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_COMPARE_THREE_WAY_RESULT_H
10#define _LIBCPP___COMPARE_COMPARE_THREE_WAY_RESULT_H
11
12#include <__config>
13#include <__type_traits/make_const_lvalue_ref.h>
14#include <__utility/declval.h>
15
16#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
17#  pragma GCC system_header
18#endif
19
20_LIBCPP_BEGIN_NAMESPACE_STD
21
22#if _LIBCPP_STD_VER > 17
23
24template<class, class, class>
25struct _LIBCPP_HIDE_FROM_ABI __compare_three_way_result { };
26
27template<class _Tp, class _Up>
28struct _LIBCPP_HIDE_FROM_ABI __compare_three_way_result<_Tp, _Up, decltype(
29  std::declval<__make_const_lvalue_ref<_Tp>>() <=> std::declval<__make_const_lvalue_ref<_Up>>(), void()
30)> {
31    using type = decltype(std::declval<__make_const_lvalue_ref<_Tp>>() <=> std::declval<__make_const_lvalue_ref<_Up>>());
32};
33
34template<class _Tp, class _Up = _Tp>
35struct _LIBCPP_TEMPLATE_VIS compare_three_way_result : __compare_three_way_result<_Tp, _Up, void> { };
36
37template<class _Tp, class _Up = _Tp>
38using compare_three_way_result_t = typename compare_three_way_result<_Tp, _Up>::type;
39
40#endif // _LIBCPP_STD_VER > 17
41
42_LIBCPP_END_NAMESPACE_STD
43
44#endif // _LIBCPP___COMPARE_COMPARE_THREE_WAY_RESULT_H
45