libcxx/include/__iterator/unreachable_sentinel.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___ITERATOR_UNREACHABLE_SENTINEL_H
  11 #define _LIBCPP___ITERATOR_UNREACHABLE_SENTINEL_H
  12
  13 #include <__config>
  14 #include <__iterator/concepts.h>
  15
  16 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  17 #  pragma GCC system_header
  18 #endif
  19
  20 _LIBCPP_BEGIN_NAMESPACE_STD
  21
  22 #if _LIBCPP_STD_VER >= 20
  23
  24 struct unreachable_sentinel_t {
  25   template <weakly_incrementable _Iter>
  26   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(unreachable_sentinel_t, const _Iter&) noexcept {
  27     return false;
  28   }
  29 };
  30
  31 inline constexpr unreachable_sentinel_t unreachable_sentinel{};
  32
  33 #endif // _LIBCPP_STD_VER >= 20
  34
  35 _LIBCPP_END_NAMESPACE_STD
  36
  37 #endif // _LIBCPP___ITERATOR_UNREACHABLE_SENTINEL_H