libcxx/include/__ranges/dangling.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___RANGES_DANGLING_H
  11 #define _LIBCPP___RANGES_DANGLING_H
  12
  13 #include <__config>
  14 #include <__ranges/access.h>
  15 #include <__ranges/concepts.h>
  16 #include <__type_traits/conditional.h>
  17
  18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  19 #  pragma GCC system_header
  20 #endif
  21
  22 _LIBCPP_BEGIN_NAMESPACE_STD
  23
  24 #if _LIBCPP_STD_VER >= 20
  25
  26 namespace ranges {
  27 struct dangling {
  28   dangling() = default;
  29   _LIBCPP_HIDE_FROM_ABI constexpr dangling(auto&&...) noexcept {}
  30 };
  31
  32 template <range _Rp>
  33 using borrowed_iterator_t = _If<borrowed_range<_Rp>, iterator_t<_Rp>, dangling>;
  34
  35 // borrowed_subrange_t defined in <__ranges/subrange.h>
  36 } // namespace ranges
  37
  38 #endif // _LIBCPP_STD_VER >= 20
  39
  40 _LIBCPP_END_NAMESPACE_STD
  41
  42 #endif // _LIBCPP___RANGES_DANGLING_H