1 // Concepts and traits for use with iterators -*- C++ -*-
2
3 // Copyright (C) 2019-2021 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24
25 /** @file bits/iterator_concepts.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{iterator}
28 */
29
30 #ifndef _ITERATOR_CONCEPTS_H
31 #define _ITERATOR_CONCEPTS_H 1
32
33 #pragma GCC system_header
34
35 #include <concepts>
36 #include <bits/ptr_traits.h> // to_address
37 #include <bits/ranges_cmp.h> // identity, ranges::less
38
39 #if __cpp_lib_concepts
_GLIBCXX_VISIBILITY(default)40 namespace std _GLIBCXX_VISIBILITY(default)
41 {
42 _GLIBCXX_BEGIN_NAMESPACE_VERSION
43
44 struct input_iterator_tag;
45 struct output_iterator_tag;
46 struct forward_iterator_tag;
47 struct bidirectional_iterator_tag;
48 struct random_access_iterator_tag;
49 struct contiguous_iterator_tag;
50
51 template<typename _Iterator>
52 struct iterator_traits;
53
54 template<typename _Tp> requires is_object_v<_Tp>
55 struct iterator_traits<_Tp*>;
56
57 template<typename _Iterator, typename>
58 struct __iterator_traits;
59
60 namespace __detail
61 {
62 template<typename _Tp>
63 using __with_ref = _Tp&;
64
65 template<typename _Tp>
66 concept __can_reference = requires { typename __with_ref<_Tp>; };
67
68 template<typename _Tp>
69 concept __dereferenceable = requires(_Tp& __t)
70 {
71 { *__t } -> __can_reference;
72 };
73 } // namespace __detail
74
75 template<__detail::__dereferenceable _Tp>
76 using iter_reference_t = decltype(*std::declval<_Tp&>());
77
78 namespace ranges
79 {
80 namespace __cust_imove
81 {
82 void iter_move();
83
84 template<typename _Tp>
85 concept __adl_imove
86 = (std::__detail::__class_or_enum<remove_reference_t<_Tp>>)
87 && requires(_Tp&& __t) { iter_move(static_cast<_Tp&&>(__t)); };
88
89 struct _IMove
90 {
91 private:
92 template<typename _Tp>
93 struct __result
94 { using type = iter_reference_t<_Tp>; };
95
96 template<typename _Tp>
97 requires __adl_imove<_Tp>
98 struct __result<_Tp>
99 { using type = decltype(iter_move(std::declval<_Tp>())); };
100
101 template<typename _Tp>
102 requires (!__adl_imove<_Tp>)
103 && is_lvalue_reference_v<iter_reference_t<_Tp>>
104 struct __result<_Tp>
105 { using type = remove_reference_t<iter_reference_t<_Tp>>&&; };
106
107 template<typename _Tp>
108 static constexpr bool
109 _S_noexcept()
110 {
111 if constexpr (__adl_imove<_Tp>)
112 return noexcept(iter_move(std::declval<_Tp>()));
113 else
114 return noexcept(*std::declval<_Tp>());
115 }
116
117 public:
118 // The result type of iter_move(std::declval<_Tp>())
119 template<std::__detail::__dereferenceable _Tp>
120 using __type = typename __result<_Tp>::type;
121
122 template<std::__detail::__dereferenceable _Tp>
123 constexpr __type<_Tp>
124 operator()(_Tp&& __e) const
125 noexcept(_S_noexcept<_Tp>())
126 {
127 if constexpr (__adl_imove<_Tp>)
128 return iter_move(static_cast<_Tp&&>(__e));
129 else if constexpr (is_lvalue_reference_v<iter_reference_t<_Tp>>)
130 return static_cast<__type<_Tp>>(*__e);
131 else
132 return *__e;
133 }
134 };
135 } // namespace __cust_imove
136
137 inline namespace __cust
138 {
139 inline constexpr __cust_imove::_IMove iter_move{};
140 } // inline namespace __cust
141 } // namespace ranges
142
143 template<__detail::__dereferenceable _Tp>
144 requires __detail::
145 __can_reference<ranges::__cust_imove::_IMove::__type<_Tp&>>
146 using iter_rvalue_reference_t
147 = ranges::__cust_imove::_IMove::__type<_Tp&>;
148
149 template<typename> struct incrementable_traits { };
150
151 template<typename _Tp> requires is_object_v<_Tp>
152 struct incrementable_traits<_Tp*>
153 { using difference_type = ptrdiff_t; };
154
155 template<typename _Iter>
156 struct incrementable_traits<const _Iter>
157 : incrementable_traits<_Iter> { };
158
159 template<typename _Tp> requires requires { typename _Tp::difference_type; }
160 struct incrementable_traits<_Tp>
161 { using difference_type = typename _Tp::difference_type; };
162
163 template<typename _Tp>
164 requires (!requires { typename _Tp::difference_type; }
165 && requires(const _Tp& __a, const _Tp& __b)
166 { { __a - __b } -> integral; })
167 struct incrementable_traits<_Tp>
168 {
169 using difference_type
170 = make_signed_t<decltype(std::declval<_Tp>() - std::declval<_Tp>())>;
171 };
172
173 #if defined __STRICT_ANSI__ && defined __SIZEOF_INT128__
174 // __int128 is incrementable even if !integral<__int128>
175 template<>
176 struct incrementable_traits<__int128>
177 { using difference_type = __int128; };
178
179 template<>
180 struct incrementable_traits<unsigned __int128>
181 { using difference_type = __int128; };
182 #endif
183
184 namespace __detail
185 {
186 // An iterator such that iterator_traits<_Iter> names a specialization
187 // generated from the primary template.
188 template<typename _Iter>
189 concept __primary_traits_iter
190 = __is_base_of(__iterator_traits<_Iter, void>, iterator_traits<_Iter>);
191
192 template<typename _Iter, typename _Tp>
193 struct __iter_traits_impl
194 { using type = iterator_traits<_Iter>; };
195
196 template<typename _Iter, typename _Tp>
197 requires __primary_traits_iter<_Iter>
198 struct __iter_traits_impl<_Iter, _Tp>
199 { using type = _Tp; };
200
201 // ITER_TRAITS
202 template<typename _Iter, typename _Tp = _Iter>
203 using __iter_traits = typename __iter_traits_impl<_Iter, _Tp>::type;
204
205 template<typename _Tp>
206 using __iter_diff_t = typename
207 __iter_traits<_Tp, incrementable_traits<_Tp>>::difference_type;
208 } // namespace __detail
209
210 template<typename _Tp>
211 using iter_difference_t = __detail::__iter_diff_t<remove_cvref_t<_Tp>>;
212
213 namespace __detail
214 {
215 template<typename> struct __cond_value_type { };
216
217 template<typename _Tp> requires is_object_v<_Tp>
218 struct __cond_value_type<_Tp>
219 { using value_type = remove_cv_t<_Tp>; };
220
221 template<typename _Tp>
222 concept __has_member_value_type
223 = requires { typename _Tp::value_type; };
224
225 template<typename _Tp>
226 concept __has_member_element_type
227 = requires { typename _Tp::element_type; };
228
229 } // namespace __detail
230
231 template<typename> struct indirectly_readable_traits { };
232
233 template<typename _Tp>
234 struct indirectly_readable_traits<_Tp*>
235 : __detail::__cond_value_type<_Tp>
236 { };
237
238 template<typename _Iter> requires is_array_v<_Iter>
239 struct indirectly_readable_traits<_Iter>
240 { using value_type = remove_cv_t<remove_extent_t<_Iter>>; };
241
242 template<typename _Iter>
243 struct indirectly_readable_traits<const _Iter>
244 : indirectly_readable_traits<_Iter>
245 { };
246
247 template<__detail::__has_member_value_type _Tp>
248 struct indirectly_readable_traits<_Tp>
249 : __detail::__cond_value_type<typename _Tp::value_type>
250 { };
251
252 template<__detail::__has_member_element_type _Tp>
253 struct indirectly_readable_traits<_Tp>
254 : __detail::__cond_value_type<typename _Tp::element_type>
255 { };
256
257 // _GLIBCXX_RESOLVE_LIB_DEFECTS
258 // 3446. indirectly_readable_traits ambiguity for types with both [...]
259 template<__detail::__has_member_value_type _Tp>
260 requires __detail::__has_member_element_type<_Tp>
261 && same_as<remove_cv_t<typename _Tp::element_type>,
262 remove_cv_t<typename _Tp::value_type>>
263 struct indirectly_readable_traits<_Tp>
264 : __detail::__cond_value_type<typename _Tp::value_type>
265 { };
266
267 // LWG 3446 doesn't add this, but it's needed for the case where
268 // value_type and element_type are both present, but not the same type.
269 template<__detail::__has_member_value_type _Tp>
270 requires __detail::__has_member_element_type<_Tp>
271 struct indirectly_readable_traits<_Tp>
272 { };
273
274 namespace __detail
275 {
276 template<typename _Tp>
277 using __iter_value_t = typename
278 __iter_traits<_Tp, indirectly_readable_traits<_Tp>>::value_type;
279 } // namespace __detail
280
281 template<typename _Tp>
282 using iter_value_t = __detail::__iter_value_t<remove_cvref_t<_Tp>>;
283
284 namespace __detail
285 {
286 // _GLIBCXX_RESOLVE_LIB_DEFECTS
287 // 3420. cpp17-iterator should check [type] looks like an iterator first
288 template<typename _Iter>
289 concept __cpp17_iterator = requires(_Iter __it)
290 {
291 { *__it } -> __can_reference;
292 { ++__it } -> same_as<_Iter&>;
293 { *__it++ } -> __can_reference;
294 } && copyable<_Iter>;
295
296 template<typename _Iter>
297 concept __cpp17_input_iterator = __cpp17_iterator<_Iter>
298 && equality_comparable<_Iter>
299 && requires(_Iter __it)
300 {
301 typename incrementable_traits<_Iter>::difference_type;
302 typename indirectly_readable_traits<_Iter>::value_type;
303 typename common_reference_t<iter_reference_t<_Iter>&&,
304 typename indirectly_readable_traits<_Iter>::value_type&>;
305 typename common_reference_t<decltype(*__it++)&&,
306 typename indirectly_readable_traits<_Iter>::value_type&>;
307 requires signed_integral<
308 typename incrementable_traits<_Iter>::difference_type>;
309 };
310
311 template<typename _Iter>
312 concept __cpp17_fwd_iterator = __cpp17_input_iterator<_Iter>
313 && constructible_from<_Iter>
314 && is_lvalue_reference_v<iter_reference_t<_Iter>>
315 && same_as<remove_cvref_t<iter_reference_t<_Iter>>,
316 typename indirectly_readable_traits<_Iter>::value_type>
317 && requires(_Iter __it)
318 {
319 { __it++ } -> convertible_to<const _Iter&>;
320 { *__it++ } -> same_as<iter_reference_t<_Iter>>;
321 };
322
323 template<typename _Iter>
324 concept __cpp17_bidi_iterator = __cpp17_fwd_iterator<_Iter>
325 && requires(_Iter __it)
326 {
327 { --__it } -> same_as<_Iter&>;
328 { __it-- } -> convertible_to<const _Iter&>;
329 { *__it-- } -> same_as<iter_reference_t<_Iter>>;
330 };
331
332 template<typename _Iter>
333 concept __cpp17_randacc_iterator = __cpp17_bidi_iterator<_Iter>
334 && totally_ordered<_Iter>
335 && requires(_Iter __it,
336 typename incrementable_traits<_Iter>::difference_type __n)
337 {
338 { __it += __n } -> same_as<_Iter&>;
339 { __it -= __n } -> same_as<_Iter&>;
340 { __it + __n } -> same_as<_Iter>;
341 { __n + __it } -> same_as<_Iter>;
342 { __it - __n } -> same_as<_Iter>;
343 { __it - __it } -> same_as<decltype(__n)>;
344 { __it[__n] } -> convertible_to<iter_reference_t<_Iter>>;
345 };
346
347 template<typename _Iter>
348 concept __iter_with_nested_types = requires {
349 typename _Iter::iterator_category;
350 typename _Iter::value_type;
351 typename _Iter::difference_type;
352 typename _Iter::reference;
353 };
354
355 template<typename _Iter>
356 concept __iter_without_nested_types = !__iter_with_nested_types<_Iter>;
357
358 template<typename _Iter>
359 concept __iter_without_category
360 = !requires { typename _Iter::iterator_category; };
361
362 } // namespace __detail
363
364 template<typename _Iterator>
365 requires __detail::__iter_with_nested_types<_Iterator>
366 struct __iterator_traits<_Iterator, void>
367 {
368 private:
369 template<typename _Iter>
370 struct __ptr
371 { using type = void; };
372
373 template<typename _Iter> requires requires { typename _Iter::pointer; }
374 struct __ptr<_Iter>
375 { using type = typename _Iter::pointer; };
376
377 public:
378 using iterator_category = typename _Iterator::iterator_category;
379 using value_type = typename _Iterator::value_type;
380 using difference_type = typename _Iterator::difference_type;
381 using pointer = typename __ptr<_Iterator>::type;
382 using reference = typename _Iterator::reference;
383 };
384
385 template<typename _Iterator>
386 requires __detail::__iter_without_nested_types<_Iterator>
387 && __detail::__cpp17_input_iterator<_Iterator>
388 struct __iterator_traits<_Iterator, void>
389 {
390 private:
391 template<typename _Iter>
392 struct __cat
393 { using type = input_iterator_tag; };
394
395 template<typename _Iter>
396 requires requires { typename _Iter::iterator_category; }
397 struct __cat<_Iter>
398 { using type = typename _Iter::iterator_category; };
399
400 template<typename _Iter>
401 requires __detail::__iter_without_category<_Iter>
402 && __detail::__cpp17_randacc_iterator<_Iter>
403 struct __cat<_Iter>
404 { using type = random_access_iterator_tag; };
405
406 template<typename _Iter>
407 requires __detail::__iter_without_category<_Iter>
408 && __detail::__cpp17_bidi_iterator<_Iter>
409 struct __cat<_Iter>
410 { using type = bidirectional_iterator_tag; };
411
412 template<typename _Iter>
413 requires __detail::__iter_without_category<_Iter>
414 && __detail::__cpp17_fwd_iterator<_Iter>
415 struct __cat<_Iter>
416 { using type = forward_iterator_tag; };
417
418 template<typename _Iter>
419 struct __ptr
420 { using type = void; };
421
422 template<typename _Iter> requires requires { typename _Iter::pointer; }
423 struct __ptr<_Iter>
424 { using type = typename _Iter::pointer; };
425
426 template<typename _Iter>
427 requires (!requires { typename _Iter::pointer; }
428 && requires(_Iter& __it) { __it.operator->(); })
429 struct __ptr<_Iter>
430 { using type = decltype(std::declval<_Iter&>().operator->()); };
431
432 template<typename _Iter>
433 struct __ref
434 { using type = iter_reference_t<_Iter>; };
435
436 template<typename _Iter> requires requires { typename _Iter::reference; }
437 struct __ref<_Iter>
438 { using type = typename _Iter::reference; };
439
440 public:
441 using iterator_category = typename __cat<_Iterator>::type;
442 using value_type
443 = typename indirectly_readable_traits<_Iterator>::value_type;
444 using difference_type
445 = typename incrementable_traits<_Iterator>::difference_type;
446 using pointer = typename __ptr<_Iterator>::type;
447 using reference = typename __ref<_Iterator>::type;
448 };
449
450 template<typename _Iterator>
451 requires __detail::__iter_without_nested_types<_Iterator>
452 && __detail::__cpp17_iterator<_Iterator>
453 struct __iterator_traits<_Iterator, void>
454 {
455 private:
456 template<typename _Iter>
457 struct __diff
458 { using type = void; };
459
460 template<typename _Iter>
461 requires requires
462 { typename incrementable_traits<_Iter>::difference_type; }
463 struct __diff<_Iter>
464 {
465 using type = typename incrementable_traits<_Iter>::difference_type;
466 };
467
468 public:
469 using iterator_category = output_iterator_tag;
470 using value_type = void;
471 using difference_type = typename __diff<_Iterator>::type;
472 using pointer = void;
473 using reference = void;
474 };
475
476 namespace __detail
477 {
478 template<typename _Iter>
479 struct __iter_concept_impl;
480
481 // ITER_CONCEPT(I) is ITER_TRAITS(I)::iterator_concept if that is valid.
482 template<typename _Iter>
483 requires requires { typename __iter_traits<_Iter>::iterator_concept; }
484 struct __iter_concept_impl<_Iter>
485 { using type = typename __iter_traits<_Iter>::iterator_concept; };
486
487 // Otherwise, ITER_TRAITS(I)::iterator_category if that is valid.
488 template<typename _Iter>
489 requires (!requires { typename __iter_traits<_Iter>::iterator_concept; }
490 && requires { typename __iter_traits<_Iter>::iterator_category; })
491 struct __iter_concept_impl<_Iter>
492 { using type = typename __iter_traits<_Iter>::iterator_category; };
493
494 // Otherwise, random_access_tag if iterator_traits<I> is not specialized.
495 template<typename _Iter>
496 requires (!requires { typename __iter_traits<_Iter>::iterator_concept; }
497 && !requires { typename __iter_traits<_Iter>::iterator_category; }
498 && __primary_traits_iter<_Iter>)
499 struct __iter_concept_impl<_Iter>
500 { using type = random_access_iterator_tag; };
501
502 // Otherwise, there is no ITER_CONCEPT(I) type.
503 template<typename _Iter>
504 struct __iter_concept_impl
505 { };
506
507 // ITER_CONCEPT
508 template<typename _Iter>
509 using __iter_concept = typename __iter_concept_impl<_Iter>::type;
510
511 template<typename _In>
512 concept __indirectly_readable_impl = requires
513 {
514 typename iter_value_t<_In>;
515 typename iter_reference_t<_In>;
516 typename iter_rvalue_reference_t<_In>;
517 requires same_as<iter_reference_t<const _In>,
518 iter_reference_t<_In>>;
519 requires same_as<iter_rvalue_reference_t<const _In>,
520 iter_rvalue_reference_t<_In>>;
521 }
522 && common_reference_with<iter_reference_t<_In>&&, iter_value_t<_In>&>
523 && common_reference_with<iter_reference_t<_In>&&,
524 iter_rvalue_reference_t<_In>&&>
525 && common_reference_with<iter_rvalue_reference_t<_In>&&,
526 const iter_value_t<_In>&>;
527
528 } // namespace __detail
529
530 /// Requirements for types that are readable by applying operator*.
531 template<typename _In>
532 concept indirectly_readable
533 = __detail::__indirectly_readable_impl<remove_cvref_t<_In>>;
534
535 template<indirectly_readable _Tp>
536 using iter_common_reference_t
537 = common_reference_t<iter_reference_t<_Tp>, iter_value_t<_Tp>&>;
538
539 /// Requirements for writing a value into an iterator's referenced object.
540 template<typename _Out, typename _Tp>
541 concept indirectly_writable = requires(_Out&& __o, _Tp&& __t)
542 {
543 *__o = std::forward<_Tp>(__t);
544 *std::forward<_Out>(__o) = std::forward<_Tp>(__t);
545 const_cast<const iter_reference_t<_Out>&&>(*__o)
546 = std::forward<_Tp>(__t);
547 const_cast<const iter_reference_t<_Out>&&>(*std::forward<_Out>(__o))
548 = std::forward<_Tp>(__t);
549 };
550
551 namespace ranges::__detail
552 {
553 class __max_diff_type;
554 class __max_size_type;
555
556 template<typename _Tp>
557 concept __is_signed_int128
558 #if __SIZEOF_INT128__
559 = same_as<_Tp, __int128>;
560 #else
561 = false;
562 #endif
563
564 template<typename _Tp>
565 concept __is_unsigned_int128
566 #if __SIZEOF_INT128__
567 = same_as<_Tp, unsigned __int128>;
568 #else
569 = false;
570 #endif
571
572 template<typename _Tp>
573 concept __cv_bool = same_as<const volatile _Tp, const volatile bool>;
574
575 template<typename _Tp>
576 concept __integral_nonbool = integral<_Tp> && !__cv_bool<_Tp>;
577
578 template<typename _Tp>
579 concept __is_int128 = __is_signed_int128<_Tp> || __is_unsigned_int128<_Tp>;
580
581 template<typename _Tp>
582 concept __is_integer_like = __integral_nonbool<_Tp>
583 || __is_int128<_Tp>
584 || same_as<_Tp, __max_diff_type> || same_as<_Tp, __max_size_type>;
585
586 template<typename _Tp>
587 concept __is_signed_integer_like = signed_integral<_Tp>
588 || __is_signed_int128<_Tp>
589 || same_as<_Tp, __max_diff_type>;
590
591 } // namespace ranges::__detail
592
593 namespace __detail { using ranges::__detail::__is_signed_integer_like; }
594
595 /// Requirements on types that can be incremented with ++.
596 template<typename _Iter>
597 concept weakly_incrementable = default_initializable<_Iter>
598 && movable<_Iter>
599 && requires(_Iter __i)
600 {
601 typename iter_difference_t<_Iter>;
602 requires __detail::__is_signed_integer_like<iter_difference_t<_Iter>>;
603 { ++__i } -> same_as<_Iter&>;
604 __i++;
605 };
606
607 template<typename _Iter>
608 concept incrementable = regular<_Iter> && weakly_incrementable<_Iter>
609 && requires(_Iter __i) { { __i++ } -> same_as<_Iter>; };
610
611 template<typename _Iter>
612 concept input_or_output_iterator
613 = requires(_Iter __i) { { *__i } -> __detail::__can_reference; }
614 && weakly_incrementable<_Iter>;
615
616 template<typename _Sent, typename _Iter>
617 concept sentinel_for = semiregular<_Sent>
618 && input_or_output_iterator<_Iter>
619 && __detail::__weakly_eq_cmp_with<_Sent, _Iter>;
620
621 template<typename _Sent, typename _Iter>
622 inline constexpr bool disable_sized_sentinel_for = false;
623
624 template<typename _Sent, typename _Iter>
625 concept sized_sentinel_for = sentinel_for<_Sent, _Iter>
626 && !disable_sized_sentinel_for<remove_cv_t<_Sent>, remove_cv_t<_Iter>>
627 && requires(const _Iter& __i, const _Sent& __s)
628 {
629 { __s - __i } -> same_as<iter_difference_t<_Iter>>;
630 { __i - __s } -> same_as<iter_difference_t<_Iter>>;
631 };
632
633 template<typename _Iter>
634 concept input_iterator = input_or_output_iterator<_Iter>
635 && indirectly_readable<_Iter>
636 && requires { typename __detail::__iter_concept<_Iter>; }
637 && derived_from<__detail::__iter_concept<_Iter>, input_iterator_tag>;
638
639 template<typename _Iter, typename _Tp>
640 concept output_iterator = input_or_output_iterator<_Iter>
641 && indirectly_writable<_Iter, _Tp>
642 && requires(_Iter __i, _Tp&& __t) { *__i++ = std::forward<_Tp>(__t); };
643
644 template<typename _Iter>
645 concept forward_iterator = input_iterator<_Iter>
646 && derived_from<__detail::__iter_concept<_Iter>, forward_iterator_tag>
647 && incrementable<_Iter> && sentinel_for<_Iter, _Iter>;
648
649 template<typename _Iter>
650 concept bidirectional_iterator = forward_iterator<_Iter>
651 && derived_from<__detail::__iter_concept<_Iter>,
652 bidirectional_iterator_tag>
653 && requires(_Iter __i)
654 {
655 { --__i } -> same_as<_Iter&>;
656 { __i-- } -> same_as<_Iter>;
657 };
658
659 template<typename _Iter>
660 concept random_access_iterator = bidirectional_iterator<_Iter>
661 && derived_from<__detail::__iter_concept<_Iter>,
662 random_access_iterator_tag>
663 && totally_ordered<_Iter> && sized_sentinel_for<_Iter, _Iter>
664 && requires(_Iter __i, const _Iter __j,
665 const iter_difference_t<_Iter> __n)
666 {
667 { __i += __n } -> same_as<_Iter&>;
668 { __j + __n } -> same_as<_Iter>;
669 { __n + __j } -> same_as<_Iter>;
670 { __i -= __n } -> same_as<_Iter&>;
671 { __j - __n } -> same_as<_Iter>;
672 { __j[__n] } -> same_as<iter_reference_t<_Iter>>;
673 };
674
675 template<typename _Iter>
676 concept contiguous_iterator = random_access_iterator<_Iter>
677 && derived_from<__detail::__iter_concept<_Iter>, contiguous_iterator_tag>
678 && is_lvalue_reference_v<iter_reference_t<_Iter>>
679 && same_as<iter_value_t<_Iter>, remove_cvref_t<iter_reference_t<_Iter>>>
680 && requires(const _Iter& __i)
681 {
682 { std::to_address(__i) }
683 -> same_as<add_pointer_t<iter_reference_t<_Iter>>>;
684 };
685
686 // [indirectcallable], indirect callable requirements
687
688 // [indirectcallable.indirectinvocable], indirect callables
689
690 template<typename _Fn, typename _Iter>
691 concept indirectly_unary_invocable = indirectly_readable<_Iter>
692 && copy_constructible<_Fn> && invocable<_Fn&, iter_value_t<_Iter>&>
693 && invocable<_Fn&, iter_reference_t<_Iter>>
694 && invocable<_Fn&, iter_common_reference_t<_Iter>>
695 && common_reference_with<invoke_result_t<_Fn&, iter_value_t<_Iter>&>,
696 invoke_result_t<_Fn&, iter_reference_t<_Iter>>>;
697
698 template<typename _Fn, typename _Iter>
699 concept indirectly_regular_unary_invocable = indirectly_readable<_Iter>
700 && copy_constructible<_Fn>
701 && regular_invocable<_Fn&, iter_value_t<_Iter>&>
702 && regular_invocable<_Fn&, iter_reference_t<_Iter>>
703 && regular_invocable<_Fn&, iter_common_reference_t<_Iter>>
704 && common_reference_with<invoke_result_t<_Fn&, iter_value_t<_Iter>&>,
705 invoke_result_t<_Fn&, iter_reference_t<_Iter>>>;
706
707 template<typename _Fn, typename _Iter>
708 concept indirect_unary_predicate = indirectly_readable<_Iter>
709 && copy_constructible<_Fn> && predicate<_Fn&, iter_value_t<_Iter>&>
710 && predicate<_Fn&, iter_reference_t<_Iter>>
711 && predicate<_Fn&, iter_common_reference_t<_Iter>>;
712
713 template<typename _Fn, typename _I1, typename _I2>
714 concept indirect_binary_predicate
715 = indirectly_readable<_I1> && indirectly_readable<_I2>
716 && copy_constructible<_Fn>
717 && predicate<_Fn&, iter_value_t<_I1>&, iter_value_t<_I2>&>
718 && predicate<_Fn&, iter_value_t<_I1>&, iter_reference_t<_I2>>
719 && predicate<_Fn&, iter_reference_t<_I1>, iter_value_t<_I2>&>
720 && predicate<_Fn&, iter_reference_t<_I1>, iter_reference_t<_I2>>
721 && predicate<_Fn&, iter_common_reference_t<_I1>,
722 iter_common_reference_t<_I2>>;
723
724 template<typename _Fn, typename _I1, typename _I2 = _I1>
725 concept indirect_equivalence_relation
726 = indirectly_readable<_I1> && indirectly_readable<_I2>
727 && copy_constructible<_Fn>
728 && equivalence_relation<_Fn&, iter_value_t<_I1>&, iter_value_t<_I2>&>
729 && equivalence_relation<_Fn&, iter_value_t<_I1>&, iter_reference_t<_I2>>
730 && equivalence_relation<_Fn&, iter_reference_t<_I1>, iter_value_t<_I2>&>
731 && equivalence_relation<_Fn&, iter_reference_t<_I1>,
732 iter_reference_t<_I2>>
733 && equivalence_relation<_Fn&, iter_common_reference_t<_I1>,
734 iter_common_reference_t<_I2>>;
735
736 template<typename _Fn, typename _I1, typename _I2 = _I1>
737 concept indirect_strict_weak_order
738 = indirectly_readable<_I1> && indirectly_readable<_I2>
739 && copy_constructible<_Fn>
740 && strict_weak_order<_Fn&, iter_value_t<_I1>&, iter_value_t<_I2>&>
741 && strict_weak_order<_Fn&, iter_value_t<_I1>&, iter_reference_t<_I2>>
742 && strict_weak_order<_Fn&, iter_reference_t<_I1>, iter_value_t<_I2>&>
743 && strict_weak_order<_Fn&, iter_reference_t<_I1>, iter_reference_t<_I2>>
744 && strict_weak_order<_Fn&, iter_common_reference_t<_I1>,
745 iter_common_reference_t<_I2>>;
746
747 template<typename _Fn, typename... _Is>
748 requires (indirectly_readable<_Is> && ...)
749 && invocable<_Fn, iter_reference_t<_Is>...>
750 using indirect_result_t = invoke_result_t<_Fn, iter_reference_t<_Is>...>;
751
752 /// [projected], projected
753 template<indirectly_readable _Iter,
754 indirectly_regular_unary_invocable<_Iter> _Proj>
755 struct projected
756 {
757 using value_type = remove_cvref_t<indirect_result_t<_Proj&, _Iter>>;
758
759 indirect_result_t<_Proj&, _Iter> operator*() const; // not defined
760 };
761
762 template<weakly_incrementable _Iter, typename _Proj>
763 struct incrementable_traits<projected<_Iter, _Proj>>
764 { using difference_type = iter_difference_t<_Iter>; };
765
766 // [alg.req], common algorithm requirements
767
768 /// [alg.req.ind.move], concept `indirectly_movable`
769
770 template<typename _In, typename _Out>
771 concept indirectly_movable = indirectly_readable<_In>
772 && indirectly_writable<_Out, iter_rvalue_reference_t<_In>>;
773
774 template<typename _In, typename _Out>
775 concept indirectly_movable_storable = indirectly_movable<_In, _Out>
776 && indirectly_writable<_Out, iter_value_t<_In>>
777 && movable<iter_value_t<_In>>
778 && constructible_from<iter_value_t<_In>, iter_rvalue_reference_t<_In>>
779 && assignable_from<iter_value_t<_In>&, iter_rvalue_reference_t<_In>>;
780
781 /// [alg.req.ind.copy], concept `indirectly_copyable`
782 template<typename _In, typename _Out>
783 concept indirectly_copyable = indirectly_readable<_In>
784 && indirectly_writable<_Out, iter_reference_t<_In>>;
785
786 template<typename _In, typename _Out>
787 concept indirectly_copyable_storable = indirectly_copyable<_In, _Out>
788 && indirectly_writable<_Out, iter_value_t<_In>&>
789 && indirectly_writable<_Out, const iter_value_t<_In>&>
790 && indirectly_writable<_Out, iter_value_t<_In>&&>
791 && indirectly_writable<_Out, const iter_value_t<_In>&&>
792 && copyable<iter_value_t<_In>>
793 && constructible_from<iter_value_t<_In>, iter_reference_t<_In>>
794 && assignable_from<iter_value_t<_In>&, iter_reference_t<_In>>;
795
796 namespace ranges
797 {
798 namespace __cust_iswap
799 {
800 template<typename _It1, typename _It2>
801 void iter_swap(_It1, _It2) = delete;
802
803 template<typename _Tp, typename _Up>
804 concept __adl_iswap
805 = (std::__detail::__class_or_enum<remove_reference_t<_Tp>>
806 || std::__detail::__class_or_enum<remove_reference_t<_Up>>)
807 && requires(_Tp&& __t, _Up&& __u) {
808 iter_swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
809 };
810
811 template<typename _Xp, typename _Yp>
812 constexpr iter_value_t<_Xp>
813 __iter_exchange_move(_Xp&& __x, _Yp&& __y)
814 noexcept(noexcept(iter_value_t<_Xp>(iter_move(__x)))
815 && noexcept(*__x = iter_move(__y)))
816 {
817 iter_value_t<_Xp> __old_value(iter_move(__x));
818 *__x = iter_move(__y);
819 return __old_value;
820 }
821
822 struct _IterSwap
823 {
824 private:
825 template<typename _Tp, typename _Up>
826 static constexpr bool
827 _S_noexcept()
828 {
829 if constexpr (__adl_iswap<_Tp, _Up>)
830 return noexcept(iter_swap(std::declval<_Tp>(),
831 std::declval<_Up>()));
832 else if constexpr (indirectly_readable<_Tp>
833 && indirectly_readable<_Up>
834 && swappable_with<iter_reference_t<_Tp>, iter_reference_t<_Up>>)
835 return noexcept(ranges::swap(*std::declval<_Tp>(),
836 *std::declval<_Up>()));
837 else
838 return noexcept(*std::declval<_Tp>()
839 = __iter_exchange_move(std::declval<_Up>(),
840 std::declval<_Tp>()));
841 }
842
843 public:
844 template<typename _Tp, typename _Up>
845 requires __adl_iswap<_Tp, _Up>
846 || (indirectly_readable<remove_reference_t<_Tp>>
847 && indirectly_readable<remove_reference_t<_Up>>
848 && swappable_with<iter_reference_t<_Tp>, iter_reference_t<_Up>>)
849 || (indirectly_movable_storable<_Tp, _Up>
850 && indirectly_movable_storable<_Up, _Tp>)
851 constexpr void
852 operator()(_Tp&& __e1, _Up&& __e2) const
853 noexcept(_S_noexcept<_Tp, _Up>())
854 {
855 if constexpr (__adl_iswap<_Tp, _Up>)
856 iter_swap(static_cast<_Tp&&>(__e1), static_cast<_Up&&>(__e2));
857 else if constexpr (indirectly_readable<_Tp>
858 && indirectly_readable<_Up>
859 && swappable_with<iter_reference_t<_Tp>, iter_reference_t<_Up>>)
860 ranges::swap(*__e1, *__e2);
861 else
862 *__e1 = __iter_exchange_move(__e2, __e1);
863 }
864 };
865 } // namespace __cust_iswap
866
867 inline namespace __cust
868 {
869 inline constexpr __cust_iswap::_IterSwap iter_swap{};
870 } // inline namespace __cust
871
872 } // namespace ranges
873
874 /// [alg.req.ind.swap], concept `indirectly_swappable`
875 template<typename _I1, typename _I2 = _I1>
876 concept indirectly_swappable
877 = indirectly_readable<_I1> && indirectly_readable<_I2>
878 && requires(const _I1 __i1, const _I2 __i2)
879 {
880 ranges::iter_swap(__i1, __i1);
881 ranges::iter_swap(__i2, __i2);
882 ranges::iter_swap(__i1, __i2);
883 ranges::iter_swap(__i2, __i1);
884 };
885
886 /// [alg.req.ind.cmp], concept `indirectly_comparable`
887 template<typename _I1, typename _I2, typename _Rel, typename _P1 = identity,
888 typename _P2 = identity>
889 concept indirectly_comparable
890 = indirect_binary_predicate<_Rel, projected<_I1, _P1>,
891 projected<_I2, _P2>>;
892
893 /// [alg.req.permutable], concept `permutable`
894 template<typename _Iter>
895 concept permutable = forward_iterator<_Iter>
896 && indirectly_movable_storable<_Iter, _Iter>
897 && indirectly_swappable<_Iter, _Iter>;
898
899 /// [alg.req.mergeable], concept `mergeable`
900 template<typename _I1, typename _I2, typename _Out,
901 typename _Rel = ranges::less, typename _P1 = identity,
902 typename _P2 = identity>
903 concept mergeable = input_iterator<_I1> && input_iterator<_I2>
904 && weakly_incrementable<_Out> && indirectly_copyable<_I1, _Out>
905 && indirectly_copyable<_I2, _Out>
906 && indirect_strict_weak_order<_Rel, projected<_I1, _P1>,
907 projected<_I2, _P2>>;
908
909 /// [alg.req.sortable], concept `sortable`
910 template<typename _Iter, typename _Rel = ranges::less,
911 typename _Proj = identity>
912 concept sortable = permutable<_Iter>
913 && indirect_strict_weak_order<_Rel, projected<_Iter, _Proj>>;
914
915 struct unreachable_sentinel_t
916 {
917 template<weakly_incrementable _It>
918 friend constexpr bool
919 operator==(unreachable_sentinel_t, const _It&) noexcept
920 { return false; }
921 };
922
923 inline constexpr unreachable_sentinel_t unreachable_sentinel{};
924
925 struct default_sentinel_t { };
926 inline constexpr default_sentinel_t default_sentinel{};
927
928 // This is the namespace for [range.access] CPOs.
929 namespace ranges::__cust_access
930 {
931 using std::__detail::__class_or_enum;
932
933 struct _Decay_copy final
934 {
935 template<typename _Tp>
936 constexpr decay_t<_Tp>
937 operator()(_Tp&& __t) const
938 noexcept(is_nothrow_convertible_v<_Tp, decay_t<_Tp>>)
939 { return std::forward<_Tp>(__t); }
940 } inline constexpr __decay_copy{};
941
942 template<typename _Tp>
943 concept __member_begin = requires(_Tp& __t)
944 {
945 { __decay_copy(__t.begin()) } -> input_or_output_iterator;
946 };
947
948 // Poison pills so that unqualified lookup doesn't find std::begin.
949 void begin(auto&) = delete;
950 void begin(const auto&) = delete;
951
952 template<typename _Tp>
953 concept __adl_begin = __class_or_enum<remove_reference_t<_Tp>>
954 && requires(_Tp& __t)
955 {
956 { __decay_copy(begin(__t)) } -> input_or_output_iterator;
957 };
958
959 // Simplified version of std::ranges::begin that only supports lvalues,
960 // for use by __range_iter_t below.
961 template<typename _Tp>
962 requires is_array_v<_Tp> || __member_begin<_Tp&> || __adl_begin<_Tp&>
963 auto
964 __begin(_Tp& __t)
965 {
966 if constexpr (is_array_v<_Tp>)
967 return __t + 0;
968 else if constexpr (__member_begin<_Tp&>)
969 return __t.begin();
970 else
971 return begin(__t);
972 }
973 } // namespace ranges::__cust_access
974
975 namespace __detail
976 {
977 // Implementation of std::ranges::iterator_t, without using ranges::begin.
978 template<typename _Tp>
979 using __range_iter_t
980 = decltype(ranges::__cust_access::__begin(std::declval<_Tp&>()));
981
982 } // namespace __detail
983
984 _GLIBCXX_END_NAMESPACE_VERSION
985 } // namespace std
986 #endif // C++20 library concepts
987 #endif // _ITERATOR_CONCEPTS_H
988