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 > 17
29 
30 template<class _Tp, class _Cat>
31 concept __compares_as =
32   same_as<common_comparison_category_t<_Tp, _Cat>, _Cat>;
33 
34 template<class _Tp, class _Cat = partial_ordering>
35 concept three_way_comparable =
36   __weakly_equality_comparable_with<_Tp, _Tp> &&
37   __partially_ordered_with<_Tp, _Tp> &&
38   requires(__make_const_lvalue_ref<_Tp> __a, __make_const_lvalue_ref<_Tp> __b) {
39     { __a <=> __b } -> __compares_as<_Cat>;
40   };
41 
42 template<class _Tp, class _Up, class _Cat = partial_ordering>
43 concept three_way_comparable_with =
44   three_way_comparable<_Tp, _Cat> &&
45   three_way_comparable<_Up, _Cat> &&
46   common_reference_with<__make_const_lvalue_ref<_Tp>, __make_const_lvalue_ref<_Up>> &&
47   three_way_comparable<common_reference_t<__make_const_lvalue_ref<_Tp>, __make_const_lvalue_ref<_Up>>, _Cat> &&
48   __weakly_equality_comparable_with<_Tp, _Up> &&
49   __partially_ordered_with<_Tp, _Up> &&
50   requires(__make_const_lvalue_ref<_Tp> __t, __make_const_lvalue_ref<_Up> __u) {
51     { __t <=> __u } -> __compares_as<_Cat>;
52     { __u <=> __t } -> __compares_as<_Cat>;
53   };
54 
55 #endif // _LIBCPP_STD_VER > 17
56 
57 _LIBCPP_END_NAMESPACE_STD
58 
59 #endif // _LIBCPP___COMPARE_THREE_WAY_COMPARABLE_H
60