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_PROJECTED_H 11#define _LIBCPP___ITERATOR_PROJECTED_H 12 13#include <__config> 14#include <__iterator/concepts.h> 15#include <__iterator/incrementable_traits.h> // iter_difference_t 16#include <__type_traits/remove_cvref.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 26template <class _It, class _Proj> 27struct __projected_impl { 28 struct __type { 29 using value_type = remove_cvref_t<indirect_result_t<_Proj&, _It>>; 30 indirect_result_t<_Proj&, _It> operator*() const; // not defined 31 }; 32}; 33 34template <weakly_incrementable _It, class _Proj> 35struct __projected_impl<_It, _Proj> { 36 struct __type { 37 using value_type = remove_cvref_t<indirect_result_t<_Proj&, _It>>; 38 using difference_type = iter_difference_t<_It>; 39 indirect_result_t<_Proj&, _It> operator*() const; // not defined 40 }; 41}; 42 43// Note that we implement std::projected in a way that satisfies P2538R1 even in standard 44// modes before C++26 to avoid breaking the ABI between standard modes (even though ABI 45// breaks with std::projected are expected to have essentially no impact). 46template <indirectly_readable _It, indirectly_regular_unary_invocable<_It> _Proj> 47using projected = typename __projected_impl<_It, _Proj>::__type; 48 49#endif // _LIBCPP_STD_VER >= 20 50 51_LIBCPP_END_NAMESPACE_STD 52 53#endif // _LIBCPP___ITERATOR_PROJECTED_H 54