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      1 // <experimental/array> -*- C++ -*-
      2 
      3 // Copyright (C) 2015-2022 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 #if __cplusplus >= 201402L
     36 
     37 #include <array>
     38 #include <experimental/type_traits>
     39 
     40 namespace std _GLIBCXX_VISIBILITY(default)
     41 {
     42 _GLIBCXX_BEGIN_NAMESPACE_VERSION
     43 
     44 namespace experimental
     45 {
     46 inline namespace fundamentals_v2
     47 {
     48 #define __cpp_lib_experimental_make_array 201505
     49   /**
     50    * @defgroup make_array Array creation functions
     51    * @ingroup libfund-ts
     52    *
     53    * Array creation functions as described in N4529,
     54    * Working Draft, C++ Extensions for Library Fundamentals, Version 2
     55    *
     56    * @{
     57    */
     58 
     59 template<typename _Dest, typename... _Types>
     60   struct __make_array_elem
     61   {
     62     using type = _Dest;
     63   };
     64 
     65 template<typename... _Types>
     66   struct __make_array_elem<void, _Types...>
     67   : common_type<_Types...>
     68   {
     69     template <typename>
     70       struct __is_reference_wrapper : false_type
     71       {};
     72 
     73     template <typename _Up>
     74       struct __is_reference_wrapper<reference_wrapper<_Up>> : true_type
     75       {};
     76 
     77     static_assert(!__or_<__is_reference_wrapper<decay_t<_Types>>...>::value,
     78                   "make_array must be used with an explicit target type when"
     79                   "any of the arguments is a reference_wrapper");
     80   };
     81 
     82 /// Create a std::array from a variable-length list of arguments.
     83 template <typename _Dest = void, typename... _Types>
     84   constexpr
     85   array<typename __make_array_elem<_Dest, _Types...>::type, sizeof...(_Types)>
     86   make_array(_Types&&... __t)
     87   {
     88     return {{ std::forward<_Types>(__t)... }};
     89   }
     90 
     91 template <typename _Tp, size_t _Nm, size_t... _Idx>
     92   constexpr array<remove_cv_t<_Tp>, _Nm>
     93   __to_array(_Tp (&__a)[_Nm], index_sequence<_Idx...>)
     94   {
     95     return {{__a[_Idx]...}};
     96   }
     97 
     98 /// Create a std::array from an array.
     99 template <typename _Tp, size_t _Nm>
    100   constexpr array<remove_cv_t<_Tp>, _Nm>
    101   to_array(_Tp (&__a)[_Nm])
    102   noexcept(is_nothrow_constructible<remove_cv_t<_Tp>, _Tp&>::value)
    103   {
    104     return experimental::__to_array(__a, make_index_sequence<_Nm>{});
    105   }
    106 
    107   /// @} group make_array
    108 } // namespace fundamentals_v2
    109 } // namespace experimental
    110 
    111 _GLIBCXX_END_NAMESPACE_VERSION
    112 } // namespace std
    113 
    114 #endif // C++14
    115 
    116 #endif // _GLIBCXX_EXPERIMENTAL_ARRAY
    117