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