__cxx03/__compare/compare_strong_order_fallback.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___CXX03___COMPARE_COMPARE_STRONG_ORDER_FALLBACK
0010 #define _LIBCPP___CXX03___COMPARE_COMPARE_STRONG_ORDER_FALLBACK
0011
0012 #include <__cxx03/__compare/ordering.h>
0013 #include <__cxx03/__compare/strong_order.h>
0014 #include <__cxx03/__config>
0015 #include <__cxx03/__type_traits/decay.h>
0016 #include <__cxx03/__type_traits/is_same.h>
0017 #include <__cxx03/__utility/forward.h>
0018 #include <__cxx03/__utility/priority_tag.h>
0019
0020 #ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
0021 #  pragma GCC system_header
0022 #endif
0023
0024 _LIBCPP_BEGIN_NAMESPACE_STD
0025
0026 #if _LIBCPP_STD_VER >= 20
0027
0028 // [cmp.alg]
0029 namespace __compare_strong_order_fallback {
0030 struct __fn {
0031   template <class _Tp, class _Up>
0032     requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
0033   _LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_Tp&& __t, _Up&& __u, __priority_tag<1>) noexcept(
0034       noexcept(std::strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))))
0035       -> decltype(std::strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))) {
0036     return std::strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u));
0037   }
0038
0039   template <class _Tp, class _Up>
0040     requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
0041   _LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_Tp&& __t, _Up&& __u, __priority_tag<0>) noexcept(noexcept(
0042       std::forward<_Tp>(__t) == std::forward<_Up>(__u) ? strong_ordering::equal
0043       : std::forward<_Tp>(__t) < std::forward<_Up>(__u)
0044           ? strong_ordering::less
0045           : strong_ordering::greater))
0046       -> decltype(std::forward<_Tp>(__t) == std::forward<_Up>(__u) ? strong_ordering::equal
0047                   : std::forward<_Tp>(__t) < std::forward<_Up>(__u)
0048                       ? strong_ordering::less
0049                       : strong_ordering::greater) {
0050     return std::forward<_Tp>(__t) == std::forward<_Up>(__u) ? strong_ordering::equal
0051          : std::forward<_Tp>(__t) < std::forward<_Up>(__u)
0052              ? strong_ordering::less
0053              : strong_ordering::greater;
0054   }
0055
0056   template <class _Tp, class _Up>
0057   _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
0058       noexcept(noexcept(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>())))
0059           -> decltype(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>())) {
0060     return __go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>());
0061   }
0062 };
0063 } // namespace __compare_strong_order_fallback
0064
0065 inline namespace __cpo {
0066 inline constexpr auto compare_strong_order_fallback = __compare_strong_order_fallback::__fn{};
0067 } // namespace __cpo
0068
0069 #endif // _LIBCPP_STD_VER >= 20
0070
0071 _LIBCPP_END_NAMESPACE_STD
0072
0073 #endif // _LIBCPP___CXX03___COMPARE_COMPARE_STRONG_ORDER_FALLBACK