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