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