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 26 template <class _It, class _Proj> 27 struct __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 34 template <weakly_incrementable _It, class _Proj> 35 struct __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). 46 template <indirectly_readable _It, indirectly_regular_unary_invocable<_It> _Proj> 47 using 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