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Telegram/ThirdParty/range-v3/include/concepts/compare.hpp

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+/// \file
+//  CPP, the Concepts PreProcessor library
+//
+//  Copyright Eric Niebler 2018-present
+//  Copyright (c) 2020-present, Google LLC.
+//
+//  Use, modification and distribution is subject to the
+//  Boost Software License, Version 1.0. (See accompanying
+//  file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt)
+//
+// This source code is licensed under the MIT license found in the
+// LICENSE file in the root directory of this source tree.
+//
+// Project home: https://github.com/ericniebler/range-v3
+//
+#ifndef CPP_COMPARE_HPP
+#define CPP_COMPARE_HPP
+
+#if __cplusplus > 201703L && __has_include(<compare>) && \
+    defined(__cpp_concepts) && defined(__cpp_impl_three_way_comparison)
+
+#include <compare>
+#include <concepts/concepts.hpp>
+#include <range/v3/compare.hpp>
+
+// clang-format off
+
+namespace concepts
+{
+    // Note: concepts in this file can use C++20 concepts, since operator<=> isn't available in
+    // compilers that don't support core concepts.
+    namespace detail
+    {
+        template<typename T, typename Cat>
+        concept compares_as = same_as<ranges::common_comparison_category_t<T, Cat>, Cat>;
+    } // namespace detail
+
+    inline namespace defs
+    {
+        template<typename T, typename Cat = std::partial_ordering>
+        concept three_way_comparable =
+            detail::weakly_equality_comparable_with_<T, T> &&
+            detail::partially_ordered_with_<T ,T> &&
+            requires(detail::as_cref_t<T>& a, detail::as_cref_t<T>& b) {
+                { a <=> b } -> detail::compares_as<Cat>;
+            };
+
+        template<typename T, typename U, typename Cat = std::partial_ordering>
+        concept three_way_comparable_with =
+            three_way_comparable<T, Cat> &&
+            three_way_comparable<U, Cat> &&
+            common_reference_with<detail::as_cref_t<T>&, detail::as_cref_t<U>&> &&
+            three_way_comparable<common_reference_t<detail::as_cref_t<T>&, detail::as_cref_t<U>&>> &&
+            detail::partially_ordered_with_<T, U> &&
+            requires(detail::as_cref_t<T>& t, detail::as_cref_t<U>& u) {
+                { t <=> u } -> detail::compares_as<Cat>;
+                { u <=> t } -> detail::compares_as<Cat>;
+            };
+    } // inline namespace defs
+} // namespace concepts
+
+// clang-format on
+
+#endif // __cplusplus
+#endif // CPP_COMPARE_HPP