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_WEAK_ORDER_FALLBACK
10 #define _LIBCPP___COMPARE_COMPARE_WEAK_ORDER_FALLBACK
11 
12 #include <__compare/ordering.h>
13 #include <__compare/weak_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 > 17
27 
28 // [cmp.alg]
29 namespace __compare_weak_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::weak_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
36             -> decltype(      _VSTD::weak_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u)))
37             { return          _VSTD::weak_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) ? weak_ordering::equivalent :
44                               _VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u) ? weak_ordering::less :
45                               weak_ordering::greater))
46             -> decltype(      _VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u) ? weak_ordering::equivalent :
47                               _VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u) ? weak_ordering::less :
48                               weak_ordering::greater)
49         {
50             return            _VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u) ? weak_ordering::equivalent :
51                               _VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u) ? weak_ordering::less :
52                               weak_ordering::greater;
53         }
54 
55         template<class _Tp, class _Up>
56         _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
57             noexcept(noexcept(__go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<1>())))
58             -> decltype(      __go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<1>()))
59             { return          __go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<1>()); }
60     };
61 } // namespace __compare_weak_order_fallback
62 
63 inline namespace __cpo {
64     inline constexpr auto compare_weak_order_fallback = __compare_weak_order_fallback::__fn{};
65 } // namespace __cpo
66 
67 #endif // _LIBCPP_STD_VER > 17
68 
69 _LIBCPP_END_NAMESPACE_STD
70 
71 #endif // _LIBCPP___COMPARE_COMPARE_WEAK_ORDER_FALLBACK
72