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_ELEMENTS_VIEW_H
11 #define _LIBCPP___RANGES_ELEMENTS_VIEW_H
12 
13 #include <__compare/three_way_comparable.h>
14 #include <__concepts/constructible.h>
15 #include <__concepts/convertible_to.h>
16 #include <__concepts/derived_from.h>
17 #include <__concepts/equality_comparable.h>
18 #include <__config>
19 #include <__fwd/get.h>
20 #include <__iterator/concepts.h>
21 #include <__iterator/iterator_traits.h>
22 #include <__ranges/access.h>
23 #include <__ranges/all.h>
24 #include <__ranges/concepts.h>
25 #include <__ranges/enable_borrowed_range.h>
26 #include <__ranges/range_adaptor.h>
27 #include <__ranges/size.h>
28 #include <__ranges/view_interface.h>
29 #include <__tuple/tuple_element.h>
30 #include <__tuple/tuple_like.h>
31 #include <__tuple/tuple_size.h>
32 #include <__type_traits/is_reference.h>
33 #include <__type_traits/maybe_const.h>
34 #include <__type_traits/remove_cv.h>
35 #include <__type_traits/remove_cvref.h>
36 #include <__type_traits/remove_reference.h>
37 #include <__utility/declval.h>
38 #include <__utility/forward.h>
39 #include <__utility/move.h>
40 #include <cstddef>
41 
42 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
43 #  pragma GCC system_header
44 #endif
45 
46 _LIBCPP_PUSH_MACROS
47 #include <__undef_macros>
48 
49 _LIBCPP_BEGIN_NAMESPACE_STD
50 
51 #if _LIBCPP_STD_VER >= 20
52 
53 namespace ranges {
54 
55 template <class _Tp, size_t _Np>
56 concept __has_tuple_element = __tuple_like<_Tp> && _Np < tuple_size<_Tp>::value;
57 
58 template <class _Tp, size_t _Np>
59 concept __returnable_element = is_reference_v<_Tp> || move_constructible<tuple_element_t<_Np, _Tp>>;
60 
61 template <input_range _View, size_t _Np>
62   requires view<_View> && __has_tuple_element<range_value_t<_View>, _Np> &&
63            __has_tuple_element<remove_reference_t<range_reference_t<_View>>, _Np> &&
64            __returnable_element<range_reference_t<_View>, _Np>
65 class elements_view : public view_interface<elements_view<_View, _Np>> {
66 private:
67   template <bool>
68   class __iterator;
69 
70   template <bool>
71   class __sentinel;
72 
73 public:
74   _LIBCPP_HIDE_FROM_ABI elements_view()
75     requires default_initializable<_View>
76   = default;
77 
78   _LIBCPP_HIDE_FROM_ABI constexpr explicit elements_view(_View __base) : __base_(std::move(__base)) {}
79 
80   _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
81     requires copy_constructible<_View>
82   {
83     return __base_;
84   }
85 
86   _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
87 
88   _LIBCPP_HIDE_FROM_ABI constexpr auto begin()
89     requires(!__simple_view<_View>)
90   {
91     return __iterator</*_Const=*/false>(ranges::begin(__base_));
92   }
93 
94   _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
95     requires range<const _View>
96   {
97     return __iterator</*_Const=*/true>(ranges::begin(__base_));
98   }
99 
100   _LIBCPP_HIDE_FROM_ABI constexpr auto end()
101     requires(!__simple_view<_View> && !common_range<_View>)
102   {
103     return __sentinel</*_Const=*/false>{ranges::end(__base_)};
104   }
105 
106   _LIBCPP_HIDE_FROM_ABI constexpr auto end()
107     requires(!__simple_view<_View> && common_range<_View>)
108   {
109     return __iterator</*_Const=*/false>{ranges::end(__base_)};
110   }
111 
112   _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
113     requires range<const _View>
114   {
115     return __sentinel</*_Const=*/true>{ranges::end(__base_)};
116   }
117 
118   _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
119     requires common_range<const _View>
120   {
121     return __iterator</*_Const=*/true>{ranges::end(__base_)};
122   }
123 
124   _LIBCPP_HIDE_FROM_ABI constexpr auto size()
125     requires sized_range<_View>
126   {
127     return ranges::size(__base_);
128   }
129 
130   _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
131     requires sized_range<const _View>
132   {
133     return ranges::size(__base_);
134   }
135 
136 private:
137   _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
138 };
139 
140 template <class, size_t>
141 struct __elements_view_iterator_category_base {};
142 
143 template <forward_range _Base, size_t _Np>
144 struct __elements_view_iterator_category_base<_Base, _Np> {
145   static consteval auto __get_iterator_category() {
146     using _Result = decltype(std::get<_Np>(*std::declval<iterator_t<_Base>>()));
147     using _Cat    = typename iterator_traits<iterator_t<_Base>>::iterator_category;
148 
149     if constexpr (!is_lvalue_reference_v<_Result>) {
150       return input_iterator_tag{};
151     } else if constexpr (derived_from<_Cat, random_access_iterator_tag>) {
152       return random_access_iterator_tag{};
153     } else {
154       return _Cat{};
155     }
156   }
157 
158   using iterator_category = decltype(__get_iterator_category());
159 };
160 
161 template <input_range _View, size_t _Np>
162   requires view<_View> && __has_tuple_element<range_value_t<_View>, _Np> &&
163            __has_tuple_element<remove_reference_t<range_reference_t<_View>>, _Np> &&
164            __returnable_element<range_reference_t<_View>, _Np>
165 template <bool _Const>
166 class elements_view<_View, _Np>::__iterator
167     : public __elements_view_iterator_category_base<__maybe_const<_Const, _View>, _Np> {
168   template <bool>
169   friend class __iterator;
170 
171   template <bool>
172   friend class __sentinel;
173 
174   using _Base = __maybe_const<_Const, _View>;
175 
176   iterator_t<_Base> __current_ = iterator_t<_Base>();
177 
178   _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __get_element(const iterator_t<_Base>& __i) {
179     if constexpr (is_reference_v<range_reference_t<_Base>>) {
180       return std::get<_Np>(*__i);
181     } else {
182       using _Element = remove_cv_t<tuple_element_t<_Np, range_reference_t<_Base>>>;
183       return static_cast<_Element>(std::get<_Np>(*__i));
184     }
185   }
186 
187   static consteval auto __get_iterator_concept() {
188     if constexpr (random_access_range<_Base>) {
189       return random_access_iterator_tag{};
190     } else if constexpr (bidirectional_range<_Base>) {
191       return bidirectional_iterator_tag{};
192     } else if constexpr (forward_range<_Base>) {
193       return forward_iterator_tag{};
194     } else {
195       return input_iterator_tag{};
196     }
197   }
198 
199 public:
200   using iterator_concept = decltype(__get_iterator_concept());
201   using value_type       = remove_cvref_t<tuple_element_t<_Np, range_value_t<_Base>>>;
202   using difference_type  = range_difference_t<_Base>;
203 
204   _LIBCPP_HIDE_FROM_ABI __iterator()
205     requires default_initializable<iterator_t<_Base>>
206   = default;
207 
208   _LIBCPP_HIDE_FROM_ABI constexpr explicit __iterator(iterator_t<_Base> __current) : __current_(std::move(__current)) {}
209 
210   _LIBCPP_HIDE_FROM_ABI constexpr __iterator(__iterator<!_Const> __i)
211     requires _Const && convertible_to<iterator_t<_View>, iterator_t<_Base>>
212       : __current_(std::move(__i.__current_)) {}
213 
214   _LIBCPP_HIDE_FROM_ABI constexpr const iterator_t<_Base>& base() const& noexcept { return __current_; }
215 
216   _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_Base> base() && { return std::move(__current_); }
217 
218   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() const { return __get_element(__current_); }
219 
220   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator++() {
221     ++__current_;
222     return *this;
223   }
224 
225   _LIBCPP_HIDE_FROM_ABI constexpr void operator++(int) { ++__current_; }
226 
227   _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator++(int)
228     requires forward_range<_Base>
229   {
230     auto __temp = *this;
231     ++__current_;
232     return __temp;
233   }
234 
235   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator--()
236     requires bidirectional_range<_Base>
237   {
238     --__current_;
239     return *this;
240   }
241 
242   _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator--(int)
243     requires bidirectional_range<_Base>
244   {
245     auto __temp = *this;
246     --__current_;
247     return __temp;
248   }
249 
250   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator+=(difference_type __n)
251     requires random_access_range<_Base>
252   {
253     __current_ += __n;
254     return *this;
255   }
256 
257   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator-=(difference_type __n)
258     requires random_access_range<_Base>
259   {
260     __current_ -= __n;
261     return *this;
262   }
263 
264   _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator[](difference_type __n) const
265     requires random_access_range<_Base>
266   {
267     return __get_element(__current_ + __n);
268   }
269 
270   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator& __x, const __iterator& __y)
271     requires equality_comparable<iterator_t<_Base>>
272   {
273     return __x.__current_ == __y.__current_;
274   }
275 
276   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<(const __iterator& __x, const __iterator& __y)
277     requires random_access_range<_Base>
278   {
279     return __x.__current_ < __y.__current_;
280   }
281 
282   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>(const __iterator& __x, const __iterator& __y)
283     requires random_access_range<_Base>
284   {
285     return __y < __x;
286   }
287 
288   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<=(const __iterator& __x, const __iterator& __y)
289     requires random_access_range<_Base>
290   {
291     return !(__y < __x);
292   }
293 
294   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>=(const __iterator& __x, const __iterator& __y)
295     requires random_access_range<_Base>
296   {
297     return !(__x < __y);
298   }
299 
300   _LIBCPP_HIDE_FROM_ABI friend constexpr auto operator<=>(const __iterator& __x, const __iterator& __y)
301     requires random_access_range<_Base> && three_way_comparable<iterator_t<_Base>>
302   {
303     return __x.__current_ <=> __y.__current_;
304   }
305 
306   _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator+(const __iterator& __x, difference_type __y)
307     requires random_access_range<_Base>
308   {
309     return __iterator{__x} += __y;
310   }
311 
312   _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator+(difference_type __x, const __iterator& __y)
313     requires random_access_range<_Base>
314   {
315     return __y + __x;
316   }
317 
318   _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator-(const __iterator& __x, difference_type __y)
319     requires random_access_range<_Base>
320   {
321     return __iterator{__x} -= __y;
322   }
323 
324   _LIBCPP_HIDE_FROM_ABI friend constexpr difference_type operator-(const __iterator& __x, const __iterator& __y)
325     requires sized_sentinel_for<iterator_t<_Base>, iterator_t<_Base>>
326   {
327     return __x.__current_ - __y.__current_;
328   }
329 };
330 
331 template <input_range _View, size_t _Np>
332   requires view<_View> && __has_tuple_element<range_value_t<_View>, _Np> &&
333            __has_tuple_element<remove_reference_t<range_reference_t<_View>>, _Np> &&
334            __returnable_element<range_reference_t<_View>, _Np>
335 template <bool _Const>
336 class elements_view<_View, _Np>::__sentinel {
337 private:
338   using _Base                                        = __maybe_const<_Const, _View>;
339   _LIBCPP_NO_UNIQUE_ADDRESS sentinel_t<_Base> __end_ = sentinel_t<_Base>();
340 
341   template <bool>
342   friend class __sentinel;
343 
344   template <bool _AnyConst>
345   _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __get_current(const __iterator<_AnyConst>& __iter) {
346     return (__iter.__current_);
347   }
348 
349 public:
350   _LIBCPP_HIDE_FROM_ABI __sentinel() = default;
351 
352   _LIBCPP_HIDE_FROM_ABI constexpr explicit __sentinel(sentinel_t<_Base> __end) : __end_(std::move(__end)) {}
353 
354   _LIBCPP_HIDE_FROM_ABI constexpr __sentinel(__sentinel<!_Const> __other)
355     requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>>
356       : __end_(std::move(__other.__end_)) {}
357 
358   _LIBCPP_HIDE_FROM_ABI constexpr sentinel_t<_Base> base() const { return __end_; }
359 
360   template <bool _OtherConst>
361     requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
362   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
363     return __get_current(__x) == __y.__end_;
364   }
365 
366   template <bool _OtherConst>
367     requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
368   _LIBCPP_HIDE_FROM_ABI friend constexpr range_difference_t<__maybe_const<_OtherConst, _View>>
369   operator-(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
370     return __get_current(__x) - __y.__end_;
371   }
372 
373   template <bool _OtherConst>
374     requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
375   _LIBCPP_HIDE_FROM_ABI friend constexpr range_difference_t<__maybe_const<_OtherConst, _View>>
376   operator-(const __sentinel& __x, const __iterator<_OtherConst>& __y) {
377     return __x.__end_ - __get_current(__y);
378   }
379 };
380 
381 template <class _Tp, size_t _Np>
382 inline constexpr bool enable_borrowed_range<elements_view<_Tp, _Np>> = enable_borrowed_range<_Tp>;
383 
384 template <class _Tp>
385 using keys_view = elements_view<_Tp, 0>;
386 template <class _Tp>
387 using values_view = elements_view<_Tp, 1>;
388 
389 namespace views {
390 namespace __elements {
391 
392 template <size_t _Np>
393 struct __fn : __range_adaptor_closure<__fn<_Np>> {
394   template <class _Range>
395   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range) const
396       /**/ noexcept(noexcept(elements_view<all_t<_Range&&>, _Np>(std::forward<_Range>(__range))))
397       /*------*/ -> decltype(elements_view<all_t<_Range&&>, _Np>(std::forward<_Range>(__range))) {
398     /*-------------*/ return elements_view<all_t<_Range&&>, _Np>(std::forward<_Range>(__range));
399   }
400 };
401 } // namespace __elements
402 
403 inline namespace __cpo {
404 template <size_t _Np>
405 inline constexpr auto elements = __elements::__fn<_Np>{};
406 inline constexpr auto keys     = elements<0>;
407 inline constexpr auto values   = elements<1>;
408 } // namespace __cpo
409 } // namespace views
410 } // namespace ranges
411 
412 #endif // _LIBCPP_STD_VER >= 20
413 
414 _LIBCPP_END_NAMESPACE_STD
415 
416 _LIBCPP_POP_MACROS
417 
418 #endif // _LIBCPP___RANGES_ELEMENTS_VIEW_H
419