libcxx/include/__compare/compare_partial_order_fallback.h

   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