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      1 // <experimental/array> -*- C++ -*-
      2 
      3 // Copyright (C) 2015-2024 Free Software Foundation, Inc.
      4 //
      5 // This file is part of the GNU ISO C++ Library.  This library is free
      6 // software; you can redistribute it and/or modify it under the
      7 // terms of the GNU General Public License as published by the
      8 // Free Software Foundation; either version 3, or (at your option)
      9 // any later version.
     10 
     11 // This library is distributed in the hope that it will be useful,
     12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
     13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     14 // GNU General Public License for more details.
     15 
     16 // Under Section 7 of GPL version 3, you are granted additional
     17 // permissions described in the GCC Runtime Library Exception, version
     18 // 3.1, as published by the Free Software Foundation.
     19 
     20 // You should have received a copy of the GNU General Public License and
     21 // a copy of the GCC Runtime Library Exception along with this program;
     22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
     23 // <http://www.gnu.org/licenses/>.
     24 
     25 /** @file experimental/array
     26  *  This is a TS C++ Library header.
     27  *  @ingroup libfund-ts
     28  */
     29 
     30 #ifndef _GLIBCXX_EXPERIMENTAL_ARRAY
     31 #define _GLIBCXX_EXPERIMENTAL_ARRAY 1
     32 
     33 #pragma GCC system_header
     34 
     35 #include <bits/requires_hosted.h> // experimental is currently omitted
     36 
     37 #if __cplusplus >= 201402L
     38 
     39 #include <array>
     40 #include <experimental/type_traits>
     41 
     42 namespace std _GLIBCXX_VISIBILITY(default)
     43 {
     44 _GLIBCXX_BEGIN_NAMESPACE_VERSION
     45 
     46 namespace experimental
     47 {
     48 inline namespace fundamentals_v2
     49 {
     50 #define __cpp_lib_experimental_make_array 201505
     51   /**
     52    * @defgroup make_array Array creation functions
     53    * @ingroup libfund-ts
     54    *
     55    * Array creation functions as described in N4529,
     56    * Working Draft, C++ Extensions for Library Fundamentals, Version 2
     57    *
     58    * @{
     59    */
     60 
     61 template<typename _Dest, typename... _Types>
     62   struct __make_array_elem
     63   {
     64     using type = _Dest;
     65   };
     66 
     67 template<typename... _Types>
     68   struct __make_array_elem<void, _Types...>
     69   : common_type<_Types...>
     70   {
     71     template <typename>
     72       struct __is_reference_wrapper : false_type
     73       {};
     74 
     75     template <typename _Up>
     76       struct __is_reference_wrapper<reference_wrapper<_Up>> : true_type
     77       {};
     78 
     79     static_assert(!__or_<__is_reference_wrapper<decay_t<_Types>>...>::value,
     80                   "make_array must be used with an explicit target type when"
     81                   "any of the arguments is a reference_wrapper");
     82   };
     83 
     84 /// Create a std::array from a variable-length list of arguments.
     85 template <typename _Dest = void, typename... _Types>
     86   constexpr
     87   array<typename __make_array_elem<_Dest, _Types...>::type, sizeof...(_Types)>
     88   make_array(_Types&&... __t)
     89   {
     90     return {{ std::forward<_Types>(__t)... }};
     91   }
     92 
     93 template <typename _Tp, size_t _Nm, size_t... _Idx>
     94   constexpr array<remove_cv_t<_Tp>, _Nm>
     95   __to_array(_Tp (&__a)[_Nm], index_sequence<_Idx...>)
     96   {
     97     return {{__a[_Idx]...}};
     98   }
     99 
    100 /// Create a std::array from an array.
    101 template <typename _Tp, size_t _Nm>
    102   constexpr array<remove_cv_t<_Tp>, _Nm>
    103   to_array(_Tp (&__a)[_Nm])
    104   noexcept(is_nothrow_constructible<remove_cv_t<_Tp>, _Tp&>::value)
    105   {
    106     return experimental::__to_array(__a, make_index_sequence<_Nm>{});
    107   }
    108 
    109   /// @} group make_array
    110 } // namespace fundamentals_v2
    111 } // namespace experimental
    112 
    113 _GLIBCXX_END_NAMESPACE_VERSION
    114 } // namespace std
    115 
    116 #endif // C++14
    117 
    118 #endif // _GLIBCXX_EXPERIMENTAL_ARRAY
    119