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_WEAK_ORDER_FALLBACK 10 #define _LIBCPP___COMPARE_COMPARE_WEAK_ORDER_FALLBACK 11 12 #include <__compare/ordering.h> 13 #include <__compare/weak_order.h> 14 #include <__concepts/boolean_testable.h> 15 #include <__config> 16 #include <__type_traits/decay.h> 17 #include <__type_traits/is_same.h> 18 #include <__utility/forward.h> 19 #include <__utility/priority_tag.h> 20 21 #ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER 22 # pragma GCC system_header 23 #endif 24 25 _LIBCPP_BEGIN_NAMESPACE_STD 26 27 #if _LIBCPP_STD_VER >= 20 28 29 // [cmp.alg] 30 namespace __compare_weak_order_fallback { 31 struct __fn { 32 template <class _Tp, class _Up> 33 requires is_same_v<decay_t<_Tp>, decay_t<_Up>> 34 _LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_Tp&& __t, _Up&& __u, __priority_tag<1>) noexcept( 35 noexcept(std::weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) 36 -> decltype(std::weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))) { 37 return std::weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)); 38 } 39 40 template <class _Tp, class _Up> 41 requires is_same_v<decay_t<_Tp>, decay_t<_Up>> && requires(_Tp&& __t, _Up&& __u) { 42 { std::forward<_Tp>(__t) == std::forward<_Up>(__u) } -> __boolean_testable; 43 { std::forward<_Tp>(__t) < std::forward<_Up>(__u) } -> __boolean_testable; 44 } 45 _LIBCPP_HIDE_FROM_ABI static constexpr weak_ordering __go(_Tp&& __t, _Up&& __u, __priority_tag<0>) noexcept(noexcept( 46 std::forward<_Tp>(__t) == std::forward<_Up>(__u) ? weak_ordering::equivalent 47 : std::forward<_Tp>(__t) < std::forward<_Up>(__u) 48 ? weak_ordering::less 49 : weak_ordering::greater)) { 50 return std::forward<_Tp>(__t) == std::forward<_Up>(__u) ? weak_ordering::equivalent 51 : std::forward<_Tp>(__t) < std::forward<_Up>(__u) 52 ? weak_ordering::less 53 : weak_ordering::greater; 54 } 55 56 template <class _Tp, class _Up> 57 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const 58 noexcept(noexcept(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>()))) 59 -> decltype(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>())) { 60 return __go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>()); 61 } 62 }; 63 } // namespace __compare_weak_order_fallback 64 65 inline namespace __cpo { 66 inline constexpr auto compare_weak_order_fallback = __compare_weak_order_fallback::__fn{}; 67 } // namespace __cpo 68 69 #endif // _LIBCPP_STD_VER >= 20 70 71 _LIBCPP_END_NAMESPACE_STD 72 73 #endif // _LIBCPP___COMPARE_COMPARE_WEAK_ORDER_FALLBACK 74