libcxx/include/__functional/not_fn.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___FUNCTIONAL_NOT_FN_H
  11 #define _LIBCPP___FUNCTIONAL_NOT_FN_H
  12
  13 #include <__config>
  14 #include <__functional/invoke.h>
  15 #include <__functional/perfect_forward.h>
  16 #include <__type_traits/decay.h>
  17 #include <__type_traits/enable_if.h>
  18 #include <__type_traits/is_constructible.h>
  19 #include <__utility/forward.h>
  20
  21 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  22 #  pragma GCC system_header
  23 #endif
  24
  25 _LIBCPP_BEGIN_NAMESPACE_STD
  26
  27 #if _LIBCPP_STD_VER >= 17
  28
  29 struct __not_fn_op {
  30   template <class... _Args>
  31   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 auto operator()(_Args&&... __args) const
  32       noexcept(noexcept(!std::invoke(std::forward<_Args>(__args)...)))
  33           -> decltype(!std::invoke(std::forward<_Args>(__args)...)) {
  34     return !std::invoke(std::forward<_Args>(__args)...);
  35   }
  36 };
  37
  38 template <class _Fn>
  39 struct __not_fn_t : __perfect_forward<__not_fn_op, _Fn> {
  40   using __perfect_forward<__not_fn_op, _Fn>::__perfect_forward;
  41 };
  42
  43 template <class _Fn,
  44           class = enable_if_t< is_constructible_v<decay_t<_Fn>, _Fn> && is_move_constructible_v<decay_t<_Fn>> >>
  45 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 auto not_fn(_Fn&& __f) {
  46   return __not_fn_t<decay_t<_Fn>>(std::forward<_Fn>(__f));
  47 }
  48
  49 #endif // _LIBCPP_STD_VER >= 17
  50
  51 _LIBCPP_END_NAMESPACE_STD
  52
  53 #endif // _LIBCPP___FUNCTIONAL_NOT_FN_H