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_SYNTH_THREE_WAY_H
10#define _LIBCPP___COMPARE_SYNTH_THREE_WAY_H
11
12#include <__compare/ordering.h>
13#include <__compare/three_way_comparable.h>
14#include <__concepts/boolean_testable.h>
15#include <__config>
16#include <__utility/declval.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// [expos.only.func]
27
28_LIBCPP_HIDE_FROM_ABI inline constexpr auto __synth_three_way = []<class _Tp, class _Up>(const _Tp& __t, const _Up& __u)
29 requires requires {
30 { __t < __u } -> __boolean_testable;
31 { __u < __t } -> __boolean_testable;
32 }
33{
34 if constexpr (three_way_comparable_with<_Tp, _Up>) {
35 return __t <=> __u;
36 } else {
37 if (__t < __u)
38 return weak_ordering::less;
39 if (__u < __t)
40 return weak_ordering::greater;
41 return weak_ordering::equivalent;
42 }
43};
44
45template <class _Tp, class _Up = _Tp>
46using __synth_three_way_result _LIBCPP_NODEBUG =
47 decltype(std::__synth_three_way(std::declval<_Tp&>(), std::declval<_Up&>()));
48
49#endif // _LIBCPP_STD_VER >= 20
50
51_LIBCPP_END_NAMESPACE_STD
52
53#endif // _LIBCPP___COMPARE_SYNTH_THREE_WAY_H
54