69 lines
1.9 KiB
C++
69 lines
1.9 KiB
C++
/*
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* Copyright 2022 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <functional>
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#include <optional>
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#include <ftl/details/type_traits.h>
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namespace android::ftl {
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template <typename>
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struct Optional;
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namespace details {
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template <typename>
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struct is_optional : std::false_type {};
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template <typename T>
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struct is_optional<std::optional<T>> : std::true_type {};
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template <typename T>
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struct is_optional<Optional<T>> : std::true_type {};
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template <typename F, typename T>
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struct transform_result {
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using type = Optional<std::remove_cv_t<std::invoke_result_t<F, T>>>;
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};
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template <typename F, typename T>
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using transform_result_t = typename transform_result<F, T>::type;
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template <typename F, typename T>
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struct and_then_result {
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using type = remove_cvref_t<std::invoke_result_t<F, T>>;
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static_assert(is_optional<type>{}, "and_then function must return an optional");
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};
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template <typename F, typename T>
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using and_then_result_t = typename and_then_result<F, T>::type;
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template <typename F, typename T>
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struct or_else_result {
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using type = remove_cvref_t<std::invoke_result_t<F>>;
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static_assert(std::is_same_v<type, std::optional<T>> || std::is_same_v<type, Optional<T>>,
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"or_else function must return an optional T");
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};
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template <typename F, typename T>
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using or_else_result_t = typename or_else_result<F, T>::type;
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} // namespace details
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} // namespace android::ftl
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