57 lines
1.4 KiB
C++
57 lines
1.4 KiB
C++
// Copyright 2020 The Chromium Authors
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_FUNCTIONAL_NOT_FN_H_
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#define BASE_FUNCTIONAL_NOT_FN_H_
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#include <type_traits>
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#include <utility>
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#include "base/functional/invoke.h"
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namespace base {
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namespace internal {
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template <typename F>
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struct NotFnImpl {
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F f;
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template <typename... Args>
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constexpr decltype(auto) operator()(Args&&... args) & noexcept {
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return !base::invoke(f, std::forward<Args>(args)...);
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}
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template <typename... Args>
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constexpr decltype(auto) operator()(Args&&... args) const& noexcept {
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return !base::invoke(f, std::forward<Args>(args)...);
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}
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template <typename... Args>
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constexpr decltype(auto) operator()(Args&&... args) && noexcept {
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return !base::invoke(std::move(f), std::forward<Args>(args)...);
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}
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template <typename... Args>
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constexpr decltype(auto) operator()(Args&&... args) const&& noexcept {
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return !base::invoke(std::move(f), std::forward<Args>(args)...);
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}
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};
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} // namespace internal
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// Implementation of C++17's std::not_fn.
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//
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// Reference:
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// - https://en.cppreference.com/w/cpp/utility/functional/not_fn
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// - https://wg21.link/func.not.fn
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template <typename F>
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constexpr internal::NotFnImpl<std::decay_t<F>> not_fn(F&& f) {
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return {std::forward<F>(f)};
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}
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} // namespace base
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#endif // BASE_FUNCTIONAL_NOT_FN_H_
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