v1/__compare/compare_three_way_result.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___COMPARE_COMPARE_THREE_WAY_RESULT_H
0010 #define _LIBCPP___COMPARE_COMPARE_THREE_WAY_RESULT_H
0011
0012 #include <__config>
0013 #include <__type_traits/make_const_lvalue_ref.h>
0014 #include <__utility/declval.h>
0015
0016 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0017 #  pragma GCC system_header
0018 #endif
0019
0020 _LIBCPP_BEGIN_NAMESPACE_STD
0021
0022 #if _LIBCPP_STD_VER >= 20
0023
0024 template <class, class, class>
0025 struct _LIBCPP_HIDE_FROM_ABI __compare_three_way_result {};
0026
0027 template <class _Tp, class _Up>
0028 struct _LIBCPP_HIDE_FROM_ABI __compare_three_way_result<
0029     _Tp,
0030     _Up,
0031     decltype(std::declval<__make_const_lvalue_ref<_Tp>>() <=> std::declval<__make_const_lvalue_ref<_Up>>(), void())> {
0032   using type = decltype(std::declval<__make_const_lvalue_ref<_Tp>>() <=> std::declval<__make_const_lvalue_ref<_Up>>());
0033 };
0034
0035 template <class _Tp, class _Up = _Tp>
0036 struct _LIBCPP_TEMPLATE_VIS _LIBCPP_NO_SPECIALIZATIONS compare_three_way_result
0037     : __compare_three_way_result<_Tp, _Up, void> {};
0038
0039 template <class _Tp, class _Up = _Tp>
0040 using compare_three_way_result_t = typename compare_three_way_result<_Tp, _Up>::type;
0041
0042 #endif // _LIBCPP_STD_VER >= 20
0043
0044 _LIBCPP_END_NAMESPACE_STD
0045
0046 #endif // _LIBCPP___COMPARE_COMPARE_THREE_WAY_RESULT_H