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