libcxx/include/__compare/compare_strong_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_STRONG_ORDER_FALLBACK
  10 #define _LIBCPP___COMPARE_COMPARE_STRONG_ORDER_FALLBACK
  11
  12 #include <__compare/ordering.h>
  13 #include <__compare/strong_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_strong_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::strong_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
  36             -> decltype(      _VSTD::strong_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u)))
  37             { return          _VSTD::strong_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) ? strong_ordering::equal :
  44                               _VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u) ? strong_ordering::less :
  45                               strong_ordering::greater))
  46             -> decltype(      _VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u) ? strong_ordering::equal :
  47                               _VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u) ? strong_ordering::less :
  48                               strong_ordering::greater)
  49         {
  50             return            _VSTD::forward<_Tp>(__t) == _VSTD::forward<_Up>(__u) ? strong_ordering::equal :
  51                               _VSTD::forward<_Tp>(__t) < _VSTD::forward<_Up>(__u) ? strong_ordering::less :
  52                               strong_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_strong_order_fallback
  62
  63 inline namespace __cpo {
  64     inline constexpr auto compare_strong_order_fallback = __compare_strong_order_fallback::__fn{};
  65 } // namespace __cpo
  66
  67 #endif // _LIBCPP_STD_VER >= 20
  68
  69 _LIBCPP_END_NAMESPACE_STD
  70
  71 #endif // _LIBCPP___COMPARE_COMPARE_STRONG_ORDER_FALLBACK