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