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_PARTIAL_ORDER_FALLBACK
10 #define _LIBCPP___COMPARE_COMPARE_PARTIAL_ORDER_FALLBACK
11 
12 #include <__compare/ordering.h>
13 #include <__compare/partial_order.h>
14 #include <__config>
15 #include <__type_traits/decay.h>
16 #include <__type_traits/is_same.h>
17 #include <__utility/forward.h>
18 #include <__utility/priority_tag.h>
19 
20 #ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
21 #  pragma GCC system_header
22 #endif
23 
24 _LIBCPP_BEGIN_NAMESPACE_STD
25 
26 #if _LIBCPP_STD_VER >= 20
27 
28 // [cmp.alg]
29 namespace __compare_partial_order_fallback {
30     struct __fn {
31         template<class _Tp, class _Up>
32             requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
33         _LIBCPP_HIDE_FROM_ABI static constexpr auto
34         __go(_Tp&& __t, _Up&& __u, __priority_tag<1>)
35             noexcept(noexcept(_VSTD::partial_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
36             -> decltype(      _VSTD::partial_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u)))
37             { return          _VSTD::partial_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u)); }
38 
39         template<class _Tp, class _Up>
40             requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
41         _LIBCPP_HIDE_FROM_ABI static constexpr auto
42         __go(_Tp&& __t, _Up&& __u, __priority_tag<0>)
43             noexcept(noexcept(_VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u) ? partial_ordering::equivalent :
44                               _VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u) ? partial_ordering::less :
45                               _VSTD::forward<_Up>(__u) < _VSTD::forward<_Tp>(__t) ? partial_ordering::greater :
46                               partial_ordering::unordered))
47             -> decltype(      _VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u) ? partial_ordering::equivalent :
48                               _VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u) ? partial_ordering::less :
49                               _VSTD::forward<_Up>(__u) < _VSTD::forward<_Tp>(__t) ? partial_ordering::greater :
50                               partial_ordering::unordered)
51         {
52             return            _VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u) ? partial_ordering::equivalent :
53                               _VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u) ? partial_ordering::less :
54                               _VSTD::forward<_Up>(__u) < _VSTD::forward<_Tp>(__t) ? partial_ordering::greater :
55                               partial_ordering::unordered;
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(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<1>())))
61             -> decltype(      __go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<1>()))
62             { return          __go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<1>()); }
63     };
64 } // namespace __compare_partial_order_fallback
65 
66 inline namespace __cpo {
67     inline constexpr auto compare_partial_order_fallback = __compare_partial_order_fallback::__fn{};
68 } // namespace __cpo
69 
70 #endif // _LIBCPP_STD_VER >= 20
71 
72 _LIBCPP_END_NAMESPACE_STD
73 
74 #endif // _LIBCPP___COMPARE_COMPARE_PARTIAL_ORDER_FALLBACK
75