libcxx/include/__iterator/projected.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 #ifndef _LIBCPP___ITERATOR_PROJECTED_H
  10 #define _LIBCPP___ITERATOR_PROJECTED_H
  11
  12 #include <__config>
  13 #include <__iterator/concepts.h>
  14 #include <__iterator/incrementable_traits.h>
  15 #include <type_traits>
  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 !defined(_LIBCPP_HAS_NO_RANGES)
  24
  25 template<indirectly_readable _It, indirectly_regular_unary_invocable<_It> _Proj>
  26 struct projected {
  27   using value_type = remove_cvref_t<indirect_result_t<_Proj&, _It>>;
  28   indirect_result_t<_Proj&, _It> operator*() const; // not defined
  29 };
  30
  31 template<weakly_incrementable _It, class _Proj>
  32 struct incrementable_traits<projected<_It, _Proj>> {
  33   using difference_type = iter_difference_t<_It>;
  34 };
  35
  36 #endif // !defined(_LIBCPP_HAS_NO_RANGES)
  37
  38 _LIBCPP_END_NAMESPACE_STD
  39
  40 #endif // _LIBCPP___ITERATOR_PROJECTED_H