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_PARTIAL_ORDER
10 #define _LIBCPP___COMPARE_PARTIAL_ORDER
11 
12 #include <__compare/compare_three_way.h>
13 #include <__compare/ordering.h>
14 #include <__compare/weak_order.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 __partial_order {
31 struct __fn {
32   // NOLINTBEGIN(libcpp-robust-against-adl) partial_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<2>) noexcept(
36       noexcept(partial_ordering(partial_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))))
37       -> decltype(partial_ordering(partial_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
38     return partial_ordering(partial_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)));
39   }
40   // NOLINTEND(libcpp-robust-against-adl)
41 
42   template <class _Tp, class _Up>
43     requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
44   _LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_Tp&& __t, _Up&& __u, __priority_tag<1>) noexcept(
45       noexcept(partial_ordering(compare_three_way()(std::forward<_Tp>(__t), std::forward<_Up>(__u)))))
46       -> decltype(partial_ordering(compare_three_way()(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
47     return partial_ordering(compare_three_way()(std::forward<_Tp>(__t), std::forward<_Up>(__u)));
48   }
49 
50   template <class _Tp, class _Up>
51     requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
52   _LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_Tp&& __t, _Up&& __u, __priority_tag<0>) noexcept(
53       noexcept(partial_ordering(std::weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))))
54       -> decltype(partial_ordering(std::weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
55     return partial_ordering(std::weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)));
56   }
57 
58   template <class _Tp, class _Up>
59   _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
60       noexcept(noexcept(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<2>())))
61           -> decltype(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<2>())) {
62     return __go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<2>());
63   }
64 };
65 } // namespace __partial_order
66 
67 inline namespace __cpo {
68 inline constexpr auto partial_order = __partial_order::__fn{};
69 } // namespace __cpo
70 
71 #endif // _LIBCPP_STD_VER >= 20
72 
73 _LIBCPP_END_NAMESPACE_STD
74 
75 #endif // _LIBCPP___COMPARE_PARTIAL_ORDER
76