llvm-project/libcxx/include/__functional/not_fn.h

// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___FUNCTIONAL_NOT_FN_H
#define _LIBCPP___FUNCTIONAL_NOT_FN_H

#include <__config>
#include <__functional/invoke.h>
#include <__functional/perfect_forward.h>
#include <utility>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

#if _LIBCPP_STD_VER > 14

struct __not_fn_op {
    template <class... _Args>
    _LIBCPP_HIDE_FROM_ABI
    _LIBCPP_CONSTEXPR_AFTER_CXX17 auto operator()(_Args&&... __args) const
        noexcept(noexcept(!_VSTD::invoke(_VSTD::forward<_Args>(__args)...)))
        -> decltype(      !_VSTD::invoke(_VSTD::forward<_Args>(__args)...))
        { return          !_VSTD::invoke(_VSTD::forward<_Args>(__args)...); }
};

template <class _Fn>
struct __not_fn_t : __perfect_forward<__not_fn_op, _Fn> {
    using __perfect_forward<__not_fn_op, _Fn>::__perfect_forward;
};

template <class _Fn, class = enable_if_t<
    is_constructible_v<decay_t<_Fn>, _Fn> &&
    is_move_constructible_v<decay_t<_Fn>>
>>
_LIBCPP_HIDE_FROM_ABI
_LIBCPP_CONSTEXPR_AFTER_CXX17 auto not_fn(_Fn&& __f) {
    return __not_fn_t<decay_t<_Fn>>(_VSTD::forward<_Fn>(__f));
}

#endif // _LIBCPP_STD_VER > 14

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP___FUNCTIONAL_NOT_FN_H