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_WEAK_ORDER 10 #define _LIBCPP___COMPARE_WEAK_ORDER 11 12 #include <__compare/compare_three_way.h> 13 #include <__compare/ordering.h> 14 #include <__compare/strong_order.h> 15 #include <__config> 16 #include <__math/traits.h> 17 #include <__type_traits/decay.h> 18 #include <__type_traits/is_floating_point.h> 19 #include <__type_traits/is_same.h> 20 #include <__utility/forward.h> 21 #include <__utility/priority_tag.h> 22 23 #ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER 24 # pragma GCC system_header 25 #endif 26 27 _LIBCPP_BEGIN_NAMESPACE_STD 28 29 #if _LIBCPP_STD_VER >= 20 30 31 // [cmp.alg] 32 namespace __weak_order { 33 void weak_order() = delete; 34 35 struct __fn { 36 // NOLINTBEGIN(libcpp-robust-against-adl) weak_order should use ADL, but only here 37 template <class _Tp, class _Up> 38 requires is_same_v<decay_t<_Tp>, decay_t<_Up>> 39 _LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_Tp&& __t, _Up&& __u, __priority_tag<3>) noexcept( 40 noexcept(weak_ordering(weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))))) 41 -> decltype(weak_ordering(weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) { 42 return weak_ordering(weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))); 43 } 44 // NOLINTEND(libcpp-robust-against-adl) 45 46 template <class _Tp, class _Up, class _Dp = decay_t<_Tp>> 47 requires is_same_v<_Dp, decay_t<_Up>> && is_floating_point_v<_Dp> 48 _LIBCPP_HIDE_FROM_ABI static constexpr weak_ordering __go(_Tp&& __t, _Up&& __u, __priority_tag<2>) noexcept { 49 partial_ordering __po = (__t <=> __u); 50 if (__po == partial_ordering::less) { 51 return weak_ordering::less; 52 } else if (__po == partial_ordering::equivalent) { 53 return weak_ordering::equivalent; 54 } else if (__po == partial_ordering::greater) { 55 return weak_ordering::greater; 56 } else { 57 // Otherwise, at least one of them is a NaN. 58 bool __t_is_nan = __math::isnan(__t); 59 bool __u_is_nan = __math::isnan(__u); 60 bool __t_is_negative = __math::signbit(__t); 61 bool __u_is_negative = __math::signbit(__u); 62 if (__t_is_nan && __u_is_nan) { 63 return (__u_is_negative <=> __t_is_negative); 64 } else if (__t_is_nan) { 65 return __t_is_negative ? weak_ordering::less : weak_ordering::greater; 66 } else { 67 return __u_is_negative ? weak_ordering::greater : weak_ordering::less; 68 } 69 } 70 } 71 72 template <class _Tp, class _Up> 73 requires is_same_v<decay_t<_Tp>, decay_t<_Up>> 74 _LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_Tp&& __t, _Up&& __u, __priority_tag<1>) noexcept( 75 noexcept(weak_ordering(compare_three_way()(std::forward<_Tp>(__t), std::forward<_Up>(__u))))) 76 -> decltype(weak_ordering(compare_three_way()(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) { 77 return weak_ordering(compare_three_way()(std::forward<_Tp>(__t), std::forward<_Up>(__u))); 78 } 79 80 template <class _Tp, class _Up> 81 requires is_same_v<decay_t<_Tp>, decay_t<_Up>> 82 _LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_Tp&& __t, _Up&& __u, __priority_tag<0>) noexcept( 83 noexcept(weak_ordering(std::strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))))) 84 -> decltype(weak_ordering(std::strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) { 85 return weak_ordering(std::strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))); 86 } 87 88 template <class _Tp, class _Up> 89 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const 90 noexcept(noexcept(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<3>()))) 91 -> decltype(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<3>())) { 92 return __go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<3>()); 93 } 94 }; 95 } // namespace __weak_order 96 97 inline namespace __cpo { 98 inline constexpr auto weak_order = __weak_order::__fn{}; 99 } // namespace __cpo 100 101 #endif // _LIBCPP_STD_VER >= 20 102 103 _LIBCPP_END_NAMESPACE_STD 104 105 #endif // _LIBCPP___COMPARE_WEAK_ORDER 106