libcxx/include/__utility/in_place.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef _LIBCPP___UTILITY_IN_PLACE_H
  10 #define _LIBCPP___UTILITY_IN_PLACE_H
  11
  12 #include <__config>
  13 #include <__type_traits/remove_cvref.h>
  14 #include <cstddef>
  15
  16 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  17 #  pragma GCC system_header
  18 #endif
  19
  20 _LIBCPP_BEGIN_NAMESPACE_STD
  21
  22 #if _LIBCPP_STD_VER >= 17
  23
  24 struct _LIBCPP_EXPORTED_FROM_ABI in_place_t {
  25   explicit in_place_t() = default;
  26 };
  27 inline constexpr in_place_t in_place{};
  28
  29 template <class _Tp>
  30 struct _LIBCPP_TEMPLATE_VIS in_place_type_t {
  31   _LIBCPP_HIDE_FROM_ABI explicit in_place_type_t() = default;
  32 };
  33 template <class _Tp>
  34 inline constexpr in_place_type_t<_Tp> in_place_type{};
  35
  36 template <size_t _Idx>
  37 struct _LIBCPP_TEMPLATE_VIS in_place_index_t {
  38   _LIBCPP_HIDE_FROM_ABI explicit in_place_index_t() = default;
  39 };
  40 template <size_t _Idx>
  41 inline constexpr in_place_index_t<_Idx> in_place_index{};
  42
  43 template <class _Tp> struct __is_inplace_type_imp : false_type {};
  44 template <class _Tp> struct __is_inplace_type_imp<in_place_type_t<_Tp>> : true_type {};
  45
  46 template <class _Tp>
  47 using __is_inplace_type = __is_inplace_type_imp<__remove_cvref_t<_Tp>>;
  48
  49 template <class _Tp> struct __is_inplace_index_imp : false_type {};
  50 template <size_t _Idx> struct __is_inplace_index_imp<in_place_index_t<_Idx>> : true_type {};
  51
  52 template <class _Tp>
  53 using __is_inplace_index = __is_inplace_index_imp<__remove_cvref_t<_Tp>>;
  54
  55 #endif // _LIBCPP_STD_VER >= 17
  56
  57 _LIBCPP_END_NAMESPACE_STD
  58
  59 #endif // _LIBCPP___UTILITY_IN_PLACE_H