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
36namespace ranges {
37namespace __rbegin {
38template <class _Tp>
39concept __member_rbegin = __can_borrow<_Tp> && __workaround_52970<_Tp> && requires(_Tp&& __t) {
40  { _LIBCPP_AUTO_CAST(__t.rbegin()) } -> input_or_output_iterator;
41};
42
43void rbegin(auto&)       = delete;
44void rbegin(const auto&) = delete;
45
46template <class _Tp>
47concept __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
52template <class _Tp>
53concept __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
59struct __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
84inline namespace __cpo {
85inline constexpr auto rbegin = __rbegin::__fn{};
86} // namespace __cpo
87} // namespace ranges
88
89// [range.access.crbegin]
90
91namespace ranges {
92namespace __crbegin {
93struct __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
112inline namespace __cpo {
113inline 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