libcxx/include/__compare/partial_order.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_PARTIAL_ORDER
  10 #define _LIBCPP___COMPARE_PARTIAL_ORDER
  11
  12 #include <__compare/compare_three_way.h>
  13 #include <__compare/ordering.h>
  14 #include <__compare/weak_order.h>
  15 #include <__config>
  16 #include <__type_traits/decay.h>
  17 #include <__type_traits/is_same.h>
  18 #include <__utility/forward.h>
  19 #include <__utility/priority_tag.h>
  20
  21 #ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
  22 #  pragma GCC system_header
  23 #endif
  24
  25 _LIBCPP_BEGIN_NAMESPACE_STD
  26
  27 #if _LIBCPP_STD_VER >= 20
  28
  29 // [cmp.alg]
  30 namespace __partial_order {
  31 void partial_order() = delete;
  32
  33 struct __fn {
  34   // NOLINTBEGIN(libcpp-robust-against-adl) partial_order should use ADL, but only here
  35   template <class _Tp, class _Up>
  36     requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
  37   _LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_Tp&& __t, _Up&& __u, __priority_tag<2>) noexcept(
  38       noexcept(partial_ordering(partial_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))))
  39       -> decltype(partial_ordering(partial_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
  40     return partial_ordering(partial_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)));
  41   }
  42   // NOLINTEND(libcpp-robust-against-adl)
  43
  44   template <class _Tp, class _Up>
  45     requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
  46   _LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_Tp&& __t, _Up&& __u, __priority_tag<1>) noexcept(
  47       noexcept(partial_ordering(compare_three_way()(std::forward<_Tp>(__t), std::forward<_Up>(__u)))))
  48       -> decltype(partial_ordering(compare_three_way()(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
  49     return partial_ordering(compare_three_way()(std::forward<_Tp>(__t), std::forward<_Up>(__u)));
  50   }
  51
  52   template <class _Tp, class _Up>
  53     requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
  54   _LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_Tp&& __t, _Up&& __u, __priority_tag<0>) noexcept(
  55       noexcept(partial_ordering(std::weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))))
  56       -> decltype(partial_ordering(std::weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
  57     return partial_ordering(std::weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)));
  58   }
  59
  60   template <class _Tp, class _Up>
  61   _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
  62       noexcept(noexcept(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<2>())))
  63           -> decltype(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<2>())) {
  64     return __go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<2>());
  65   }
  66 };
  67 } // namespace __partial_order
  68
  69 inline namespace __cpo {
  70 inline constexpr auto partial_order = __partial_order::__fn{};
  71 } // namespace __cpo
  72
  73 #endif // _LIBCPP_STD_VER >= 20
  74
  75 _LIBCPP_END_NAMESPACE_STD
  76
  77 #endif // _LIBCPP___COMPARE_PARTIAL_ORDER