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 // TODO MODULES restore the lamba to match the Standard. 29 // See https://github.com/llvm/llvm-project/issues/57222 30 //_LIBCPP_HIDE_FROM_ABI inline constexpr auto __synth_three_way = 31 // []<class _Tp, class _Up>(const _Tp& __t, const _Up& __u) 32 template <class _Tp, class _Up> 33 _LIBCPP_HIDE_FROM_ABI constexpr auto __synth_three_way(const _Tp& __t, const _Up& __u) 34 requires requires { 35 { __t < __u } -> __boolean_testable; 36 { __u < __t } -> __boolean_testable; 37 } 38 { 39 if constexpr (three_way_comparable_with<_Tp, _Up>) { 40 return __t <=> __u; 41 } else { 42 if (__t < __u) 43 return weak_ordering::less; 44 if (__u < __t) 45 return weak_ordering::greater; 46 return weak_ordering::equivalent; 47 } 48 } 49 50 template <class _Tp, class _Up = _Tp> 51 using __synth_three_way_result = decltype(std::__synth_three_way(std::declval<_Tp&>(), std::declval<_Up&>())); 52 53 #endif // _LIBCPP_STD_VER >= 20 54 55 _LIBCPP_END_NAMESPACE_STD 56 57 #endif // _LIBCPP___COMPARE_SYNTH_THREE_WAY_H 58