73 lines
2.0 KiB
C++
73 lines
2.0 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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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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namespace folly {
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enum class ordering : int { lt = -1, eq = 0, gt = 1 };
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template <typename T>
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constexpr ordering to_ordering(T c) {
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return ordering(int(c < T(0)) * -1 + int(c > T(0)));
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}
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namespace detail {
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template <typename C, ordering o, bool ne>
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struct cmp_pred : private C {
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using C::C;
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template <typename A, typename B>
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constexpr bool operator()(A&& a, B&& b) const {
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return ne ^ (C::operator()(static_cast<A&&>(a), static_cast<B&&>(b)) == o);
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}
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};
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} // namespace detail
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template <typename C>
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struct compare_equal_to : detail::cmp_pred<C, ordering::eq, 0> {
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using detail::cmp_pred<C, ordering::eq, 0>::cmp_pred;
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};
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template <typename C>
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struct compare_not_equal_to : detail::cmp_pred<C, ordering::eq, 1> {
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using detail::cmp_pred<C, ordering::eq, 1>::cmp_pred;
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};
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template <typename C>
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struct compare_less : detail::cmp_pred<C, ordering::lt, 0> {
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using detail::cmp_pred<C, ordering::lt, 0>::cmp_pred;
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};
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template <typename C>
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struct compare_less_equal : detail::cmp_pred<C, ordering::gt, 1> {
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using detail::cmp_pred<C, ordering::gt, 1>::cmp_pred;
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};
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template <typename C>
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struct compare_greater : detail::cmp_pred<C, ordering::gt, 0> {
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using detail::cmp_pred<C, ordering::gt, 0>::cmp_pred;
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};
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template <typename C>
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struct compare_greater_equal : detail::cmp_pred<C, ordering::lt, 1> {
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using detail::cmp_pred<C, ordering::lt, 1>::cmp_pred;
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};
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} // namespace folly
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