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 <__type_traits/is_move_constructible.h>
  20 #include <__utility/forward.h>
  21
  22 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  23 #  pragma GCC system_header
  24 #endif
  25
  26 _LIBCPP_BEGIN_NAMESPACE_STD
  27
  28 #if _LIBCPP_STD_VER >= 17
  29
  30 struct __not_fn_op {
  31     template <class... _Args>
  32     _LIBCPP_HIDE_FROM_ABI
  33     _LIBCPP_CONSTEXPR_SINCE_CXX20 auto operator()(_Args&&... __args) const
  34         noexcept(noexcept(!_VSTD::invoke(_VSTD::forward<_Args>(__args)...)))
  35         -> decltype(      !_VSTD::invoke(_VSTD::forward<_Args>(__args)...))
  36         { return          !_VSTD::invoke(_VSTD::forward<_Args>(__args)...); }
  37 };
  38
  39 template <class _Fn>
  40 struct __not_fn_t : __perfect_forward<__not_fn_op, _Fn> {
  41     using __perfect_forward<__not_fn_op, _Fn>::__perfect_forward;
  42 };
  43
  44 template <class _Fn, class = enable_if_t<
  45     is_constructible_v<decay_t<_Fn>, _Fn> &&
  46     is_move_constructible_v<decay_t<_Fn>>
  47 >>
  48 _LIBCPP_HIDE_FROM_ABI
  49 _LIBCPP_CONSTEXPR_SINCE_CXX20 auto not_fn(_Fn&& __f) {
  50     return __not_fn_t<decay_t<_Fn>>(_VSTD::forward<_Fn>(__f));
  51 }
  52
  53 #endif // _LIBCPP_STD_VER >= 17
  54
  55 _LIBCPP_END_NAMESPACE_STD
  56
  57 #endif // _LIBCPP___FUNCTIONAL_NOT_FN_H