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_RBEGIN_H 11 #define _LIBCPP___RANGES_RBEGIN_H 12 13 #include <__concepts/class_or_enum.h> 14 #include <__concepts/same_as.h> 15 #include <__config> 16 #include <__iterator/concepts.h> 17 #include <__iterator/readable_traits.h> 18 #include <__iterator/reverse_iterator.h> 19 #include <__ranges/access.h> 20 #include <__type_traits/decay.h> 21 #include <__type_traits/is_reference.h> 22 #include <__type_traits/remove_cvref.h> 23 #include <__type_traits/remove_reference.h> 24 #include <__utility/auto_cast.h> 25 26 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 27 # pragma GCC system_header 28 #endif 29 30 _LIBCPP_BEGIN_NAMESPACE_STD 31 32 #if _LIBCPP_STD_VER >= 20 33 34 // [ranges.access.rbegin] 35 36 namespace ranges { 37 namespace __rbegin { 38 template <class _Tp> 39 concept __member_rbegin = 40 __can_borrow<_Tp> && 41 __workaround_52970<_Tp> && 42 requires(_Tp&& __t) { 43 { _LIBCPP_AUTO_CAST(__t.rbegin()) } -> input_or_output_iterator; 44 }; 45 46 void rbegin(auto&) = delete; 47 void rbegin(const auto&) = delete; 48 49 template <class _Tp> 50 concept __unqualified_rbegin = 51 !__member_rbegin<_Tp> && 52 __can_borrow<_Tp> && 53 __class_or_enum<remove_cvref_t<_Tp>> && 54 requires(_Tp&& __t) { 55 { _LIBCPP_AUTO_CAST(rbegin(__t)) } -> input_or_output_iterator; 56 }; 57 58 template <class _Tp> 59 concept __can_reverse = 60 __can_borrow<_Tp> && 61 !__member_rbegin<_Tp> && 62 !__unqualified_rbegin<_Tp> && 63 requires(_Tp&& __t) { 64 { ranges::begin(__t) } -> same_as<decltype(ranges::end(__t))>; 65 { ranges::begin(__t) } -> bidirectional_iterator; 66 }; 67 68 struct __fn { 69 template <class _Tp> 70 requires __member_rbegin<_Tp> 71 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const 72 noexcept(noexcept(_LIBCPP_AUTO_CAST(__t.rbegin()))) 73 { 74 return _LIBCPP_AUTO_CAST(__t.rbegin()); 75 } 76 77 template <class _Tp> 78 requires __unqualified_rbegin<_Tp> 79 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const 80 noexcept(noexcept(_LIBCPP_AUTO_CAST(rbegin(__t)))) 81 { 82 return _LIBCPP_AUTO_CAST(rbegin(__t)); 83 } 84 85 template <class _Tp> 86 requires __can_reverse<_Tp> 87 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const 88 noexcept(noexcept(ranges::end(__t))) 89 { 90 return std::make_reverse_iterator(ranges::end(__t)); 91 } 92 93 void operator()(auto&&) const = delete; 94 }; 95 } // namespace __rbegin 96 97 inline namespace __cpo { 98 inline constexpr auto rbegin = __rbegin::__fn{}; 99 } // namespace __cpo 100 } // namespace ranges 101 102 // [range.access.crbegin] 103 104 namespace ranges { 105 namespace __crbegin { 106 struct __fn { 107 template <class _Tp> 108 requires is_lvalue_reference_v<_Tp&&> 109 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI 110 constexpr auto operator()(_Tp&& __t) const 111 noexcept(noexcept(ranges::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t)))) 112 -> decltype( ranges::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t))) 113 { return ranges::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t)); } 114 115 template <class _Tp> 116 requires is_rvalue_reference_v<_Tp&&> 117 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI 118 constexpr auto operator()(_Tp&& __t) const 119 noexcept(noexcept(ranges::rbegin(static_cast<const _Tp&&>(__t)))) 120 -> decltype( ranges::rbegin(static_cast<const _Tp&&>(__t))) 121 { return ranges::rbegin(static_cast<const _Tp&&>(__t)); } 122 }; 123 } // namespace __crbegin 124 125 inline namespace __cpo { 126 inline constexpr auto crbegin = __crbegin::__fn{}; 127 } // namespace __cpo 128 } // namespace ranges 129 130 #endif // _LIBCPP_STD_VER >= 20 131 132 _LIBCPP_END_NAMESPACE_STD 133 134 #endif // _LIBCPP___RANGES_RBEGIN_H 135