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___CONCEPTS_EQUALITY_COMPARABLE_H
10#define _LIBCPP___CONCEPTS_EQUALITY_COMPARABLE_H
11
12#include <__concepts/boolean_testable.h>
13#include <__concepts/common_reference_with.h>
14#include <__concepts/comparison_common_type.h>
15#include <__config>
16#include <__type_traits/common_reference.h>
17#include <__type_traits/make_const_lvalue_ref.h>
18
19#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20# pragma GCC system_header
21#endif
22
23_LIBCPP_BEGIN_NAMESPACE_STD
24
25#if _LIBCPP_STD_VER >= 20
26
27// [concept.equalitycomparable]
28
29template <class _Tp, class _Up>
30concept __weakly_equality_comparable_with =
31 requires(__make_const_lvalue_ref<_Tp> __t, __make_const_lvalue_ref<_Up> __u) {
32 { __t == __u } -> __boolean_testable;
33 { __t != __u } -> __boolean_testable;
34 { __u == __t } -> __boolean_testable;
35 { __u != __t } -> __boolean_testable;
36 };
37
38template <class _Tp>
39concept equality_comparable = __weakly_equality_comparable_with<_Tp, _Tp>;
40
41// clang-format off
42template <class _Tp, class _Up>
43concept equality_comparable_with =
44 equality_comparable<_Tp> && equality_comparable<_Up> &&
45 __comparison_common_type_with<_Tp, _Up> &&
46 equality_comparable<
47 common_reference_t<
48 __make_const_lvalue_ref<_Tp>,
49 __make_const_lvalue_ref<_Up>>> &&
50 __weakly_equality_comparable_with<_Tp, _Up>;
51// clang-format on
52
53#endif // _LIBCPP_STD_VER >= 20
54
55_LIBCPP_END_NAMESPACE_STD
56
57#endif // _LIBCPP___CONCEPTS_EQUALITY_COMPARABLE_H
58