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9fbe4850c9
collection-concepts includes a Comparable concept for a trichotomic comparator function, used in intrusive btree and double_decker. Prepare for std::strong_ordering by also allowing std::strong_ordering as a return type. Once we've cleaned the code base, we can tighten it to only allow std::strong_ordering.
53 lines
1.9 KiB
C++
53 lines
1.9 KiB
C++
/*
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* Copyright (C) 2020 ScyllaDB
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*/
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/*
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* This file is part of Scylla.
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*
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* Scylla is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Scylla is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <type_traits>
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#include <seastar/util/concepts.hh>
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#include <compare>
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template <typename Func, typename T>
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concept Disposer = requires (Func f, T* val) {
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{ f(val) } noexcept -> std::same_as<void>;
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};
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template <typename Key1, typename Key2, typename Less>
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concept LessComparable = requires (const Key1& a, const Key2& b, Less less) {
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{ less(a, b) } -> std::same_as<bool>;
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{ less(b, a) } -> std::same_as<bool>;
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};
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template <typename Key1, typename Key2, typename Less>
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concept LessNothrowComparable = LessComparable<Key1, Key2, Less> && std::is_nothrow_invocable_v<Less, Key1, Key2>;
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// Temporary scaffolding for supporting trichotomic compares
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// that return either int or std::strong_ordering
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template <typename T>
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concept int_or_strong_ordering = std::same_as<T, int> || std::same_as<T, std::strong_ordering>;
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template <typename T1, typename T2, typename Compare>
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concept Comparable = requires (const T1& a, const T2& b, Compare cmp) {
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// The Comparable is trichotomic comparator that should return
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// negative value when a < b
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// zero when a == b
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// positive value when a > b
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{ cmp(a, b) } -> int_or_strong_ordering;
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}; |