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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_FILTER_VIEW_H
11#define _LIBCPP___RANGES_FILTER_VIEW_H
12
13#include <__algorithm/ranges_find_if.h>
14#include <__assert>
15#include <__concepts/constructible.h>
16#include <__concepts/copyable.h>
17#include <__concepts/derived_from.h>
18#include <__concepts/equality_comparable.h>
19#include <__config>
20#include <__functional/bind_back.h>
21#include <__functional/invoke.h>
22#include <__functional/reference_wrapper.h>
23#include <__iterator/concepts.h>
24#include <__iterator/iter_move.h>
25#include <__iterator/iter_swap.h>
26#include <__iterator/iterator_traits.h>
27#include <__memory/addressof.h>
28#include <__ranges/access.h>
29#include <__ranges/all.h>
30#include <__ranges/concepts.h>
31#include <__ranges/movable_box.h>
32#include <__ranges/non_propagating_cache.h>
33#include <__ranges/range_adaptor.h>
34#include <__ranges/view_interface.h>
35#include <__type_traits/conditional.h>
36#include <__type_traits/decay.h>
37#include <__type_traits/is_nothrow_constructible.h>
38#include <__type_traits/is_object.h>
39#include <__utility/forward.h>
40#include <__utility/in_place.h>
41#include <__utility/move.h>
42
43#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
44# pragma GCC system_header
45#endif
46
47_LIBCPP_PUSH_MACROS
48#include <__undef_macros>
49
50_LIBCPP_BEGIN_NAMESPACE_STD
51
52#if _LIBCPP_STD_VER >= 20
53
54namespace ranges {
55template <input_range _View, indirect_unary_predicate<iterator_t<_View>> _Pred>
56 requires view<_View> && is_object_v<_Pred>
57class _LIBCPP_ABI_LLVM18_NO_UNIQUE_ADDRESS filter_view : public view_interface<filter_view<_View, _Pred>> {
58 _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
59 _LIBCPP_NO_UNIQUE_ADDRESS __movable_box<_Pred> __pred_;
60
61 // We cache the result of begin() to allow providing an amortized O(1) begin() whenever
62 // the underlying range is at least a forward_range.
63 static constexpr bool _UseCache = forward_range<_View>;
64 using _Cache _LIBCPP_NODEBUG = _If<_UseCache, __non_propagating_cache<iterator_t<_View>>, __empty_cache>;
65 _LIBCPP_NO_UNIQUE_ADDRESS _Cache __cached_begin_ = _Cache();
66
67 class __iterator;
68 class __sentinel;
69
70public:
71 _LIBCPP_HIDE_FROM_ABI filter_view()
72 requires default_initializable<_View> && default_initializable<_Pred>
73 = default;
74
75 _LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX23 filter_view(_View __base, _Pred __pred)
76 : __base_(std::move(__base)), __pred_(in_place, std::move(__pred)) {}
77
78 template <class _Vp = _View>
79 _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
80 requires copy_constructible<_Vp>
81 {
82 return __base_;
83 }
84 _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
85
86 _LIBCPP_HIDE_FROM_ABI constexpr _Pred const& pred() const { return *__pred_; }
87
88 _LIBCPP_HIDE_FROM_ABI constexpr __iterator begin() {
89 // Note: this duplicates a check in `optional` but provides a better error message.
90 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
91 __pred_.__has_value(), "Trying to call begin() on a filter_view that does not have a valid predicate.");
92 if constexpr (_UseCache) {
93 if (!__cached_begin_.__has_value()) {
94 __cached_begin_.__emplace(ranges::find_if(__base_, std::ref(*__pred_)));
95 }
96 return {*this, *__cached_begin_};
97 } else {
98 return {*this, ranges::find_if(__base_, std::ref(*__pred_))};
99 }
100 }
101
102 _LIBCPP_HIDE_FROM_ABI constexpr auto end() {
103 if constexpr (common_range<_View>)
104 return __iterator{*this, ranges::end(__base_)};
105 else
106 return __sentinel{*this};
107 }
108};
109
110template <class _Range, class _Pred>
111filter_view(_Range&&, _Pred) -> filter_view<views::all_t<_Range>, _Pred>;
112
113template <class _View>
114struct __filter_iterator_category {};
115
116template <forward_range _View>
117struct __filter_iterator_category<_View> {
118 using _Cat _LIBCPP_NODEBUG = typename iterator_traits<iterator_t<_View>>::iterator_category;
119 using iterator_category =
120 _If<derived_from<_Cat, bidirectional_iterator_tag>,
121 bidirectional_iterator_tag,
122 _If<derived_from<_Cat, forward_iterator_tag>,
123 forward_iterator_tag,
124 /* else */ _Cat >>;
125};
126
127template <input_range _View, indirect_unary_predicate<iterator_t<_View>> _Pred>
128 requires view<_View> && is_object_v<_Pred>
129class filter_view<_View, _Pred>::__iterator : public __filter_iterator_category<_View> {
130public:
131 _LIBCPP_NO_UNIQUE_ADDRESS iterator_t<_View> __current_ = iterator_t<_View>();
132 _LIBCPP_NO_UNIQUE_ADDRESS filter_view* __parent_ = nullptr;
133
134 using iterator_concept =
135 _If<bidirectional_range<_View>,
136 bidirectional_iterator_tag,
137 _If<forward_range<_View>,
138 forward_iterator_tag,
139 /* else */ input_iterator_tag >>;
140 // using iterator_category = inherited;
141 using value_type = range_value_t<_View>;
142 using difference_type = range_difference_t<_View>;
143
144 _LIBCPP_HIDE_FROM_ABI __iterator()
145 requires default_initializable<iterator_t<_View>>
146 = default;
147
148 _LIBCPP_HIDE_FROM_ABI constexpr __iterator(filter_view& __parent, iterator_t<_View> __current)
149 : __current_(std::move(__current)), __parent_(std::addressof(__parent)) {}
150
151 _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_View> const& base() const& noexcept { return __current_; }
152 _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_View> base() && { return std::move(__current_); }
153
154 _LIBCPP_HIDE_FROM_ABI constexpr range_reference_t<_View> operator*() const { return *__current_; }
155 _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_View> operator->() const
156 requires __has_arrow<iterator_t<_View>> && copyable<iterator_t<_View>>
157 {
158 return __current_;
159 }
160
161 _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator++() {
162 __current_ =
163 ranges::find_if(std::move(++__current_), ranges::end(__parent_->__base_), std::ref(*__parent_->__pred_));
164 return *this;
165 }
166 _LIBCPP_HIDE_FROM_ABI constexpr void operator++(int) { ++*this; }
167 _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator++(int)
168 requires forward_range<_View>
169 {
170 auto __tmp = *this;
171 ++*this;
172 return __tmp;
173 }
174
175 _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator--()
176 requires bidirectional_range<_View>
177 {
178 do {
179 --__current_;
180 } while (!std::invoke(*__parent_->__pred_, *__current_));
181 return *this;
182 }
183 _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator--(int)
184 requires bidirectional_range<_View>
185 {
186 auto __tmp = *this;
187 --*this;
188 return __tmp;
189 }
190
191 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(__iterator const& __x, __iterator const& __y)
192 requires equality_comparable<iterator_t<_View>>
193 {
194 return __x.__current_ == __y.__current_;
195 }
196
197 _LIBCPP_HIDE_FROM_ABI friend constexpr range_rvalue_reference_t<_View>
198 iter_move(__iterator const& __it) noexcept(noexcept(ranges::iter_move(__it.__current_))) {
199 return ranges::iter_move(__it.__current_);
200 }
201
202 _LIBCPP_HIDE_FROM_ABI friend constexpr void
203 iter_swap(__iterator const& __x,
204 __iterator const& __y) noexcept(noexcept(ranges::iter_swap(__x.__current_, __y.__current_)))
205 requires indirectly_swappable<iterator_t<_View>>
206 {
207 return ranges::iter_swap(__x.__current_, __y.__current_);
208 }
209};
210
211template <input_range _View, indirect_unary_predicate<iterator_t<_View>> _Pred>
212 requires view<_View> && is_object_v<_Pred>
213class filter_view<_View, _Pred>::__sentinel {
214public:
215 sentinel_t<_View> __end_ = sentinel_t<_View>();
216
217 _LIBCPP_HIDE_FROM_ABI __sentinel() = default;
218
219 _LIBCPP_HIDE_FROM_ABI constexpr explicit __sentinel(filter_view& __parent) : __end_(ranges::end(__parent.__base_)) {}
220
221 _LIBCPP_HIDE_FROM_ABI constexpr sentinel_t<_View> base() const { return __end_; }
222
223 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(__iterator const& __x, __sentinel const& __y) {
224 return __x.__current_ == __y.__end_;
225 }
226};
227
228namespace views {
229namespace __filter {
230struct __fn {
231 template <class _Range, class _Pred>
232 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Pred&& __pred) const
233 noexcept(noexcept(filter_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))))
234 -> decltype(filter_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))) {
235 return filter_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred));
236 }
237
238 template <class _Pred>
239 requires constructible_from<decay_t<_Pred>, _Pred>
240 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Pred&& __pred) const
241 noexcept(is_nothrow_constructible_v<decay_t<_Pred>, _Pred>) {
242 return __pipeable(std::__bind_back(*this, std::forward<_Pred>(__pred)));
243 }
244};
245} // namespace __filter
246
247inline namespace __cpo {
248inline constexpr auto filter = __filter::__fn{};
249} // namespace __cpo
250} // namespace views
251
252} // namespace ranges
253
254#endif // _LIBCPP_STD_VER >= 20
255
256_LIBCPP_END_NAMESPACE_STD
257
258_LIBCPP_POP_MACROS
259
260#endif // _LIBCPP___RANGES_FILTER_VIEW_H
261

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source code of libcxx/include/__ranges/filter_view.h