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_PREDICATE_H
10 #define _LIBCPP___CONCEPTS_PREDICATE_H
11 
12 #include <__concepts/boolean_testable.h>
13 #include <__concepts/invocable.h>
14 #include <__config>
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
24 
25 // [concept.predicate]
26 
27 template<class _Fn, class... _Args>
28 concept predicate =
29   regular_invocable<_Fn, _Args...> && __boolean_testable<invoke_result_t<_Fn, _Args...>>;
30 
31 #endif // _LIBCPP_STD_VER > 17
32 
33 _LIBCPP_END_NAMESPACE_STD
34 
35 #endif // _LIBCPP___CONCEPTS_PREDICATE_H
36