<typename... _Types>
  struct __make_array_elem<void, _Types...>
  : common_type<_Types...>
  {
    template <typename>
      struct __is_reference_wrapper : false_type
      {};

    template <typename _Up>
      struct __is_reference_wrapper<reference_wrapper<_Up>> : true_type
      {};

    static_assert(!__or_<__is_reference_wrapper<decay_t<_Types>>...>::value,
                  "make_array must be used with an explicit target type when"
                  "any of the arguments is a reference_wrapper");
  };

/// Create a std::array from a variable-length list of arguments.
template <typename _Dest = void, typename... _Types>
  constexpr
  array<typename __make_array_elem<_Dest, _Types...>::type, sizeof...(_Types)>
  make_array(_Types&&... __t)
  {
    return {{ std::forward<_Types>(__t)... }};
  }

template <typename _Tp, size_t _Nm, size_t... _Idx>
  constexpr array<remove_cv_t<_Tp>, _Nm>
  __to_array(_Tp (&__a)[_Nm], index_sequence<_Idx...>)
  {
    return {{__a[_Idx]...}};
  }

/// Create a std::array from an array.
template <typename _Tp, size_t _Nm>
  constexpr array<remove_cv_t<_Tp>, _Nm>
  to_array(_Tp (&__a)[_Nm])
  noexcept(is_nothrow_constructible<remove_cv_t<_Tp>, _Tp&>::value)
  {
    return experimental::__to_array(__a, make_index_sequence<_Nm>{});
  }

  /// @} group make_array
} // namespace fundamentals_v2
} // namespace experimental

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#endif // C++14

#endif // _GLIBCXX_EXPERIMENTAL_ARRAY