libcxx/include/__cxx03/__concepts/boolean_testable.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_BOOLEAN_TESTABLE_H
  10 #define _LIBCPP___CONCEPTS_BOOLEAN_TESTABLE_H
  11
  12 #include <__cxx03/__concepts/convertible_to.h>
  13 #include <__cxx03/__config>
  14 #include <__cxx03/__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 // [concepts.booleantestable]
  25
  26 template <class _Tp>
  27 concept __boolean_testable_impl = convertible_to<_Tp, bool>;
  28
  29 template <class _Tp>
  30 concept __boolean_testable = __boolean_testable_impl<_Tp> && requires(_Tp&& __t) {
  31   { !std::forward<_Tp>(__t) } -> __boolean_testable_impl;
  32 };
  33
  34 #endif // _LIBCPP_STD_VER >= 20
  35
  36 _LIBCPP_END_NAMESPACE_STD
  37
  38 #endif // _LIBCPP___CONCEPTS_BOOLEAN_TESTABLE_H