libcxx/include/__concepts/invocable.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___CONCEPTS_INVOCABLE_H
  10 #define _LIBCPP___CONCEPTS_INVOCABLE_H
  11
  12 #include <__config>
  13 #include <__functional/invoke.h>
  14 #include <__utility/forward.h>
  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 >= 20
  23
  24 // [concept.invocable]
  25
  26 template <class _Fn, class... _Args>
  27 concept invocable = requires(_Fn&& __fn, _Args&&... __args) {
  28   std::invoke(std::forward<_Fn>(__fn), std::forward<_Args>(__args)...); // not required to be equality preserving
  29 };
  30
  31 // [concept.regular.invocable]
  32
  33 template <class _Fn, class... _Args>
  34 concept regular_invocable = invocable<_Fn, _Args...>;
  35
  36 #endif // _LIBCPP_STD_VER >= 20
  37
  38 _LIBCPP_END_NAMESPACE_STD
  39
  40 #endif // _LIBCPP___CONCEPTS_INVOCABLE_H