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 #include <type_traits>
  16
  17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  18 #pragma GCC system_header
  19 #endif
  20
  21 _LIBCPP_BEGIN_NAMESPACE_STD
  22
  23 #if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
  24
  25 // [concept.invocable]
  26
  27 template<class _Fn, class... _Args>
  28 concept invocable = requires(_Fn&& __fn, _Args&&... __args) {
  29   _VSTD::invoke(_VSTD::forward<_Fn>(__fn), _VSTD::forward<_Args>(__args)...); // not required to be equality preserving
  30 };
  31
  32 // [concept.regular.invocable]
  33
  34 template<class _Fn, class... _Args>
  35 concept regular_invocable = invocable<_Fn, _Args...>;
  36
  37 #endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
  38
  39 _LIBCPP_END_NAMESPACE_STD
  40
  41 #endif // _LIBCPP___CONCEPTS_INVOCABLE_H