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 = __can_borrow<_Tp> && __workaround_52970<_Tp> && requires(_Tp&& __t) { 40 { _LIBCPP_AUTO_CAST(__t.rbegin()) } -> input_or_output_iterator; 41 }; 42 43 void rbegin(auto&) = delete; 44 void rbegin(const auto&) = delete; 45 46 template <class _Tp> 47 concept __unqualified_rbegin = 48 !__member_rbegin<_Tp> && __can_borrow<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) { 49 { _LIBCPP_AUTO_CAST(rbegin(__t)) } -> input_or_output_iterator; 50 }; 51 52 template <class _Tp> 53 concept __can_reverse = 54 __can_borrow<_Tp> && !__member_rbegin<_Tp> && !__unqualified_rbegin<_Tp> && requires(_Tp&& __t) { 55 { ranges::begin(__t) } -> same_as<decltype(ranges::end(__t))>; 56 { ranges::begin(__t) } -> bidirectional_iterator; 57 }; 58 59 struct __fn { 60 template <class _Tp> 61 requires __member_rbegin<_Tp> 62 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const 63 noexcept(noexcept(_LIBCPP_AUTO_CAST(__t.rbegin()))) { 64 return _LIBCPP_AUTO_CAST(__t.rbegin()); 65 } 66 67 template <class _Tp> 68 requires __unqualified_rbegin<_Tp> 69 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const 70 noexcept(noexcept(_LIBCPP_AUTO_CAST(rbegin(__t)))) { 71 return _LIBCPP_AUTO_CAST(rbegin(__t)); 72 } 73 74 template <class _Tp> 75 requires __can_reverse<_Tp> 76 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const noexcept(noexcept(ranges::end(__t))) { 77 return std::make_reverse_iterator(ranges::end(__t)); 78 } 79 80 void operator()(auto&&) const = delete; 81 }; 82 } // namespace __rbegin 83 84 inline namespace __cpo { 85 inline constexpr auto rbegin = __rbegin::__fn{}; 86 } // namespace __cpo 87 } // namespace ranges 88 89 // [range.access.crbegin] 90 91 namespace ranges { 92 namespace __crbegin { 93 struct __fn { 94 template <class _Tp> 95 requires is_lvalue_reference_v<_Tp&&> 96 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const 97 noexcept(noexcept(ranges::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t)))) 98 -> decltype(ranges::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t))) { 99 return ranges::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t)); 100 } 101 102 template <class _Tp> 103 requires is_rvalue_reference_v<_Tp&&> 104 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const 105 noexcept(noexcept(ranges::rbegin(static_cast<const _Tp&&>(__t)))) 106 -> decltype(ranges::rbegin(static_cast<const _Tp&&>(__t))) { 107 return ranges::rbegin(static_cast<const _Tp&&>(__t)); 108 } 109 }; 110 } // namespace __crbegin 111 112 inline namespace __cpo { 113 inline constexpr auto crbegin = __crbegin::__fn{}; 114 } // namespace __cpo 115 } // namespace ranges 116 117 #endif // _LIBCPP_STD_VER >= 20 118 119 _LIBCPP_END_NAMESPACE_STD 120 121 #endif // _LIBCPP___RANGES_RBEGIN_H 122