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compare.hpp
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1
2// CPP, the Concepts PreProcessor library
3//
4// Copyright Eric Niebler 2018-present
5// Copyright (c) 2020-present, Google LLC.
6//
7// Use, modification and distribution is subject to the
8// Boost Software License, Version 1.0. (See accompanying
9// file LICENSE_1_0.txt or copy at
10// http://www.boost.org/LICENSE_1_0.txt)
11//
12// This source code is licensed under the MIT license found in the
13// LICENSE file in the root directory of this source tree.
14//
15// Project home: https://github.com/ericniebler/range-v3
16//
17#ifndef RANGES_V3_COMPARE_HPP
18#define RANGES_V3_COMPARE_HPP
19
20#if __cplusplus > 201703L && __has_include(<compare>) && \
21 defined(__cpp_concepts) && defined(__cpp_impl_three_way_comparison)
22
23#include <compare>
24#include <type_traits>
25
26namespace ranges
27{
28 template<typename... Ts>
29 struct common_comparison_category
30 {
31 using type = void;
32 };
33
34 template<typename... Ts>
35 requires ((std::is_same_v<Ts, std::partial_ordering> ||
36 std::is_same_v<Ts, std::weak_ordering> ||
37 std::is_same_v<Ts, std::strong_ordering>) && ...)
38 struct common_comparison_category<Ts...> : std::common_type<Ts...>
39 {};
40
41 template<typename... Ts>
42 using common_comparison_category_t = typename common_comparison_category<Ts...>::type;
43} // namespace ranges
44
45#endif // __cplusplus
46#endif // RANGES_V3_COMPARE_HPP