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