libstdc++-v3/include/experimental/array

   1 // <experimental/array> -*- C++ -*-
   2
   3 // Copyright (C) 2015-2025 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 #ifdef _GLIBCXX_SYSHDR
  34 #pragma GCC system_header
  35 #endif
  36
  37 #include <bits/requires_hosted.h> // experimental is currently omitted
  38
  39 #if __cplusplus >= 201402L
  40
  41 #include <array>
  42 #include <experimental/type_traits>
  43
  44 namespace std _GLIBCXX_VISIBILITY(default)
  45 {
  46 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  47
  48 namespace experimental
  49 {
  50 inline namespace fundamentals_v2
  51 {
  52 #define __cpp_lib_experimental_make_array 201505
  53   /**
  54    * @defgroup make_array Array creation functions
  55    * @ingroup libfund-ts
  56    *
  57    * Array creation functions as described in N4529,
  58    * Working Draft, C++ Extensions for Library Fundamentals, Version 2
  59    *
  60    * @{
  61    */
  62
  63 template<typename _Dest, typename... _Types>
  64   struct __make_array_elem
  65   {
  66     using type = _Dest;
  67   };
  68
  69 template<typename... _Types>
  70   struct __make_array_elem<void, _Types...>
  71   : common_type<_Types...>
  72   {
  73     template <typename>
  74       struct __is_reference_wrapper : false_type
  75       {};
  76
  77     template <typename _Up>
  78       struct __is_reference_wrapper<reference_wrapper<_Up>> : true_type
  79       {};
  80
  81     static_assert(!__or_<__is_reference_wrapper<decay_t<_Types>>...>::value,
  82                   "make_array must be used with an explicit target type when"
  83                   "any of the arguments is a reference_wrapper");
  84   };
  85
  86 /// Create a std::array from a variable-length list of arguments.
  87 template <typename _Dest = void, typename... _Types>
  88   constexpr
  89   array<typename __make_array_elem<_Dest, _Types...>::type, sizeof...(_Types)>
  90   make_array(_Types&&... __t)
  91   {
  92     return {{ std::forward<_Types>(__t)... }};
  93   }
  94
  95 template <typename _Tp, size_t _Nm, size_t... _Idx>
  96   constexpr array<remove_cv_t<_Tp>, _Nm>
  97   __to_array(_Tp (&__a)[_Nm], index_sequence<_Idx...>)
  98   {
  99     return {{__a[_Idx]...}};
 100   }
 101
 102 /// Create a std::array from an array.
 103 template <typename _Tp, size_t _Nm>
 104   constexpr array<remove_cv_t<_Tp>, _Nm>
 105   to_array(_Tp (&__a)[_Nm])
 106   noexcept(is_nothrow_constructible<remove_cv_t<_Tp>, _Tp&>::value)
 107   {
 108     return experimental::__to_array(__a, make_index_sequence<_Nm>{});
 109   }
 110
 111   /// @} group make_array
 112 } // namespace fundamentals_v2
 113 } // namespace experimental
 114
 115 _GLIBCXX_END_NAMESPACE_VERSION
 116 } // namespace std
 117
 118 #endif // C++14
 119
 120 #endif // _GLIBCXX_EXPERIMENTAL_ARRAY