1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef _LIBCPP___COMPARE_THREE_WAY_COMPARABLE_H
10#define _LIBCPP___COMPARE_THREE_WAY_COMPARABLE_H
11
12#include <__compare/common_comparison_category.h>
13#include <__compare/ordering.h>
14#include <__concepts/common_reference_with.h>
15#include <__concepts/equality_comparable.h>
16#include <__concepts/same_as.h>
17#include <__concepts/totally_ordered.h>
18#include <__config>
19#include <__type_traits/common_reference.h>
20#include <__type_traits/make_const_lvalue_ref.h>
21
22#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
23# pragma GCC system_header
24#endif
25
26_LIBCPP_BEGIN_NAMESPACE_STD
27
28#if _LIBCPP_STD_VER >= 20
29
30template <class _Tp, class _Cat>
31concept __compares_as = same_as<common_comparison_category_t<_Tp, _Cat>, _Cat>;
32
33template <class _Tp, class _Cat = partial_ordering>
34concept three_way_comparable =
35 __weakly_equality_comparable_with<_Tp, _Tp> && __partially_ordered_with<_Tp, _Tp> &&
36 requires(__make_const_lvalue_ref<_Tp> __a, __make_const_lvalue_ref<_Tp> __b) {
37 { __a <=> __b } -> __compares_as<_Cat>;
38 };
39
40template <class _Tp, class _Up, class _Cat = partial_ordering>
41concept three_way_comparable_with =
42 three_way_comparable<_Tp, _Cat> && three_way_comparable<_Up, _Cat> &&
43 common_reference_with<__make_const_lvalue_ref<_Tp>, __make_const_lvalue_ref<_Up>> &&
44 three_way_comparable<common_reference_t<__make_const_lvalue_ref<_Tp>, __make_const_lvalue_ref<_Up>>, _Cat> &&
45 __weakly_equality_comparable_with<_Tp, _Up> && __partially_ordered_with<_Tp, _Up> &&
46 requires(__make_const_lvalue_ref<_Tp> __t, __make_const_lvalue_ref<_Up> __u) {
47 { __t <=> __u } -> __compares_as<_Cat>;
48 { __u <=> __t } -> __compares_as<_Cat>;
49 };
50
51#endif // _LIBCPP_STD_VER >= 20
52
53_LIBCPP_END_NAMESPACE_STD
54
55#endif // _LIBCPP___COMPARE_THREE_WAY_COMPARABLE_H
56