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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 > 17 25 26 // [expos.only.func] 27 28 _LIBCPP_HIDE_FROM_ABI inline constexpr auto __synth_three_way = 29 []<class _Tp, class _Up>(const _Tp& __t, const _Up& __u) 30 requires requires { 31 { __t < __u } -> __boolean_testable; 32 { __u < __t } -> __boolean_testable; 33 } 34 { 35 if constexpr (three_way_comparable_with<_Tp, _Up>) { 36 return __t <=> __u; 37 } else { 38 if (__t < __u) return weak_ordering::less; 39 if (__u < __t) return weak_ordering::greater; 40 return weak_ordering::equivalent; 41 } 42 }; 43 44 template <class _Tp, class _Up = _Tp> 45 using __synth_three_way_result = decltype(std::__synth_three_way(declval<_Tp&>(), declval<_Up&>())); 46 47 #endif // _LIBCPP_STD_VER > 17 48 49 _LIBCPP_END_NAMESPACE_STD 50 51 #endif // _LIBCPP___COMPARE_SYNTH_THREE_WAY_H