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