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]
32namespace __weak_order {
33void weak_order() = delete;
34
35struct __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
97inline namespace __cpo {
98inline 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