__cxx03/__iterator/unreachable_sentinel.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___CXX03___ITERATOR_UNREACHABLE_SENTINEL_H
0011 #define _LIBCPP___CXX03___ITERATOR_UNREACHABLE_SENTINEL_H
0012
0013 #include <__cxx03/__config>
0014 #include <__cxx03/__iterator/concepts.h>
0015
0016 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0017 #  pragma GCC system_header
0018 #endif
0019
0020 _LIBCPP_BEGIN_NAMESPACE_STD
0021
0022 #if _LIBCPP_STD_VER >= 20
0023
0024 struct unreachable_sentinel_t {
0025   template <weakly_incrementable _Iter>
0026   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(unreachable_sentinel_t, const _Iter&) noexcept {
0027     return false;
0028   }
0029 };
0030
0031 inline constexpr unreachable_sentinel_t unreachable_sentinel{};
0032
0033 #endif // _LIBCPP_STD_VER >= 20
0034
0035 _LIBCPP_END_NAMESPACE_STD
0036
0037 #endif // _LIBCPP___CXX03___ITERATOR_UNREACHABLE_SENTINEL_H