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 <utility>
  17
  18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  19 #pragma GCC system_header
  20 #endif
  21
  22 _LIBCPP_BEGIN_NAMESPACE_STD
  23
  24 #if _LIBCPP_STD_VER > 14
  25
  26 struct __not_fn_op {
  27     template <class... _Args>
  28     _LIBCPP_HIDE_FROM_ABI
  29     _LIBCPP_CONSTEXPR_AFTER_CXX17 auto operator()(_Args&&... __args) const
  30         noexcept(noexcept(!_VSTD::invoke(_VSTD::forward<_Args>(__args)...)))
  31         -> decltype(      !_VSTD::invoke(_VSTD::forward<_Args>(__args)...))
  32         { return          !_VSTD::invoke(_VSTD::forward<_Args>(__args)...); }
  33 };
  34
  35 template <class _Fn>
  36 struct __not_fn_t : __perfect_forward<__not_fn_op, _Fn> {
  37     using __perfect_forward<__not_fn_op, _Fn>::__perfect_forward;
  38 };
  39
  40 template <class _Fn, class = enable_if_t<
  41     is_constructible_v<decay_t<_Fn>, _Fn> &&
  42     is_move_constructible_v<decay_t<_Fn>>
  43 >>
  44 _LIBCPP_HIDE_FROM_ABI
  45 _LIBCPP_CONSTEXPR_AFTER_CXX17 auto not_fn(_Fn&& __f) {
  46     return __not_fn_t<decay_t<_Fn>>(_VSTD::forward<_Fn>(__f));
  47 }
  48
  49 #endif // _LIBCPP_STD_VER > 14
  50
  51 _LIBCPP_END_NAMESPACE_STD
  52
  53 #endif // _LIBCPP___FUNCTIONAL_NOT_FN_H