libcxx/include/__compare/compare_three_way.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___COMPARE_COMPARE_THREE_WAY_H
  11 #define _LIBCPP___COMPARE_COMPARE_THREE_WAY_H
  12
  13 #include <__compare/three_way_comparable.h>
  14 #include <__config>
  15 #include <__utility/forward.h>
  16
  17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  18 #  pragma GCC system_header
  19 #endif
  20
  21 _LIBCPP_BEGIN_NAMESPACE_STD
  22
  23 #if _LIBCPP_STD_VER >= 20
  24
  25 struct _LIBCPP_TEMPLATE_VIS compare_three_way {
  26   template <class _T1, class _T2>
  27     requires three_way_comparable_with<_T1, _T2>
  28   constexpr _LIBCPP_HIDE_FROM_ABI auto operator()(_T1&& __t, _T2&& __u) const
  29       noexcept(noexcept(std::forward<_T1>(__t) <=> std::forward<_T2>(__u))) {
  30     return std::forward<_T1>(__t) <=> std::forward<_T2>(__u);
  31   }
  32
  33   using is_transparent = void;
  34 };
  35
  36 #endif // _LIBCPP_STD_VER >= 20
  37
  38 _LIBCPP_END_NAMESPACE_STD
  39
  40 #endif // _LIBCPP___COMPARE_COMPARE_THREE_WAY_H