libstdc++
ranges
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1// <ranges> -*- 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 include/ranges
26 * This is a Standard C++ Library header.
27 * @ingroup concepts
28 */
29
30#ifndef _GLIBCXX_RANGES
31#define _GLIBCXX_RANGES 1
32
33#if __cplusplus > 201703L
34
35#pragma GCC system_header
36
37#include <concepts>
38
39#if __cpp_lib_concepts
40
41#include <compare>
42#include <initializer_list>
43#include <iterator>
44#include <optional>
45#include <tuple>
46#include <bits/ranges_util.h>
47#include <bits/refwrap.h>
48
49/**
50 * @defgroup ranges Ranges
51 *
52 * Components for dealing with ranges of elements.
53 */
54
55namespace std _GLIBCXX_VISIBILITY(default)
56{
57_GLIBCXX_BEGIN_NAMESPACE_VERSION
58namespace ranges
59{
60 // [range.access] customization point objects
61 // [range.req] range and view concepts
62 // [range.dangling] dangling iterator handling
63 // Defined in <bits/ranges_base.h>
64
65 // [view.interface] View interface
66 // [range.subrange] Sub-ranges
67 // Defined in <bits/ranges_util.h>
68
69 // C++20 24.6 [range.factories] Range factories
70
71 /// A view that contains no elements.
72 template<typename _Tp> requires is_object_v<_Tp>
73 class empty_view
74 : public view_interface<empty_view<_Tp>>
75 {
76 public:
77 static constexpr _Tp* begin() noexcept { return nullptr; }
78 static constexpr _Tp* end() noexcept { return nullptr; }
79 static constexpr _Tp* data() noexcept { return nullptr; }
80 static constexpr size_t size() noexcept { return 0; }
81 static constexpr bool empty() noexcept { return true; }
82 };
83
84 template<typename _Tp>
85 inline constexpr bool enable_borrowed_range<empty_view<_Tp>> = true;
86
87 namespace __detail
88 {
89 template<typename _Tp>
90 concept __boxable = copy_constructible<_Tp> && is_object_v<_Tp>;
91
92 template<__boxable _Tp>
93 struct __box : std::optional<_Tp>
94 {
95 using std::optional<_Tp>::optional;
96
97 constexpr
98 __box()
99 noexcept(is_nothrow_default_constructible_v<_Tp>)
100 requires default_initializable<_Tp>
101 : std::optional<_Tp>{std::in_place}
102 { }
103
104 __box(const __box&) = default;
105 __box(__box&&) = default;
106
107 using std::optional<_Tp>::operator=;
108
109 // _GLIBCXX_RESOLVE_LIB_DEFECTS
110 // 3477. Simplify constraints for semiregular-box
111 __box&
112 operator=(const __box& __that)
113 noexcept(is_nothrow_copy_constructible_v<_Tp>)
114 requires (!copyable<_Tp>)
115 {
116 if (this != std::__addressof(__that))
117 {
118 if ((bool)__that)
119 this->emplace(*__that);
120 else
121 this->reset();
122 }
123 return *this;
124 }
125
126 __box&
127 operator=(__box&& __that)
128 noexcept(is_nothrow_move_constructible_v<_Tp>)
129 requires (!movable<_Tp>)
130 {
131 if (this != std::__addressof(__that))
132 {
133 if ((bool)__that)
134 this->emplace(std::move(*__that));
135 else
136 this->reset();
137 }
138 return *this;
139 }
140 };
141
142 // For types which are already copyable, this specialization of the
143 // copyable wrapper stores the object directly without going through
144 // std::optional. It provides just the subset of the primary template's
145 // API that we currently use.
146 template<__boxable _Tp>
147 requires copyable<_Tp>
148 struct __box<_Tp>
149 {
150 private:
151 [[no_unique_address]] _Tp _M_value = _Tp();
152
153 public:
154 __box() requires default_initializable<_Tp> = default;
155
156 constexpr explicit
157 __box(const _Tp& __t)
158 noexcept(is_nothrow_copy_constructible_v<_Tp>)
159 : _M_value(__t)
160 { }
161
162 constexpr explicit
163 __box(_Tp&& __t)
164 noexcept(is_nothrow_move_constructible_v<_Tp>)
165 : _M_value(std::move(__t))
166 { }
167
168 template<typename... _Args>
169 requires constructible_from<_Tp, _Args...>
170 constexpr explicit
171 __box(in_place_t, _Args&&... __args)
172 noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
173 : _M_value(std::forward<_Args>(__args)...)
174 { }
175
176 constexpr bool
177 has_value() const noexcept
178 { return true; };
179
180 constexpr _Tp&
181 operator*() noexcept
182 { return _M_value; }
183
184 constexpr const _Tp&
185 operator*() const noexcept
186 { return _M_value; }
187
188 constexpr _Tp*
189 operator->() noexcept
190 { return std::__addressof(_M_value); }
191
192 constexpr const _Tp*
193 operator->() const noexcept
194 { return std::__addressof(_M_value); }
195 };
196 } // namespace __detail
197
198 /// A view that contains exactly one element.
199 template<copy_constructible _Tp> requires is_object_v<_Tp>
200 class single_view : public view_interface<single_view<_Tp>>
201 {
202 public:
203 single_view() requires default_initializable<_Tp> = default;
204
205 constexpr explicit
206 single_view(const _Tp& __t)
207 : _M_value(__t)
208 { }
209
210 constexpr explicit
211 single_view(_Tp&& __t)
212 : _M_value(std::move(__t))
213 { }
214
215 // _GLIBCXX_RESOLVE_LIB_DEFECTS
216 // 3428. single_view's in place constructor should be explicit
217 template<typename... _Args>
218 requires constructible_from<_Tp, _Args...>
219 constexpr explicit
220 single_view(in_place_t, _Args&&... __args)
221 : _M_value{in_place, std::forward<_Args>(__args)...}
222 { }
223
224 constexpr _Tp*
225 begin() noexcept
226 { return data(); }
227
228 constexpr const _Tp*
229 begin() const noexcept
230 { return data(); }
231
232 constexpr _Tp*
233 end() noexcept
234 { return data() + 1; }
235
236 constexpr const _Tp*
237 end() const noexcept
238 { return data() + 1; }
239
240 static constexpr size_t
241 size() noexcept
242 { return 1; }
243
244 constexpr _Tp*
245 data() noexcept
246 { return _M_value.operator->(); }
247
248 constexpr const _Tp*
249 data() const noexcept
250 { return _M_value.operator->(); }
251
252 private:
253 [[no_unique_address]] __detail::__box<_Tp> _M_value;
254 };
255
256 template<typename _Tp>
257 single_view(_Tp) -> single_view<_Tp>;
258
259 namespace __detail
260 {
261 template<typename _Wp>
262 constexpr auto __to_signed_like(_Wp __w) noexcept
263 {
264 if constexpr (!integral<_Wp>)
265 return iter_difference_t<_Wp>();
266 else if constexpr (sizeof(iter_difference_t<_Wp>) > sizeof(_Wp))
267 return iter_difference_t<_Wp>(__w);
268 else if constexpr (sizeof(ptrdiff_t) > sizeof(_Wp))
269 return ptrdiff_t(__w);
270 else if constexpr (sizeof(long long) > sizeof(_Wp))
271 return (long long)(__w);
272#ifdef __SIZEOF_INT128__
273 else if constexpr (__SIZEOF_INT128__ > sizeof(_Wp))
274 return __int128(__w);
275#endif
276 else
277 return __max_diff_type(__w);
278 }
279
280 template<typename _Wp>
281 using __iota_diff_t = decltype(__to_signed_like(std::declval<_Wp>()));
282
283 template<typename _It>
284 concept __decrementable = incrementable<_It>
285 && requires(_It __i)
286 {
287 { --__i } -> same_as<_It&>;
288 { __i-- } -> same_as<_It>;
289 };
290
291 template<typename _It>
292 concept __advanceable = __decrementable<_It> && totally_ordered<_It>
293 && requires( _It __i, const _It __j, const __iota_diff_t<_It> __n)
294 {
295 { __i += __n } -> same_as<_It&>;
296 { __i -= __n } -> same_as<_It&>;
297 _It(__j + __n);
298 _It(__n + __j);
299 _It(__j - __n);
300 { __j - __j } -> convertible_to<__iota_diff_t<_It>>;
301 };
302
303 template<typename _Winc>
304 struct __iota_view_iter_cat
305 { };
306
307 template<incrementable _Winc>
308 struct __iota_view_iter_cat<_Winc>
309 { using iterator_category = input_iterator_tag; };
310 } // namespace __detail
311
312 template<weakly_incrementable _Winc,
313 semiregular _Bound = unreachable_sentinel_t>
314 requires std::__detail::__weakly_eq_cmp_with<_Winc, _Bound>
315 && copyable<_Winc>
316 class iota_view : public view_interface<iota_view<_Winc, _Bound>>
317 {
318 private:
319 struct _Sentinel;
320
321 struct _Iterator : __detail::__iota_view_iter_cat<_Winc>
322 {
323 private:
324 static auto
325 _S_iter_concept()
326 {
327 using namespace __detail;
328 if constexpr (__advanceable<_Winc>)
329 return random_access_iterator_tag{};
330 else if constexpr (__decrementable<_Winc>)
331 return bidirectional_iterator_tag{};
332 else if constexpr (incrementable<_Winc>)
333 return forward_iterator_tag{};
334 else
335 return input_iterator_tag{};
336 }
337
338 public:
339 using iterator_concept = decltype(_S_iter_concept());
340 // iterator_category defined in __iota_view_iter_cat
341 using value_type = _Winc;
342 using difference_type = __detail::__iota_diff_t<_Winc>;
343
344 _Iterator() requires default_initializable<_Winc> = default;
345
346 constexpr explicit
347 _Iterator(_Winc __value)
348 : _M_value(__value) { }
349
350 constexpr _Winc
351 operator*() const noexcept(is_nothrow_copy_constructible_v<_Winc>)
352 { return _M_value; }
353
354 constexpr _Iterator&
355 operator++()
356 {
357 ++_M_value;
358 return *this;
359 }
360
361 constexpr void
362 operator++(int)
363 { ++*this; }
364
365 constexpr _Iterator
366 operator++(int) requires incrementable<_Winc>
367 {
368 auto __tmp = *this;
369 ++*this;
370 return __tmp;
371 }
372
373 constexpr _Iterator&
374 operator--() requires __detail::__decrementable<_Winc>
375 {
376 --_M_value;
377 return *this;
378 }
379
380 constexpr _Iterator
381 operator--(int) requires __detail::__decrementable<_Winc>
382 {
383 auto __tmp = *this;
384 --*this;
385 return __tmp;
386 }
387
388 constexpr _Iterator&
389 operator+=(difference_type __n) requires __detail::__advanceable<_Winc>
390 {
391 using __detail::__is_integer_like;
392 using __detail::__is_signed_integer_like;
393 if constexpr (__is_integer_like<_Winc>
394 && !__is_signed_integer_like<_Winc>)
395 {
396 if (__n >= difference_type(0))
397 _M_value += static_cast<_Winc>(__n);
398 else
399 _M_value -= static_cast<_Winc>(-__n);
400 }
401 else
402 _M_value += __n;
403 return *this;
404 }
405
406 constexpr _Iterator&
407 operator-=(difference_type __n) requires __detail::__advanceable<_Winc>
408 {
409 using __detail::__is_integer_like;
410 using __detail::__is_signed_integer_like;
411 if constexpr (__is_integer_like<_Winc>
412 && !__is_signed_integer_like<_Winc>)
413 {
414 if (__n >= difference_type(0))
415 _M_value -= static_cast<_Winc>(__n);
416 else
417 _M_value += static_cast<_Winc>(-__n);
418 }
419 else
420 _M_value -= __n;
421 return *this;
422 }
423
424 constexpr _Winc
425 operator[](difference_type __n) const
426 requires __detail::__advanceable<_Winc>
427 { return _Winc(_M_value + __n); }
428
429 friend constexpr bool
430 operator==(const _Iterator& __x, const _Iterator& __y)
431 requires equality_comparable<_Winc>
432 { return __x._M_value == __y._M_value; }
433
434 friend constexpr bool
435 operator<(const _Iterator& __x, const _Iterator& __y)
436 requires totally_ordered<_Winc>
437 { return __x._M_value < __y._M_value; }
438
439 friend constexpr bool
440 operator>(const _Iterator& __x, const _Iterator& __y)
441 requires totally_ordered<_Winc>
442 { return __y < __x; }
443
444 friend constexpr bool
445 operator<=(const _Iterator& __x, const _Iterator& __y)
446 requires totally_ordered<_Winc>
447 { return !(__y < __x); }
448
449 friend constexpr bool
450 operator>=(const _Iterator& __x, const _Iterator& __y)
451 requires totally_ordered<_Winc>
452 { return !(__x < __y); }
453
454#ifdef __cpp_lib_three_way_comparison
455 friend constexpr auto
456 operator<=>(const _Iterator& __x, const _Iterator& __y)
457 requires totally_ordered<_Winc> && three_way_comparable<_Winc>
458 { return __x._M_value <=> __y._M_value; }
459#endif
460
461 friend constexpr _Iterator
462 operator+(_Iterator __i, difference_type __n)
463 requires __detail::__advanceable<_Winc>
464 {
465 __i += __n;
466 return __i;
467 }
468
469 friend constexpr _Iterator
470 operator+(difference_type __n, _Iterator __i)
471 requires __detail::__advanceable<_Winc>
472 { return __i += __n; }
473
474 friend constexpr _Iterator
475 operator-(_Iterator __i, difference_type __n)
476 requires __detail::__advanceable<_Winc>
477 {
478 __i -= __n;
479 return __i;
480 }
481
482 friend constexpr difference_type
483 operator-(const _Iterator& __x, const _Iterator& __y)
484 requires __detail::__advanceable<_Winc>
485 {
486 using __detail::__is_integer_like;
487 using __detail::__is_signed_integer_like;
488 using _Dt = difference_type;
489 if constexpr (__is_integer_like<_Winc>)
490 {
491 if constexpr (__is_signed_integer_like<_Winc>)
492 return _Dt(_Dt(__x._M_value) - _Dt(__y._M_value));
493 else
494 return (__y._M_value > __x._M_value)
495 ? _Dt(-_Dt(__y._M_value - __x._M_value))
496 : _Dt(__x._M_value - __y._M_value);
497 }
498 else
499 return __x._M_value - __y._M_value;
500 }
501
502 private:
503 _Winc _M_value = _Winc();
504
505 friend iota_view;
506 friend _Sentinel;
507 };
508
509 struct _Sentinel
510 {
511 private:
512 constexpr bool
513 _M_equal(const _Iterator& __x) const
514 { return __x._M_value == _M_bound; }
515
516 constexpr auto
517 _M_distance_from(const _Iterator& __x) const
518 { return _M_bound - __x._M_value; }
519
520 _Bound _M_bound = _Bound();
521
522 public:
523 _Sentinel() = default;
524
525 constexpr explicit
526 _Sentinel(_Bound __bound)
527 : _M_bound(__bound) { }
528
529 friend constexpr bool
530 operator==(const _Iterator& __x, const _Sentinel& __y)
531 { return __y._M_equal(__x); }
532
533 friend constexpr iter_difference_t<_Winc>
534 operator-(const _Iterator& __x, const _Sentinel& __y)
535 requires sized_sentinel_for<_Bound, _Winc>
536 { return -__y._M_distance_from(__x); }
537
538 friend constexpr iter_difference_t<_Winc>
539 operator-(const _Sentinel& __x, const _Iterator& __y)
540 requires sized_sentinel_for<_Bound, _Winc>
541 { return __x._M_distance_from(__y); }
542
543 friend iota_view;
544 };
545
546 _Winc _M_value = _Winc();
547 [[no_unique_address]] _Bound _M_bound = _Bound();
548
549 public:
550 iota_view() requires default_initializable<_Winc> = default;
551
552 constexpr explicit
553 iota_view(_Winc __value)
554 : _M_value(__value)
555 { }
556
557 constexpr
558 iota_view(type_identity_t<_Winc> __value,
559 type_identity_t<_Bound> __bound)
560 : _M_value(__value), _M_bound(__bound)
561 {
562 if constexpr (totally_ordered_with<_Winc, _Bound>)
563 __glibcxx_assert( bool(__value <= __bound) );
564 }
565
566 constexpr
567 iota_view(_Iterator __first, _Iterator __last)
568 requires same_as<_Winc, _Bound>
569 : iota_view(__first._M_value, __last._M_value)
570 { }
571
572 constexpr
573 iota_view(_Iterator __first, unreachable_sentinel_t __last)
574 requires same_as<_Bound, unreachable_sentinel_t>
575 : iota_view(__first._M_value, __last)
576 { }
577
578 constexpr
579 iota_view(_Iterator __first, _Sentinel __last)
580 requires (!same_as<_Winc, _Bound>) && (!same_as<_Bound, unreachable_sentinel_t>)
581 : iota_view(__first._M_value, __last._M_bound)
582 { }
583
584 constexpr _Iterator
585 begin() const { return _Iterator{_M_value}; }
586
587 constexpr auto
588 end() const
589 {
590 if constexpr (same_as<_Bound, unreachable_sentinel_t>)
591 return unreachable_sentinel;
592 else
593 return _Sentinel{_M_bound};
594 }
595
596 constexpr _Iterator
597 end() const requires same_as<_Winc, _Bound>
598 { return _Iterator{_M_bound}; }
599
600 constexpr auto
601 size() const
602 requires (same_as<_Winc, _Bound> && __detail::__advanceable<_Winc>)
603 || (integral<_Winc> && integral<_Bound>)
604 || sized_sentinel_for<_Bound, _Winc>
605 {
606 using __detail::__is_integer_like;
607 using __detail::__to_unsigned_like;
608 if constexpr (integral<_Winc> && integral<_Bound>)
609 {
610 using _Up = make_unsigned_t<decltype(_M_bound - _M_value)>;
611 return _Up(_M_bound) - _Up(_M_value);
612 }
613 else if constexpr (__is_integer_like<_Winc>)
614 return __to_unsigned_like(_M_bound) - __to_unsigned_like(_M_value);
615 else
616 return __to_unsigned_like(_M_bound - _M_value);
617 }
618 };
619
620 template<typename _Winc, typename _Bound>
621 requires (!__detail::__is_integer_like<_Winc>
622 || !__detail::__is_integer_like<_Bound>
623 || (__detail::__is_signed_integer_like<_Winc>
624 == __detail::__is_signed_integer_like<_Bound>))
625 iota_view(_Winc, _Bound) -> iota_view<_Winc, _Bound>;
626
627 template<weakly_incrementable _Winc, semiregular _Bound>
628 inline constexpr bool
629 enable_borrowed_range<iota_view<_Winc, _Bound>> = true;
630
631namespace views
632{
633 template<typename _Tp>
634 inline constexpr empty_view<_Tp> empty{};
635
636 struct _Single
637 {
638 template<typename _Tp>
639 constexpr auto
640 operator()(_Tp&& __e) const
641 { return single_view<decay_t<_Tp>>(std::forward<_Tp>(__e)); }
642 };
643
644 inline constexpr _Single single{};
645
646 struct _Iota
647 {
648 template<typename _Tp>
649 constexpr auto
650 operator()(_Tp&& __e) const
651 { return iota_view(std::forward<_Tp>(__e)); }
652
653 template<typename _Tp, typename _Up>
654 constexpr auto
655 operator()(_Tp&& __e, _Up&& __f) const
656 { return iota_view(std::forward<_Tp>(__e), std::forward<_Up>(__f)); }
657 };
658
659 inline constexpr _Iota iota{};
660} // namespace views
661
662 namespace __detail
663 {
664 template<typename _Val, typename _CharT, typename _Traits>
665 concept __stream_extractable
666 = requires(basic_istream<_CharT, _Traits>& is, _Val& t) { is >> t; };
667 } // namespace __detail
668
669 template<movable _Val, typename _CharT,
670 typename _Traits = char_traits<_CharT>>
671 requires default_initializable<_Val>
672 && __detail::__stream_extractable<_Val, _CharT, _Traits>
673 class basic_istream_view
674 : public view_interface<basic_istream_view<_Val, _CharT, _Traits>>
675 {
676 public:
677 basic_istream_view() = default;
678
679 constexpr explicit
680 basic_istream_view(basic_istream<_CharT, _Traits>& __stream)
681 : _M_stream(std::__addressof(__stream))
682 { }
683
684 constexpr auto
685 begin()
686 {
687 if (_M_stream != nullptr)
688 *_M_stream >> _M_object;
689 return _Iterator{this};
690 }
691
692 constexpr default_sentinel_t
693 end() const noexcept
694 { return default_sentinel; }
695
696 private:
697 basic_istream<_CharT, _Traits>* _M_stream = nullptr;
698 _Val _M_object = _Val();
699
700 struct _Iterator
701 {
702 public:
703 using iterator_concept = input_iterator_tag;
704 using difference_type = ptrdiff_t;
705 using value_type = _Val;
706
707 _Iterator() = default;
708
709 constexpr explicit
710 _Iterator(basic_istream_view* __parent) noexcept
711 : _M_parent(__parent)
712 { }
713
714 _Iterator(const _Iterator&) = delete;
715 _Iterator(_Iterator&&) = default;
716 _Iterator& operator=(const _Iterator&) = delete;
717 _Iterator& operator=(_Iterator&&) = default;
718
719 _Iterator&
720 operator++()
721 {
722 __glibcxx_assert(_M_parent->_M_stream != nullptr);
723 *_M_parent->_M_stream >> _M_parent->_M_object;
724 return *this;
725 }
726
727 void
728 operator++(int)
729 { ++*this; }
730
731 _Val&
732 operator*() const
733 {
734 __glibcxx_assert(_M_parent->_M_stream != nullptr);
735 return _M_parent->_M_object;
736 }
737
738 friend bool
739 operator==(const _Iterator& __x, default_sentinel_t)
740 { return __x._M_at_end(); }
741
742 private:
743 basic_istream_view* _M_parent = nullptr;
744
745 bool
746 _M_at_end() const
747 { return _M_parent == nullptr || !*_M_parent->_M_stream; }
748 };
749
750 friend _Iterator;
751 };
752
753 template<typename _Val, typename _CharT, typename _Traits>
754 basic_istream_view<_Val, _CharT, _Traits>
755 istream_view(basic_istream<_CharT, _Traits>& __s)
756 { return basic_istream_view<_Val, _CharT, _Traits>{__s}; }
757
758 // C++20 24.7 [range.adaptors] Range adaptors
759
760namespace __detail
761{
762 struct _Empty { };
763
764 // Alias for a type that is conditionally present
765 // (and is an empty type otherwise).
766 // Data members using this alias should use [[no_unique_address]] so that
767 // they take no space when not needed.
768 template<bool _Present, typename _Tp>
769 using __maybe_present_t = conditional_t<_Present, _Tp, _Empty>;
770
771 // Alias for a type that is conditionally const.
772 template<bool _Const, typename _Tp>
773 using __maybe_const_t = conditional_t<_Const, const _Tp, _Tp>;
774
775} // namespace __detail
776
777namespace views::__adaptor
778{
779 // True if the range adaptor _Adaptor can be applied with _Args.
780 template<typename _Adaptor, typename... _Args>
781 concept __adaptor_invocable
782 = requires { std::declval<_Adaptor>()(declval<_Args>()...); };
783
784 // True if the range adaptor non-closure _Adaptor can be partially applied
785 // with _Args.
786 template<typename _Adaptor, typename... _Args>
787 concept __adaptor_partial_app_viable = (_Adaptor::_S_arity > 1)
788 && (sizeof...(_Args) == _Adaptor::_S_arity - 1)
789 && (constructible_from<decay_t<_Args>, _Args> && ...);
790
791 template<typename _Adaptor, typename... _Args>
792 struct _Partial;
793
794 template<typename _Lhs, typename _Rhs>
795 struct _Pipe;
796
797 // The base class of every range adaptor closure.
798 //
799 // The derived class should define the optional static data member
800 // _S_has_simple_call_op to true if the behavior of this adaptor is
801 // independent of the constness/value category of the adaptor object.
802 struct _RangeAdaptorClosure
803 {
804 // range | adaptor is equivalent to adaptor(range).
805 template<typename _Self, typename _Range>
806 requires derived_from<remove_cvref_t<_Self>, _RangeAdaptorClosure>
807 && __adaptor_invocable<_Self, _Range>
808 friend constexpr auto
809 operator|(_Range&& __r, _Self&& __self)
810 { return std::forward<_Self>(__self)(std::forward<_Range>(__r)); }
811
812 // Compose the adaptors __lhs and __rhs into a pipeline, returning
813 // another range adaptor closure object.
814 template<typename _Lhs, typename _Rhs>
815 requires derived_from<_Lhs, _RangeAdaptorClosure>
816 && derived_from<_Rhs, _RangeAdaptorClosure>
817 friend constexpr auto
818 operator|(_Lhs __lhs, _Rhs __rhs)
819 { return _Pipe<_Lhs, _Rhs>{std::move(__lhs), std::move(__rhs)}; }
820 };
821
822 // The base class of every range adaptor non-closure.
823 //
824 // The static data member _Derived::_S_arity must contain the total number of
825 // arguments that the adaptor takes, and the class _Derived must introduce
826 // _RangeAdaptor::operator() into the class scope via a using-declaration.
827 //
828 // The optional static data member _Derived::_S_has_simple_extra_args should
829 // be defined to true if the behavior of this adaptor is independent of the
830 // constness/value category of the extra arguments. This data member could
831 // also be defined as a variable template parameterized by the types of the
832 // extra arguments.
833 template<typename _Derived>
834 struct _RangeAdaptor
835 {
836 // Partially apply the arguments __args to the range adaptor _Derived,
837 // returning a range adaptor closure object.
838 template<typename... _Args>
839 requires __adaptor_partial_app_viable<_Derived, _Args...>
840 constexpr auto
841 operator()(_Args&&... __args) const
842 {
843 return _Partial<_Derived, decay_t<_Args>...>{std::forward<_Args>(__args)...};
844 }
845 };
846
847 // True if the range adaptor closure _Adaptor has a simple operator(), i.e.
848 // one that's not overloaded according to constness or value category of the
849 // _Adaptor object.
850 template<typename _Adaptor>
851 concept __closure_has_simple_call_op = _Adaptor::_S_has_simple_call_op;
852
853 // True if the behavior of the range adaptor non-closure _Adaptor is
854 // independent of the value category of its extra arguments _Args.
855 template<typename _Adaptor, typename... _Args>
856 concept __adaptor_has_simple_extra_args = _Adaptor::_S_has_simple_extra_args
857 || _Adaptor::template _S_has_simple_extra_args<_Args...>;
858
859 // A range adaptor closure that represents partial application of
860 // the range adaptor _Adaptor with arguments _Args.
861 template<typename _Adaptor, typename... _Args>
862 struct _Partial : _RangeAdaptorClosure
863 {
864 tuple<_Args...> _M_args;
865
866 constexpr
867 _Partial(_Args... __args)
868 : _M_args(std::move(__args)...)
869 { }
870
871 // Invoke _Adaptor with arguments __r, _M_args... according to the
872 // value category of this _Partial object.
873 template<typename _Range>
874 requires __adaptor_invocable<_Adaptor, _Range, const _Args&...>
875 constexpr auto
876 operator()(_Range&& __r) const &
877 {
878 auto __forwarder = [&__r] (const auto&... __args) {
879 return _Adaptor{}(std::forward<_Range>(__r), __args...);
880 };
881 return std::apply(__forwarder, _M_args);
882 }
883
884 template<typename _Range>
885 requires __adaptor_invocable<_Adaptor, _Range, _Args...>
886 constexpr auto
887 operator()(_Range&& __r) &&
888 {
889 auto __forwarder = [&__r] (auto&... __args) {
890 return _Adaptor{}(std::forward<_Range>(__r), std::move(__args)...);
891 };
892 return std::apply(__forwarder, _M_args);
893 }
894
895 template<typename _Range>
896 constexpr auto
897 operator()(_Range&& __r) const && = delete;
898 };
899
900 // A lightweight specialization of the above primary template for
901 // the common case where _Adaptor accepts a single extra argument.
902 template<typename _Adaptor, typename _Arg>
903 struct _Partial<_Adaptor, _Arg> : _RangeAdaptorClosure
904 {
905 _Arg _M_arg;
906
907 constexpr
908 _Partial(_Arg __arg)
909 : _M_arg(std::move(__arg))
910 { }
911
912 template<typename _Range>
913 requires __adaptor_invocable<_Adaptor, _Range, const _Arg&>
914 constexpr auto
915 operator()(_Range&& __r) const &
916 { return _Adaptor{}(std::forward<_Range>(__r), _M_arg); }
917
918 template<typename _Range>
919 requires __adaptor_invocable<_Adaptor, _Range, _Arg>
920 constexpr auto
921 operator()(_Range&& __r) &&
922 { return _Adaptor{}(std::forward<_Range>(__r), std::move(_M_arg)); }
923
924 template<typename _Range>
925 constexpr auto
926 operator()(_Range&& __r) const && = delete;
927 };
928
929 // Partial specialization of the primary template for the case where the extra
930 // arguments of the adaptor can always be safely and efficiently forwarded by
931 // const reference. This lets us get away with a single operator() overload,
932 // which makes overload resolution failure diagnostics more concise.
933 template<typename _Adaptor, typename... _Args>
934 requires __adaptor_has_simple_extra_args<_Adaptor, _Args...>
935 && (is_trivially_copyable_v<_Args> && ...)
936 struct _Partial<_Adaptor, _Args...> : _RangeAdaptorClosure
937 {
938 tuple<_Args...> _M_args;
939
940 constexpr
941 _Partial(_Args... __args)
942 : _M_args(std::move(__args)...)
943 { }
944
945 // Invoke _Adaptor with arguments __r, const _M_args&... regardless
946 // of the value category of this _Partial object.
947 template<typename _Range>
948 requires __adaptor_invocable<_Adaptor, _Range, const _Args&...>
949 constexpr auto
950 operator()(_Range&& __r) const
951 {
952 auto __forwarder = [&__r] (const auto&... __args) {
953 return _Adaptor{}(std::forward<_Range>(__r), __args...);
954 };
955 return std::apply(__forwarder, _M_args);
956 }
957
958 static constexpr bool _S_has_simple_call_op = true;
959 };
960
961 // A lightweight specialization of the above template for the common case
962 // where _Adaptor accepts a single extra argument.
963 template<typename _Adaptor, typename _Arg>
964 requires __adaptor_has_simple_extra_args<_Adaptor, _Arg>
965 && is_trivially_copyable_v<_Arg>
966 struct _Partial<_Adaptor, _Arg> : _RangeAdaptorClosure
967 {
968 _Arg _M_arg;
969
970 constexpr
971 _Partial(_Arg __arg)
972 : _M_arg(std::move(__arg))
973 { }
974
975 template<typename _Range>
976 requires __adaptor_invocable<_Adaptor, _Range, const _Arg&>
977 constexpr auto
978 operator()(_Range&& __r) const
979 { return _Adaptor{}(std::forward<_Range>(__r), _M_arg); }
980
981 static constexpr bool _S_has_simple_call_op = true;
982 };
983
984 template<typename _Lhs, typename _Rhs, typename _Range>
985 concept __pipe_invocable
986 = requires { std::declval<_Rhs>()(std::declval<_Lhs>()(std::declval<_Range>())); };
987
988 // A range adaptor closure that represents composition of the range
989 // adaptor closures _Lhs and _Rhs.
990 template<typename _Lhs, typename _Rhs>
991 struct _Pipe : _RangeAdaptorClosure
992 {
993 [[no_unique_address]] _Lhs _M_lhs;
994 [[no_unique_address]] _Rhs _M_rhs;
995
996 constexpr
997 _Pipe(_Lhs __lhs, _Rhs __rhs)
998 : _M_lhs(std::move(__lhs)), _M_rhs(std::move(__rhs))
999 { }
1000
1001 // Invoke _M_rhs(_M_lhs(__r)) according to the value category of this
1002 // range adaptor closure object.
1003 template<typename _Range>
1004 requires __pipe_invocable<const _Lhs&, const _Rhs&, _Range>
1005 constexpr auto
1006 operator()(_Range&& __r) const &
1007 { return _M_rhs(_M_lhs(std::forward<_Range>(__r))); }
1008
1009 template<typename _Range>
1010 requires __pipe_invocable<_Lhs, _Rhs, _Range>
1011 constexpr auto
1012 operator()(_Range&& __r) &&
1013 { return std::move(_M_rhs)(std::move(_M_lhs)(std::forward<_Range>(__r))); }
1014
1015 template<typename _Range>
1016 constexpr auto
1017 operator()(_Range&& __r) const && = delete;
1018 };
1019
1020 // A partial specialization of the above primary template for the case where
1021 // both adaptor operands have a simple operator(). This in turn lets us
1022 // implement composition using a single simple operator(), which makes
1023 // overload resolution failure diagnostics more concise.
1024 template<typename _Lhs, typename _Rhs>
1025 requires __closure_has_simple_call_op<_Lhs>
1026 && __closure_has_simple_call_op<_Rhs>
1027 struct _Pipe<_Lhs, _Rhs> : _RangeAdaptorClosure
1028 {
1029 [[no_unique_address]] _Lhs _M_lhs;
1030 [[no_unique_address]] _Rhs _M_rhs;
1031
1032 constexpr
1033 _Pipe(_Lhs __lhs, _Rhs __rhs)
1034 : _M_lhs(std::move(__lhs)), _M_rhs(std::move(__rhs))
1035 { }
1036
1037 template<typename _Range>
1038 requires __pipe_invocable<const _Lhs&, const _Rhs&, _Range>
1039 constexpr auto
1040 operator()(_Range&& __r) const
1041 { return _M_rhs(_M_lhs(std::forward<_Range>(__r))); }
1042
1043 static constexpr bool _S_has_simple_call_op = true;
1044 };
1045} // namespace views::__adaptor
1046
1047 template<range _Range> requires is_object_v<_Range>
1048 class ref_view : public view_interface<ref_view<_Range>>
1049 {
1050 private:
1051 _Range* _M_r = nullptr;
1052
1053 static void _S_fun(_Range&); // not defined
1054 static void _S_fun(_Range&&) = delete;
1055
1056 public:
1057 constexpr
1058 ref_view() noexcept = default;
1059
1060 template<__detail::__not_same_as<ref_view> _Tp>
1061 requires convertible_to<_Tp, _Range&>
1062 && requires { _S_fun(declval<_Tp>()); }
1063 constexpr
1064 ref_view(_Tp&& __t)
1065 : _M_r(std::__addressof(static_cast<_Range&>(std::forward<_Tp>(__t))))
1066 { }
1067
1068 constexpr _Range&
1069 base() const
1070 { return *_M_r; }
1071
1072 constexpr iterator_t<_Range>
1073 begin() const
1074 { return ranges::begin(*_M_r); }
1075
1076 constexpr sentinel_t<_Range>
1077 end() const
1078 { return ranges::end(*_M_r); }
1079
1080 constexpr bool
1081 empty() const requires requires { ranges::empty(*_M_r); }
1082 { return ranges::empty(*_M_r); }
1083
1084 constexpr auto
1085 size() const requires sized_range<_Range>
1086 { return ranges::size(*_M_r); }
1087
1088 constexpr auto
1089 data() const requires contiguous_range<_Range>
1090 { return ranges::data(*_M_r); }
1091 };
1092
1093 template<typename _Range>
1094 ref_view(_Range&) -> ref_view<_Range>;
1095
1096 template<typename _Tp>
1097 inline constexpr bool enable_borrowed_range<ref_view<_Tp>> = true;
1098
1099 namespace views
1100 {
1101 namespace __detail
1102 {
1103 template<typename _Range>
1104 concept __can_ref_view = requires { ref_view{std::declval<_Range>()}; };
1105
1106 template<typename _Range>
1107 concept __can_subrange = requires { subrange{std::declval<_Range>()}; };
1108 } // namespace __detail
1109
1110 struct _All : __adaptor::_RangeAdaptorClosure
1111 {
1112 template<viewable_range _Range>
1113 requires view<decay_t<_Range>>
1114 || __detail::__can_ref_view<_Range>
1115 || __detail::__can_subrange<_Range>
1116 constexpr auto
1117 operator()(_Range&& __r) const
1118 {
1119 if constexpr (view<decay_t<_Range>>)
1120 return std::forward<_Range>(__r);
1121 else if constexpr (__detail::__can_ref_view<_Range>)
1122 return ref_view{std::forward<_Range>(__r)};
1123 else
1124 return subrange{std::forward<_Range>(__r)};
1125 }
1126
1127 static constexpr bool _S_has_simple_call_op = true;
1128 };
1129
1130 inline constexpr _All all;
1131
1132 template<viewable_range _Range>
1133 using all_t = decltype(all(std::declval<_Range>()));
1134 } // namespace views
1135
1136 namespace __detail
1137 {
1138 template<typename _Tp>
1139 struct __non_propagating_cache
1140 {
1141 // When _Tp is not an object type (e.g. is a reference type), we make
1142 // __non_propagating_cache<_Tp> empty rather than ill-formed so that
1143 // users can easily conditionally declare data members with this type
1144 // (such as join_view::_M_inner).
1145 };
1146
1147 template<typename _Tp>
1148 requires is_object_v<_Tp>
1149 struct __non_propagating_cache<_Tp> : protected _Optional_base<_Tp>
1150 {
1151 __non_propagating_cache() = default;
1152
1153 constexpr
1154 __non_propagating_cache(const __non_propagating_cache&) noexcept
1155 { }
1156
1157 constexpr
1158 __non_propagating_cache(__non_propagating_cache&& __other) noexcept
1159 { __other._M_reset(); }
1160
1161 constexpr __non_propagating_cache&
1162 operator=(const __non_propagating_cache& __other) noexcept
1163 {
1164 if (std::__addressof(__other) != this)
1165 this->_M_reset();
1166 return *this;
1167 }
1168
1169 constexpr __non_propagating_cache&
1170 operator=(__non_propagating_cache&& __other) noexcept
1171 {
1172 this->_M_reset();
1173 __other._M_reset();
1174 return *this;
1175 }
1176
1177 constexpr _Tp&
1178 operator*() noexcept
1179 { return this->_M_get(); }
1180
1181 constexpr const _Tp&
1182 operator*() const noexcept
1183 { return this->_M_get(); }
1184
1185 template<typename _Iter>
1186 _Tp&
1187 _M_emplace_deref(const _Iter& __i)
1188 {
1189 this->_M_reset();
1190 // Using _Optional_base::_M_construct to initialize from '*__i'
1191 // would incur an extra move due to the indirection, so we instead
1192 // use placement new directly.
1193 ::new ((void *) std::__addressof(this->_M_payload._M_payload)) _Tp(*__i);
1194 this->_M_payload._M_engaged = true;
1195 return this->_M_get();
1196 }
1197 };
1198
1199 template<range _Range>
1200 struct _CachedPosition
1201 {
1202 constexpr bool
1203 _M_has_value() const
1204 { return false; }
1205
1206 constexpr iterator_t<_Range>
1207 _M_get(const _Range&) const
1208 {
1209 __glibcxx_assert(false);
1210 __builtin_unreachable();
1211 }
1212
1213 constexpr void
1214 _M_set(const _Range&, const iterator_t<_Range>&) const
1215 { }
1216 };
1217
1218 template<forward_range _Range>
1219 struct _CachedPosition<_Range>
1220 : protected __non_propagating_cache<iterator_t<_Range>>
1221 {
1222 constexpr bool
1223 _M_has_value() const
1224 { return this->_M_is_engaged(); }
1225
1226 constexpr iterator_t<_Range>
1227 _M_get(const _Range&) const
1228 {
1229 __glibcxx_assert(_M_has_value());
1230 return **this;
1231 }
1232
1233 constexpr void
1234 _M_set(const _Range&, const iterator_t<_Range>& __it)
1235 {
1236 __glibcxx_assert(!_M_has_value());
1237 std::construct_at(std::__addressof(this->_M_payload._M_payload),
1238 in_place, __it);
1239 this->_M_payload._M_engaged = true;
1240 }
1241 };
1242
1243 template<random_access_range _Range>
1244 requires (sizeof(range_difference_t<_Range>)
1245 <= sizeof(iterator_t<_Range>))
1246 struct _CachedPosition<_Range>
1247 {
1248 private:
1249 range_difference_t<_Range> _M_offset = -1;
1250
1251 public:
1252 _CachedPosition() = default;
1253
1254 constexpr
1255 _CachedPosition(const _CachedPosition&) = default;
1256
1257 constexpr
1258 _CachedPosition(_CachedPosition&& __other) noexcept
1259 { *this = std::move(__other); }
1260
1261 constexpr _CachedPosition&
1262 operator=(const _CachedPosition&) = default;
1263
1264 constexpr _CachedPosition&
1265 operator=(_CachedPosition&& __other) noexcept
1266 {
1267 // Propagate the cached offset, but invalidate the source.
1268 _M_offset = __other._M_offset;
1269 __other._M_offset = -1;
1270 return *this;
1271 }
1272
1273 constexpr bool
1274 _M_has_value() const
1275 { return _M_offset >= 0; }
1276
1277 constexpr iterator_t<_Range>
1278 _M_get(_Range& __r) const
1279 {
1280 __glibcxx_assert(_M_has_value());
1281 return ranges::begin(__r) + _M_offset;
1282 }
1283
1284 constexpr void
1285 _M_set(_Range& __r, const iterator_t<_Range>& __it)
1286 {
1287 __glibcxx_assert(!_M_has_value());
1288 _M_offset = __it - ranges::begin(__r);
1289 }
1290 };
1291 } // namespace __detail
1292
1293 namespace __detail
1294 {
1295 template<typename _Base>
1296 struct __filter_view_iter_cat
1297 { };
1298
1299 template<forward_range _Base>
1300 struct __filter_view_iter_cat<_Base>
1301 {
1302 private:
1303 static auto
1304 _S_iter_cat()
1305 {
1306 using _Cat = typename iterator_traits<iterator_t<_Base>>::iterator_category;
1307 if constexpr (derived_from<_Cat, bidirectional_iterator_tag>)
1308 return bidirectional_iterator_tag{};
1309 else if constexpr (derived_from<_Cat, forward_iterator_tag>)
1310 return forward_iterator_tag{};
1311 else
1312 return _Cat{};
1313 }
1314 public:
1315 using iterator_category = decltype(_S_iter_cat());
1316 };
1317 } // namespace __detail
1318
1319 template<input_range _Vp,
1320 indirect_unary_predicate<iterator_t<_Vp>> _Pred>
1321 requires view<_Vp> && is_object_v<_Pred>
1322 class filter_view : public view_interface<filter_view<_Vp, _Pred>>
1323 {
1324 private:
1325 struct _Sentinel;
1326
1327 struct _Iterator : __detail::__filter_view_iter_cat<_Vp>
1328 {
1329 private:
1330 static constexpr auto
1331 _S_iter_concept()
1332 {
1333 if constexpr (bidirectional_range<_Vp>)
1334 return bidirectional_iterator_tag{};
1335 else if constexpr (forward_range<_Vp>)
1336 return forward_iterator_tag{};
1337 else
1338 return input_iterator_tag{};
1339 }
1340
1341 friend filter_view;
1342
1343 using _Vp_iter = iterator_t<_Vp>;
1344
1345 _Vp_iter _M_current = _Vp_iter();
1346 filter_view* _M_parent = nullptr;
1347
1348 public:
1349 using iterator_concept = decltype(_S_iter_concept());
1350 // iterator_category defined in __filter_view_iter_cat
1351 using value_type = range_value_t<_Vp>;
1352 using difference_type = range_difference_t<_Vp>;
1353
1354 _Iterator() requires default_initializable<_Vp_iter> = default;
1355
1356 constexpr
1357 _Iterator(filter_view* __parent, _Vp_iter __current)
1358 : _M_current(std::move(__current)),
1359 _M_parent(__parent)
1360 { }
1361
1362 constexpr const _Vp_iter&
1363 base() const & noexcept
1364 { return _M_current; }
1365
1366 constexpr _Vp_iter
1367 base() &&
1368 { return std::move(_M_current); }
1369
1370 constexpr range_reference_t<_Vp>
1371 operator*() const
1372 { return *_M_current; }
1373
1374 constexpr _Vp_iter
1375 operator->() const
1376 requires __detail::__has_arrow<_Vp_iter>
1377 && copyable<_Vp_iter>
1378 { return _M_current; }
1379
1380 constexpr _Iterator&
1381 operator++()
1382 {
1383 _M_current = ranges::find_if(std::move(++_M_current),
1384 ranges::end(_M_parent->_M_base),
1385 std::ref(*_M_parent->_M_pred));
1386 return *this;
1387 }
1388
1389 constexpr void
1390 operator++(int)
1391 { ++*this; }
1392
1393 constexpr _Iterator
1394 operator++(int) requires forward_range<_Vp>
1395 {
1396 auto __tmp = *this;
1397 ++*this;
1398 return __tmp;
1399 }
1400
1401 constexpr _Iterator&
1402 operator--() requires bidirectional_range<_Vp>
1403 {
1404 do
1405 --_M_current;
1406 while (!std::__invoke(*_M_parent->_M_pred, *_M_current));
1407 return *this;
1408 }
1409
1410 constexpr _Iterator
1411 operator--(int) requires bidirectional_range<_Vp>
1412 {
1413 auto __tmp = *this;
1414 --*this;
1415 return __tmp;
1416 }
1417
1418 friend constexpr bool
1419 operator==(const _Iterator& __x, const _Iterator& __y)
1420 requires equality_comparable<_Vp_iter>
1421 { return __x._M_current == __y._M_current; }
1422
1423 friend constexpr range_rvalue_reference_t<_Vp>
1424 iter_move(const _Iterator& __i)
1425 noexcept(noexcept(ranges::iter_move(__i._M_current)))
1426 { return ranges::iter_move(__i._M_current); }
1427
1428 friend constexpr void
1429 iter_swap(const _Iterator& __x, const _Iterator& __y)
1430 noexcept(noexcept(ranges::iter_swap(__x._M_current, __y._M_current)))
1431 requires indirectly_swappable<_Vp_iter>
1432 { ranges::iter_swap(__x._M_current, __y._M_current); }
1433 };
1434
1435 struct _Sentinel
1436 {
1437 private:
1438 sentinel_t<_Vp> _M_end = sentinel_t<_Vp>();
1439
1440 constexpr bool
1441 __equal(const _Iterator& __i) const
1442 { return __i._M_current == _M_end; }
1443
1444 public:
1445 _Sentinel() = default;
1446
1447 constexpr explicit
1448 _Sentinel(filter_view* __parent)
1449 : _M_end(ranges::end(__parent->_M_base))
1450 { }
1451
1452 constexpr sentinel_t<_Vp>
1453 base() const
1454 { return _M_end; }
1455
1456 friend constexpr bool
1457 operator==(const _Iterator& __x, const _Sentinel& __y)
1458 { return __y.__equal(__x); }
1459 };
1460
1461 [[no_unique_address]] __detail::__box<_Pred> _M_pred;
1462 [[no_unique_address]] __detail::_CachedPosition<_Vp> _M_cached_begin;
1463 _Vp _M_base = _Vp();
1464
1465 public:
1466 filter_view() requires (default_initializable<_Vp>
1467 && default_initializable<_Pred>)
1468 = default;
1469
1470 constexpr
1471 filter_view(_Vp __base, _Pred __pred)
1472 : _M_pred(std::move(__pred)), _M_base(std::move(__base))
1473 { }
1474
1475 constexpr _Vp
1476 base() const& requires copy_constructible<_Vp>
1477 { return _M_base; }
1478
1479 constexpr _Vp
1480 base() &&
1481 { return std::move(_M_base); }
1482
1483 constexpr const _Pred&
1484 pred() const
1485 { return *_M_pred; }
1486
1487 constexpr _Iterator
1488 begin()
1489 {
1490 if (_M_cached_begin._M_has_value())
1491 return {this, _M_cached_begin._M_get(_M_base)};
1492
1493 __glibcxx_assert(_M_pred.has_value());
1494 auto __it = ranges::find_if(ranges::begin(_M_base),
1495 ranges::end(_M_base),
1496 std::ref(*_M_pred));
1497 _M_cached_begin._M_set(_M_base, __it);
1498 return {this, std::move(__it)};
1499 }
1500
1501 constexpr auto
1502 end()
1503 {
1504 if constexpr (common_range<_Vp>)
1505 return _Iterator{this, ranges::end(_M_base)};
1506 else
1507 return _Sentinel{this};
1508 }
1509 };
1510
1511 template<typename _Range, typename _Pred>
1512 filter_view(_Range&&, _Pred) -> filter_view<views::all_t<_Range>, _Pred>;
1513
1514 namespace views
1515 {
1516 namespace __detail
1517 {
1518 template<typename _Range, typename _Pred>
1519 concept __can_filter_view
1520 = requires { filter_view(std::declval<_Range>(), std::declval<_Pred>()); };
1521 } // namespace __detail
1522
1523 struct _Filter : __adaptor::_RangeAdaptor<_Filter>
1524 {
1525 template<viewable_range _Range, typename _Pred>
1526 requires __detail::__can_filter_view<_Range, _Pred>
1527 constexpr auto
1528 operator()(_Range&& __r, _Pred&& __p) const
1529 {
1530 return filter_view(std::forward<_Range>(__r), std::forward<_Pred>(__p));
1531 }
1532
1533 using _RangeAdaptor<_Filter>::operator();
1534 static constexpr int _S_arity = 2;
1535 static constexpr bool _S_has_simple_extra_args = true;
1536 };
1537
1538 inline constexpr _Filter filter;
1539 } // namespace views
1540
1541 template<input_range _Vp, copy_constructible _Fp>
1542 requires view<_Vp> && is_object_v<_Fp>
1543 && regular_invocable<_Fp&, range_reference_t<_Vp>>
1544 && std::__detail::__can_reference<invoke_result_t<_Fp&,
1545 range_reference_t<_Vp>>>
1546 class transform_view : public view_interface<transform_view<_Vp, _Fp>>
1547 {
1548 private:
1549 template<bool _Const>
1550 using _Base = __detail::__maybe_const_t<_Const, _Vp>;
1551
1552 template<bool _Const>
1553 struct __iter_cat
1554 { };
1555
1556 template<bool _Const>
1557 requires forward_range<_Base<_Const>>
1558 struct __iter_cat<_Const>
1559 {
1560 private:
1561 static auto
1562 _S_iter_cat()
1563 {
1564 using _Base = transform_view::_Base<_Const>;
1565 using _Res = invoke_result_t<_Fp&, range_reference_t<_Base>>;
1566 if constexpr (is_lvalue_reference_v<_Res>)
1567 {
1568 using _Cat
1569 = typename iterator_traits<iterator_t<_Base>>::iterator_category;
1570 if constexpr (derived_from<_Cat, contiguous_iterator_tag>)
1571 return random_access_iterator_tag{};
1572 else
1573 return _Cat{};
1574 }
1575 else
1576 return input_iterator_tag{};
1577 }
1578 public:
1579 using iterator_category = decltype(_S_iter_cat());
1580 };
1581
1582 template<bool _Const>
1583 struct _Sentinel;
1584
1585 template<bool _Const>
1586 struct _Iterator : __iter_cat<_Const>
1587 {
1588 private:
1589 using _Parent = __detail::__maybe_const_t<_Const, transform_view>;
1590 using _Base = transform_view::_Base<_Const>;
1591
1592 static auto
1593 _S_iter_concept()
1594 {
1595 if constexpr (random_access_range<_Base>)
1596 return random_access_iterator_tag{};
1597 else if constexpr (bidirectional_range<_Base>)
1598 return bidirectional_iterator_tag{};
1599 else if constexpr (forward_range<_Base>)
1600 return forward_iterator_tag{};
1601 else
1602 return input_iterator_tag{};
1603 }
1604
1605 using _Base_iter = iterator_t<_Base>;
1606
1607 _Base_iter _M_current = _Base_iter();
1608 _Parent* _M_parent = nullptr;
1609
1610 public:
1611 using iterator_concept = decltype(_S_iter_concept());
1612 // iterator_category defined in __transform_view_iter_cat
1613 using value_type
1614 = remove_cvref_t<invoke_result_t<_Fp&, range_reference_t<_Base>>>;
1615 using difference_type = range_difference_t<_Base>;
1616
1617 _Iterator() requires default_initializable<_Base_iter> = default;
1618
1619 constexpr
1620 _Iterator(_Parent* __parent, _Base_iter __current)
1621 : _M_current(std::move(__current)),
1622 _M_parent(__parent)
1623 { }
1624
1625 constexpr
1626 _Iterator(_Iterator<!_Const> __i)
1627 requires _Const
1628 && convertible_to<iterator_t<_Vp>, _Base_iter>
1629 : _M_current(std::move(__i._M_current)), _M_parent(__i._M_parent)
1630 { }
1631
1632 constexpr const _Base_iter&
1633 base() const & noexcept
1634 { return _M_current; }
1635
1636 constexpr _Base_iter
1637 base() &&
1638 { return std::move(_M_current); }
1639
1640 constexpr decltype(auto)
1641 operator*() const
1642 noexcept(noexcept(std::__invoke(*_M_parent->_M_fun, *_M_current)))
1643 { return std::__invoke(*_M_parent->_M_fun, *_M_current); }
1644
1645 constexpr _Iterator&
1646 operator++()
1647 {
1648 ++_M_current;
1649 return *this;
1650 }
1651
1652 constexpr void
1653 operator++(int)
1654 { ++_M_current; }
1655
1656 constexpr _Iterator
1657 operator++(int) requires forward_range<_Base>
1658 {
1659 auto __tmp = *this;
1660 ++*this;
1661 return __tmp;
1662 }
1663
1664 constexpr _Iterator&
1665 operator--() requires bidirectional_range<_Base>
1666 {
1667 --_M_current;
1668 return *this;
1669 }
1670
1671 constexpr _Iterator
1672 operator--(int) requires bidirectional_range<_Base>
1673 {
1674 auto __tmp = *this;
1675 --*this;
1676 return __tmp;
1677 }
1678
1679 constexpr _Iterator&
1680 operator+=(difference_type __n) requires random_access_range<_Base>
1681 {
1682 _M_current += __n;
1683 return *this;
1684 }
1685
1686 constexpr _Iterator&
1687 operator-=(difference_type __n) requires random_access_range<_Base>
1688 {
1689 _M_current -= __n;
1690 return *this;
1691 }
1692
1693 constexpr decltype(auto)
1694 operator[](difference_type __n) const
1695 requires random_access_range<_Base>
1696 { return std::__invoke(*_M_parent->_M_fun, _M_current[__n]); }
1697
1698 friend constexpr bool
1699 operator==(const _Iterator& __x, const _Iterator& __y)
1700 requires equality_comparable<_Base_iter>
1701 { return __x._M_current == __y._M_current; }
1702
1703 friend constexpr bool
1704 operator<(const _Iterator& __x, const _Iterator& __y)
1705 requires random_access_range<_Base>
1706 { return __x._M_current < __y._M_current; }
1707
1708 friend constexpr bool
1709 operator>(const _Iterator& __x, const _Iterator& __y)
1710 requires random_access_range<_Base>
1711 { return __y < __x; }
1712
1713 friend constexpr bool
1714 operator<=(const _Iterator& __x, const _Iterator& __y)
1715 requires random_access_range<_Base>
1716 { return !(__y < __x); }
1717
1718 friend constexpr bool
1719 operator>=(const _Iterator& __x, const _Iterator& __y)
1720 requires random_access_range<_Base>
1721 { return !(__x < __y); }
1722
1723#ifdef __cpp_lib_three_way_comparison
1724 friend constexpr auto
1725 operator<=>(const _Iterator& __x, const _Iterator& __y)
1726 requires random_access_range<_Base>
1727 && three_way_comparable<_Base_iter>
1728 { return __x._M_current <=> __y._M_current; }
1729#endif
1730
1731 friend constexpr _Iterator
1732 operator+(_Iterator __i, difference_type __n)
1733 requires random_access_range<_Base>
1734 { return {__i._M_parent, __i._M_current + __n}; }
1735
1736 friend constexpr _Iterator
1737 operator+(difference_type __n, _Iterator __i)
1738 requires random_access_range<_Base>
1739 { return {__i._M_parent, __i._M_current + __n}; }
1740
1741 friend constexpr _Iterator
1742 operator-(_Iterator __i, difference_type __n)
1743 requires random_access_range<_Base>
1744 { return {__i._M_parent, __i._M_current - __n}; }
1745
1746 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1747 // 3483. transform_view::iterator's difference is overconstrained
1748 friend constexpr difference_type
1749 operator-(const _Iterator& __x, const _Iterator& __y)
1750 requires sized_sentinel_for<iterator_t<_Base>, iterator_t<_Base>>
1751 { return __x._M_current - __y._M_current; }
1752
1753 friend constexpr decltype(auto)
1754 iter_move(const _Iterator& __i) noexcept(noexcept(*__i))
1755 {
1756 if constexpr (is_lvalue_reference_v<decltype(*__i)>)
1757 return std::move(*__i);
1758 else
1759 return *__i;
1760 }
1761
1762 friend _Iterator<!_Const>;
1763 template<bool> friend struct _Sentinel;
1764 };
1765
1766 template<bool _Const>
1767 struct _Sentinel
1768 {
1769 private:
1770 using _Parent = __detail::__maybe_const_t<_Const, transform_view>;
1771 using _Base = transform_view::_Base<_Const>;
1772
1773 template<bool _Const2>
1774 constexpr auto
1775 __distance_from(const _Iterator<_Const2>& __i) const
1776 { return _M_end - __i._M_current; }
1777
1778 template<bool _Const2>
1779 constexpr bool
1780 __equal(const _Iterator<_Const2>& __i) const
1781 { return __i._M_current == _M_end; }
1782
1783 sentinel_t<_Base> _M_end = sentinel_t<_Base>();
1784
1785 public:
1786 _Sentinel() = default;
1787
1788 constexpr explicit
1789 _Sentinel(sentinel_t<_Base> __end)
1790 : _M_end(__end)
1791 { }
1792
1793 constexpr
1794 _Sentinel(_Sentinel<!_Const> __i)
1795 requires _Const
1796 && convertible_to<sentinel_t<_Vp>, sentinel_t<_Base>>
1797 : _M_end(std::move(__i._M_end))
1798 { }
1799
1800 constexpr sentinel_t<_Base>
1801 base() const
1802 { return _M_end; }
1803
1804 template<bool _Const2>
1805 requires sentinel_for<sentinel_t<_Base>,
1806 iterator_t<__detail::__maybe_const_t<_Const2, _Vp>>>
1807 friend constexpr bool
1808 operator==(const _Iterator<_Const2>& __x, const _Sentinel& __y)
1809 { return __y.__equal(__x); }
1810
1811 template<bool _Const2,
1812 typename _Base2 = __detail::__maybe_const_t<_Const2, _Vp>>
1813 requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<_Base2>>
1814 friend constexpr range_difference_t<_Base2>
1815 operator-(const _Iterator<_Const2>& __x, const _Sentinel& __y)
1816 { return -__y.__distance_from(__x); }
1817
1818 template<bool _Const2,
1819 typename _Base2 = __detail::__maybe_const_t<_Const2, _Vp>>
1820 requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<_Base2>>
1821 friend constexpr range_difference_t<_Base2>
1822 operator-(const _Sentinel& __y, const _Iterator<_Const2>& __x)
1823 { return __y.__distance_from(__x); }
1824
1825 friend _Sentinel<!_Const>;
1826 };
1827
1828 [[no_unique_address]] __detail::__box<_Fp> _M_fun;
1829 _Vp _M_base = _Vp();
1830
1831 public:
1832 transform_view() requires (default_initializable<_Vp>
1833 && default_initializable<_Fp>)
1834 = default;
1835
1836 constexpr
1837 transform_view(_Vp __base, _Fp __fun)
1838 : _M_fun(std::move(__fun)), _M_base(std::move(__base))
1839 { }
1840
1841 constexpr _Vp
1842 base() const& requires copy_constructible<_Vp>
1843 { return _M_base ; }
1844
1845 constexpr _Vp
1846 base() &&
1847 { return std::move(_M_base); }
1848
1849 constexpr _Iterator<false>
1850 begin()
1851 { return _Iterator<false>{this, ranges::begin(_M_base)}; }
1852
1853 constexpr _Iterator<true>
1854 begin() const
1855 requires range<const _Vp>
1856 && regular_invocable<const _Fp&, range_reference_t<const _Vp>>
1857 { return _Iterator<true>{this, ranges::begin(_M_base)}; }
1858
1859 constexpr _Sentinel<false>
1860 end()
1861 { return _Sentinel<false>{ranges::end(_M_base)}; }
1862
1863 constexpr _Iterator<false>
1864 end() requires common_range<_Vp>
1865 { return _Iterator<false>{this, ranges::end(_M_base)}; }
1866
1867 constexpr _Sentinel<true>
1868 end() const
1869 requires range<const _Vp>
1870 && regular_invocable<const _Fp&, range_reference_t<const _Vp>>
1871 { return _Sentinel<true>{ranges::end(_M_base)}; }
1872
1873 constexpr _Iterator<true>
1874 end() const
1875 requires common_range<const _Vp>
1876 && regular_invocable<const _Fp&, range_reference_t<const _Vp>>
1877 { return _Iterator<true>{this, ranges::end(_M_base)}; }
1878
1879 constexpr auto
1880 size() requires sized_range<_Vp>
1881 { return ranges::size(_M_base); }
1882
1883 constexpr auto
1884 size() const requires sized_range<const _Vp>
1885 { return ranges::size(_M_base); }
1886 };
1887
1888 template<typename _Range, typename _Fp>
1889 transform_view(_Range&&, _Fp) -> transform_view<views::all_t<_Range>, _Fp>;
1890
1891 namespace views
1892 {
1893 namespace __detail
1894 {
1895 template<typename _Range, typename _Fp>
1896 concept __can_transform_view
1897 = requires { transform_view(std::declval<_Range>(), std::declval<_Fp>()); };
1898 } // namespace __detail
1899
1900 struct _Transform : __adaptor::_RangeAdaptor<_Transform>
1901 {
1902 template<viewable_range _Range, typename _Fp>
1903 requires __detail::__can_transform_view<_Range, _Fp>
1904 constexpr auto
1905 operator()(_Range&& __r, _Fp&& __f) const
1906 {
1907 return transform_view(std::forward<_Range>(__r), std::forward<_Fp>(__f));
1908 }
1909
1910 using _RangeAdaptor<_Transform>::operator();
1911 static constexpr int _S_arity = 2;
1912 static constexpr bool _S_has_simple_extra_args = true;
1913 };
1914
1915 inline constexpr _Transform transform;
1916 } // namespace views
1917
1918 template<view _Vp>
1919 class take_view : public view_interface<take_view<_Vp>>
1920 {
1921 private:
1922 template<bool _Const>
1923 using _CI = counted_iterator<
1924 iterator_t<__detail::__maybe_const_t<_Const, _Vp>>>;
1925
1926 template<bool _Const>
1927 struct _Sentinel
1928 {
1929 private:
1930 using _Base = __detail::__maybe_const_t<_Const, _Vp>;
1931 sentinel_t<_Base> _M_end = sentinel_t<_Base>();
1932
1933 public:
1934 _Sentinel() = default;
1935
1936 constexpr explicit
1937 _Sentinel(sentinel_t<_Base> __end)
1938 : _M_end(__end)
1939 { }
1940
1941 constexpr
1942 _Sentinel(_Sentinel<!_Const> __s)
1943 requires _Const && convertible_to<sentinel_t<_Vp>, sentinel_t<_Base>>
1944 : _M_end(std::move(__s._M_end))
1945 { }
1946
1947 constexpr sentinel_t<_Base>
1948 base() const
1949 { return _M_end; }
1950
1951 friend constexpr bool
1952 operator==(const _CI<_Const>& __y, const _Sentinel& __x)
1953 { return __y.count() == 0 || __y.base() == __x._M_end; }
1954
1955 template<bool _OtherConst = !_Const,
1956 typename _Base2 = __detail::__maybe_const_t<_OtherConst, _Vp>>
1957 requires sentinel_for<sentinel_t<_Base>, iterator_t<_Base2>>
1958 friend constexpr bool
1959 operator==(const _CI<_OtherConst>& __y, const _Sentinel& __x)
1960 { return __y.count() == 0 || __y.base() == __x._M_end; }
1961
1962 friend _Sentinel<!_Const>;
1963 };
1964
1965 range_difference_t<_Vp> _M_count = 0;
1966 _Vp _M_base = _Vp();
1967
1968 public:
1969 take_view() requires default_initializable<_Vp> = default;
1970
1971 constexpr
1972 take_view(_Vp base, range_difference_t<_Vp> __count)
1973 : _M_count(std::move(__count)), _M_base(std::move(base))
1974 { }
1975
1976 constexpr _Vp
1977 base() const& requires copy_constructible<_Vp>
1978 { return _M_base; }
1979
1980 constexpr _Vp
1981 base() &&
1982 { return std::move(_M_base); }
1983
1984 constexpr auto
1985 begin() requires (!__detail::__simple_view<_Vp>)
1986 {
1987 if constexpr (sized_range<_Vp>)
1988 {
1989 if constexpr (random_access_range<_Vp>)
1990 return ranges::begin(_M_base);
1991 else
1992 {
1993 auto __sz = size();
1994 return counted_iterator(ranges::begin(_M_base), __sz);
1995 }
1996 }
1997 else
1998 return counted_iterator(ranges::begin(_M_base), _M_count);
1999 }
2000
2001 constexpr auto
2002 begin() const requires range<const _Vp>
2003 {
2004 if constexpr (sized_range<const _Vp>)
2005 {
2006 if constexpr (random_access_range<const _Vp>)
2007 return ranges::begin(_M_base);
2008 else
2009 {
2010 auto __sz = size();
2011 return counted_iterator(ranges::begin(_M_base), __sz);
2012 }
2013 }
2014 else
2015 return counted_iterator(ranges::begin(_M_base), _M_count);
2016 }
2017
2018 constexpr auto
2019 end() requires (!__detail::__simple_view<_Vp>)
2020 {
2021 if constexpr (sized_range<_Vp>)
2022 {
2023 if constexpr (random_access_range<_Vp>)
2024 return ranges::begin(_M_base) + size();
2025 else
2026 return default_sentinel;
2027 }
2028 else
2029 return _Sentinel<false>{ranges::end(_M_base)};
2030 }
2031
2032 constexpr auto
2033 end() const requires range<const _Vp>
2034 {
2035 if constexpr (sized_range<const _Vp>)
2036 {
2037 if constexpr (random_access_range<const _Vp>)
2038 return ranges::begin(_M_base) + size();
2039 else
2040 return default_sentinel;
2041 }
2042 else
2043 return _Sentinel<true>{ranges::end(_M_base)};
2044 }
2045
2046 constexpr auto
2047 size() requires sized_range<_Vp>
2048 {
2049 auto __n = ranges::size(_M_base);
2050 return std::min(__n, static_cast<decltype(__n)>(_M_count));
2051 }
2052
2053 constexpr auto
2054 size() const requires sized_range<const _Vp>
2055 {
2056 auto __n = ranges::size(_M_base);
2057 return std::min(__n, static_cast<decltype(__n)>(_M_count));
2058 }
2059 };
2060
2061 // _GLIBCXX_RESOLVE_LIB_DEFECTS
2062 // 3447. Deduction guides for take_view and drop_view have different
2063 // constraints
2064 template<typename _Range>
2065 take_view(_Range&&, range_difference_t<_Range>)
2066 -> take_view<views::all_t<_Range>>;
2067
2068 template<typename _Tp>
2069 inline constexpr bool enable_borrowed_range<take_view<_Tp>>
2070 = enable_borrowed_range<_Tp>;
2071
2072 namespace views
2073 {
2074 namespace __detail
2075 {
2076 template<typename _Range, typename _Tp>
2077 concept __can_take_view
2078 = requires { take_view(std::declval<_Range>(), std::declval<_Tp>()); };
2079 } // namespace __detail
2080
2081 struct _Take : __adaptor::_RangeAdaptor<_Take>
2082 {
2083 template<viewable_range _Range, typename _Tp>
2084 requires __detail::__can_take_view<_Range, _Tp>
2085 constexpr auto
2086 operator()(_Range&& __r, _Tp&& __n) const
2087 {
2088 return take_view(std::forward<_Range>(__r), std::forward<_Tp>(__n));
2089 }
2090
2091 using _RangeAdaptor<_Take>::operator();
2092 static constexpr int _S_arity = 2;
2093 // The count argument of views::take is not always simple -- it can be
2094 // e.g. a move-only class that's implicitly convertible to the difference
2095 // type. But an integer-like count argument is surely simple.
2096 template<typename _Tp>
2097 static constexpr bool _S_has_simple_extra_args
2098 = ranges::__detail::__is_integer_like<_Tp>;
2099 };
2100
2101 inline constexpr _Take take;
2102 } // namespace views
2103
2104 template<view _Vp, typename _Pred>
2105 requires input_range<_Vp> && is_object_v<_Pred>
2106 && indirect_unary_predicate<const _Pred, iterator_t<_Vp>>
2107 class take_while_view : public view_interface<take_while_view<_Vp, _Pred>>
2108 {
2109 template<bool _Const>
2110 struct _Sentinel
2111 {
2112 private:
2113 using _Base = __detail::__maybe_const_t<_Const, _Vp>;
2114
2115 sentinel_t<_Base> _M_end = sentinel_t<_Base>();
2116 const _Pred* _M_pred = nullptr;
2117
2118 public:
2119 _Sentinel() = default;
2120
2121 constexpr explicit
2122 _Sentinel(sentinel_t<_Base> __end, const _Pred* __pred)
2123 : _M_end(__end), _M_pred(__pred)
2124 { }
2125
2126 constexpr
2127 _Sentinel(_Sentinel<!_Const> __s)
2128 requires _Const && convertible_to<sentinel_t<_Vp>, sentinel_t<_Base>>
2129 : _M_end(__s._M_end), _M_pred(__s._M_pred)
2130 { }
2131
2132 constexpr sentinel_t<_Base>
2133 base() const { return _M_end; }
2134
2135 friend constexpr bool
2136 operator==(const iterator_t<_Base>& __x, const _Sentinel& __y)
2137 { return __y._M_end == __x || !std::__invoke(*__y._M_pred, *__x); }
2138
2139 template<bool _OtherConst = !_Const,
2140 typename _Base2 = __detail::__maybe_const_t<_OtherConst, _Vp>>
2141 requires sentinel_for<sentinel_t<_Base>, iterator_t<_Base2>>
2142 friend constexpr bool
2143 operator==(const iterator_t<_Base2>& __x, const _Sentinel& __y)
2144 { return __y._M_end == __x || !std::__invoke(*__y._M_pred, *__x); }
2145
2146 friend _Sentinel<!_Const>;
2147 };
2148
2149 [[no_unique_address]] __detail::__box<_Pred> _M_pred;
2150 _Vp _M_base = _Vp();
2151
2152 public:
2153 take_while_view() requires (default_initializable<_Vp>
2154 && default_initializable<_Pred>)
2155 = default;
2156
2157 constexpr
2158 take_while_view(_Vp base, _Pred __pred)
2159 : _M_pred(std::move(__pred)), _M_base(std::move(base))
2160 { }
2161
2162 constexpr _Vp
2163 base() const& requires copy_constructible<_Vp>
2164 { return _M_base; }
2165
2166 constexpr _Vp
2167 base() &&
2168 { return std::move(_M_base); }
2169
2170 constexpr const _Pred&
2171 pred() const
2172 { return *_M_pred; }
2173
2174 constexpr auto
2175 begin() requires (!__detail::__simple_view<_Vp>)
2176 { return ranges::begin(_M_base); }
2177
2178 constexpr auto
2179 begin() const requires range<const _Vp>
2180 && indirect_unary_predicate<const _Pred, iterator_t<const _Vp>>
2181 { return ranges::begin(_M_base); }
2182
2183 constexpr auto
2184 end() requires (!__detail::__simple_view<_Vp>)
2185 { return _Sentinel<false>(ranges::end(_M_base),
2186 std::__addressof(*_M_pred)); }
2187
2188 constexpr auto
2189 end() const requires range<const _Vp>
2190 && indirect_unary_predicate<const _Pred, iterator_t<const _Vp>>
2191 { return _Sentinel<true>(ranges::end(_M_base),
2192 std::__addressof(*_M_pred)); }
2193 };
2194
2195 template<typename _Range, typename _Pred>
2196 take_while_view(_Range&&, _Pred)
2197 -> take_while_view<views::all_t<_Range>, _Pred>;
2198
2199 namespace views
2200 {
2201 namespace __detail
2202 {
2203 template<typename _Range, typename _Pred>
2204 concept __can_take_while_view
2205 = requires { take_while_view(std::declval<_Range>(), std::declval<_Pred>()); };
2206 } // namespace __detail
2207
2208 struct _TakeWhile : __adaptor::_RangeAdaptor<_TakeWhile>
2209 {
2210 template<viewable_range _Range, typename _Pred>
2211 requires __detail::__can_take_while_view<_Range, _Pred>
2212 constexpr auto
2213 operator()(_Range&& __r, _Pred&& __p) const
2214 {
2215 return take_while_view(std::forward<_Range>(__r), std::forward<_Pred>(__p));
2216 }
2217
2218 using _RangeAdaptor<_TakeWhile>::operator();
2219 static constexpr int _S_arity = 2;
2220 static constexpr bool _S_has_simple_extra_args = true;
2221 };
2222
2223 inline constexpr _TakeWhile take_while;
2224 } // namespace views
2225
2226 template<view _Vp>
2227 class drop_view : public view_interface<drop_view<_Vp>>
2228 {
2229 private:
2230 range_difference_t<_Vp> _M_count = 0;
2231 _Vp _M_base = _Vp();
2232
2233 // ranges::next(begin(base), count, end(base)) is O(1) if _Vp satisfies
2234 // both random_access_range and sized_range. Otherwise, cache its result.
2235 static constexpr bool _S_needs_cached_begin
2236 = !(random_access_range<const _Vp> && sized_range<const _Vp>);
2237 [[no_unique_address]]
2238 __detail::__maybe_present_t<_S_needs_cached_begin,
2239 __detail::_CachedPosition<_Vp>>
2240 _M_cached_begin;
2241
2242 public:
2243 drop_view() requires default_initializable<_Vp> = default;
2244
2245 constexpr
2246 drop_view(_Vp __base, range_difference_t<_Vp> __count)
2247 : _M_count(__count), _M_base(std::move(__base))
2248 { __glibcxx_assert(__count >= 0); }
2249
2250 constexpr _Vp
2251 base() const& requires copy_constructible<_Vp>
2252 { return _M_base; }
2253
2254 constexpr _Vp
2255 base() &&
2256 { return std::move(_M_base); }
2257
2258 // This overload is disabled for simple views with constant-time begin().
2259 constexpr auto
2260 begin()
2261 requires (!(__detail::__simple_view<_Vp>
2262 && random_access_range<const _Vp>
2263 && sized_range<const _Vp>))
2264 {
2265 if constexpr (_S_needs_cached_begin)
2266 if (_M_cached_begin._M_has_value())
2267 return _M_cached_begin._M_get(_M_base);
2268
2269 auto __it = ranges::next(ranges::begin(_M_base),
2270 _M_count, ranges::end(_M_base));
2271 if constexpr (_S_needs_cached_begin)
2272 _M_cached_begin._M_set(_M_base, __it);
2273 return __it;
2274 }
2275
2276 // _GLIBCXX_RESOLVE_LIB_DEFECTS
2277 // 3482. drop_view's const begin should additionally require sized_range
2278 constexpr auto
2279 begin() const
2280 requires random_access_range<const _Vp> && sized_range<const _Vp>
2281 {
2282 return ranges::next(ranges::begin(_M_base), _M_count,
2283 ranges::end(_M_base));
2284 }
2285
2286 constexpr auto
2287 end() requires (!__detail::__simple_view<_Vp>)
2288 { return ranges::end(_M_base); }
2289
2290 constexpr auto
2291 end() const requires range<const _Vp>
2292 { return ranges::end(_M_base); }
2293
2294 constexpr auto
2295 size() requires sized_range<_Vp>
2296 {
2297 const auto __s = ranges::size(_M_base);
2298 const auto __c = static_cast<decltype(__s)>(_M_count);
2299 return __s < __c ? 0 : __s - __c;
2300 }
2301
2302 constexpr auto
2303 size() const requires sized_range<const _Vp>
2304 {
2305 const auto __s = ranges::size(_M_base);
2306 const auto __c = static_cast<decltype(__s)>(_M_count);
2307 return __s < __c ? 0 : __s - __c;
2308 }
2309 };
2310
2311 template<typename _Range>
2312 drop_view(_Range&&, range_difference_t<_Range>)
2313 -> drop_view<views::all_t<_Range>>;
2314
2315 template<typename _Tp>
2316 inline constexpr bool enable_borrowed_range<drop_view<_Tp>>
2317 = enable_borrowed_range<_Tp>;
2318
2319 namespace views
2320 {
2321 namespace __detail
2322 {
2323 template<typename _Range, typename _Tp>
2324 concept __can_drop_view
2325 = requires { drop_view(std::declval<_Range>(), std::declval<_Tp>()); };
2326 } // namespace __detail
2327
2328 struct _Drop : __adaptor::_RangeAdaptor<_Drop>
2329 {
2330 template<viewable_range _Range, typename _Tp>
2331 requires __detail::__can_drop_view<_Range, _Tp>
2332 constexpr auto
2333 operator()(_Range&& __r, _Tp&& __n) const
2334 {
2335 return drop_view(std::forward<_Range>(__r), std::forward<_Tp>(__n));
2336 }
2337
2338 using _RangeAdaptor<_Drop>::operator();
2339 static constexpr int _S_arity = 2;
2340 template<typename _Tp>
2341 static constexpr bool _S_has_simple_extra_args
2342 = _Take::_S_has_simple_extra_args<_Tp>;
2343 };
2344
2345 inline constexpr _Drop drop;
2346 } // namespace views
2347
2348 template<view _Vp, typename _Pred>
2349 requires input_range<_Vp> && is_object_v<_Pred>
2350 && indirect_unary_predicate<const _Pred, iterator_t<_Vp>>
2351 class drop_while_view : public view_interface<drop_while_view<_Vp, _Pred>>
2352 {
2353 private:
2354 [[no_unique_address]] __detail::__box<_Pred> _M_pred;
2355 [[no_unique_address]] __detail::_CachedPosition<_Vp> _M_cached_begin;
2356 _Vp _M_base = _Vp();
2357
2358 public:
2359 drop_while_view() requires (default_initializable<_Vp>
2360 && default_initializable<_Pred>)
2361 = default;
2362
2363 constexpr
2364 drop_while_view(_Vp __base, _Pred __pred)
2365 : _M_pred(std::move(__pred)), _M_base(std::move(__base))
2366 { }
2367
2368 constexpr _Vp
2369 base() const& requires copy_constructible<_Vp>
2370 { return _M_base; }
2371
2372 constexpr _Vp
2373 base() &&
2374 { return std::move(_M_base); }
2375
2376 constexpr const _Pred&
2377 pred() const
2378 { return *_M_pred; }
2379
2380 constexpr auto
2381 begin()
2382 {
2383 if (_M_cached_begin._M_has_value())
2384 return _M_cached_begin._M_get(_M_base);
2385
2386 __glibcxx_assert(_M_pred.has_value());
2387 auto __it = ranges::find_if_not(ranges::begin(_M_base),
2388 ranges::end(_M_base),
2389 std::cref(*_M_pred));
2390 _M_cached_begin._M_set(_M_base, __it);
2391 return __it;
2392 }
2393
2394 constexpr auto
2395 end()
2396 { return ranges::end(_M_base); }
2397 };
2398
2399 template<typename _Range, typename _Pred>
2400 drop_while_view(_Range&&, _Pred)
2401 -> drop_while_view<views::all_t<_Range>, _Pred>;
2402
2403 template<typename _Tp, typename _Pred>
2404 inline constexpr bool enable_borrowed_range<drop_while_view<_Tp, _Pred>>
2405 = enable_borrowed_range<_Tp>;
2406
2407 namespace views
2408 {
2409 namespace __detail
2410 {
2411 template<typename _Range, typename _Pred>
2412 concept __can_drop_while_view
2413 = requires { drop_while_view(std::declval<_Range>(), std::declval<_Pred>()); };
2414 } // namespace __detail
2415
2416 struct _DropWhile : __adaptor::_RangeAdaptor<_DropWhile>
2417 {
2418 template<viewable_range _Range, typename _Pred>
2419 requires __detail::__can_drop_while_view<_Range, _Pred>
2420 constexpr auto
2421 operator()(_Range&& __r, _Pred&& __p) const
2422 {
2423 return drop_while_view(std::forward<_Range>(__r),
2424 std::forward<_Pred>(__p));
2425 }
2426
2427 using _RangeAdaptor<_DropWhile>::operator();
2428 static constexpr int _S_arity = 2;
2429 static constexpr bool _S_has_simple_extra_args = true;
2430 };
2431
2432 inline constexpr _DropWhile drop_while;
2433 } // namespace views
2434
2435 template<input_range _Vp>
2436 requires view<_Vp> && input_range<range_reference_t<_Vp>>
2437 class join_view : public view_interface<join_view<_Vp>>
2438 {
2439 private:
2440 using _InnerRange = range_reference_t<_Vp>;
2441
2442 template<bool _Const>
2443 using _Base = __detail::__maybe_const_t<_Const, _Vp>;
2444
2445 template<bool _Const>
2446 using _Outer_iter = iterator_t<_Base<_Const>>;
2447
2448 template<bool _Const>
2449 using _Inner_iter = iterator_t<range_reference_t<_Base<_Const>>>;
2450
2451 template<bool _Const>
2452 static constexpr bool _S_ref_is_glvalue
2453 = is_reference_v<range_reference_t<_Base<_Const>>>;
2454
2455 template<bool _Const>
2456 struct __iter_cat
2457 { };
2458
2459 template<bool _Const>
2460 requires _S_ref_is_glvalue<_Const>
2461 && forward_range<_Base<_Const>>
2462 && forward_range<range_reference_t<_Base<_Const>>>
2463 struct __iter_cat<_Const>
2464 {
2465 private:
2466 static constexpr auto
2467 _S_iter_cat()
2468 {
2469 using _Outer_iter = join_view::_Outer_iter<_Const>;
2470 using _Inner_iter = join_view::_Inner_iter<_Const>;
2471 using _OuterCat = typename iterator_traits<_Outer_iter>::iterator_category;
2472 using _InnerCat = typename iterator_traits<_Inner_iter>::iterator_category;
2473 if constexpr (derived_from<_OuterCat, bidirectional_iterator_tag>
2474 && derived_from<_InnerCat, bidirectional_iterator_tag>
2475 && common_range<range_reference_t<_Base<_Const>>>)
2476 return bidirectional_iterator_tag{};
2477 else if constexpr (derived_from<_OuterCat, forward_iterator_tag>
2478 && derived_from<_InnerCat, forward_iterator_tag>)
2479 return forward_iterator_tag{};
2480 else
2481 return input_iterator_tag{};
2482 }
2483 public:
2484 using iterator_category = decltype(_S_iter_cat());
2485 };
2486
2487 template<bool _Const>
2488 struct _Sentinel;
2489
2490 template<bool _Const>
2491 struct _Iterator : __iter_cat<_Const>
2492 {
2493 private:
2494 using _Parent = __detail::__maybe_const_t<_Const, join_view>;
2495 using _Base = join_view::_Base<_Const>;
2496
2497 static constexpr bool _S_ref_is_glvalue
2498 = join_view::_S_ref_is_glvalue<_Const>;
2499
2500 constexpr void
2501 _M_satisfy()
2502 {
2503 auto __update_inner = [this] (const iterator_t<_Base>& __x) -> auto&& {
2504 if constexpr (_S_ref_is_glvalue)
2505 return *__x;
2506 else
2507 return _M_parent->_M_inner._M_emplace_deref(__x);
2508 };
2509
2510 for (; _M_outer != ranges::end(_M_parent->_M_base); ++_M_outer)
2511 {
2512 auto&& __inner = __update_inner(_M_outer);
2513 _M_inner = ranges::begin(__inner);
2514 if (_M_inner != ranges::end(__inner))
2515 return;
2516 }
2517
2518 if constexpr (_S_ref_is_glvalue)
2519 _M_inner = _Inner_iter();
2520 }
2521
2522 static constexpr auto
2523 _S_iter_concept()
2524 {
2525 if constexpr (_S_ref_is_glvalue
2526 && bidirectional_range<_Base>
2527 && bidirectional_range<range_reference_t<_Base>>
2528 && common_range<range_reference_t<_Base>>)
2529 return bidirectional_iterator_tag{};
2530 else if constexpr (_S_ref_is_glvalue
2531 && forward_range<_Base>
2532 && forward_range<range_reference_t<_Base>>)
2533 return forward_iterator_tag{};
2534 else
2535 return input_iterator_tag{};
2536 }
2537
2538 using _Outer_iter = join_view::_Outer_iter<_Const>;
2539 using _Inner_iter = join_view::_Inner_iter<_Const>;
2540
2541 _Outer_iter _M_outer = _Outer_iter();
2542 _Inner_iter _M_inner = _Inner_iter();
2543 _Parent* _M_parent = nullptr;
2544
2545 public:
2546 using iterator_concept = decltype(_S_iter_concept());
2547 // iterator_category defined in __join_view_iter_cat
2548 using value_type = range_value_t<range_reference_t<_Base>>;
2549 using difference_type
2550 = common_type_t<range_difference_t<_Base>,
2551 range_difference_t<range_reference_t<_Base>>>;
2552
2553 _Iterator() requires (default_initializable<_Outer_iter>
2554 && default_initializable<_Inner_iter>)
2555 = default;
2556
2557 constexpr
2558 _Iterator(_Parent* __parent, _Outer_iter __outer)
2559 : _M_outer(std::move(__outer)),
2560 _M_parent(__parent)
2561 { _M_satisfy(); }
2562
2563 constexpr
2564 _Iterator(_Iterator<!_Const> __i)
2565 requires _Const
2566 && convertible_to<iterator_t<_Vp>, _Outer_iter>
2567 && convertible_to<iterator_t<_InnerRange>, _Inner_iter>
2568 : _M_outer(std::move(__i._M_outer)), _M_inner(std::move(__i._M_inner)),
2569 _M_parent(__i._M_parent)
2570 { }
2571
2572 constexpr decltype(auto)
2573 operator*() const
2574 { return *_M_inner; }
2575
2576 // _GLIBCXX_RESOLVE_LIB_DEFECTS
2577 // 3500. join_view::iterator::operator->() is bogus
2578 constexpr _Inner_iter
2579 operator->() const
2580 requires __detail::__has_arrow<_Inner_iter>
2581 && copyable<_Inner_iter>
2582 { return _M_inner; }
2583
2584 constexpr _Iterator&
2585 operator++()
2586 {
2587 auto&& __inner_range = [this] () -> auto&& {
2588 if constexpr (_S_ref_is_glvalue)
2589 return *_M_outer;
2590 else
2591 return *_M_parent->_M_inner;
2592 }();
2593 if (++_M_inner == ranges::end(__inner_range))
2594 {
2595 ++_M_outer;
2596 _M_satisfy();
2597 }
2598 return *this;
2599 }
2600
2601 constexpr void
2602 operator++(int)
2603 { ++*this; }
2604
2605 constexpr _Iterator
2606 operator++(int)
2607 requires _S_ref_is_glvalue && forward_range<_Base>
2608 && forward_range<range_reference_t<_Base>>
2609 {
2610 auto __tmp = *this;
2611 ++*this;
2612 return __tmp;
2613 }
2614
2615 constexpr _Iterator&
2616 operator--()
2617 requires _S_ref_is_glvalue && bidirectional_range<_Base>
2618 && bidirectional_range<range_reference_t<_Base>>
2619 && common_range<range_reference_t<_Base>>
2620 {
2621 if (_M_outer == ranges::end(_M_parent->_M_base))
2622 _M_inner = ranges::end(*--_M_outer);
2623 while (_M_inner == ranges::begin(*_M_outer))
2624 _M_inner = ranges::end(*--_M_outer);
2625 --_M_inner;
2626 return *this;
2627 }
2628
2629 constexpr _Iterator
2630 operator--(int)
2631 requires _S_ref_is_glvalue && bidirectional_range<_Base>
2632 && bidirectional_range<range_reference_t<_Base>>
2633 && common_range<range_reference_t<_Base>>
2634 {
2635 auto __tmp = *this;
2636 --*this;
2637 return __tmp;
2638 }
2639
2640 friend constexpr bool
2641 operator==(const _Iterator& __x, const _Iterator& __y)
2642 requires _S_ref_is_glvalue
2643 && equality_comparable<_Outer_iter>
2644 && equality_comparable<_Inner_iter>
2645 {
2646 return (__x._M_outer == __y._M_outer
2647 && __x._M_inner == __y._M_inner);
2648 }
2649
2650 friend constexpr decltype(auto)
2651 iter_move(const _Iterator& __i)
2652 noexcept(noexcept(ranges::iter_move(__i._M_inner)))
2653 { return ranges::iter_move(__i._M_inner); }
2654
2655 friend constexpr void
2656 iter_swap(const _Iterator& __x, const _Iterator& __y)
2657 noexcept(noexcept(ranges::iter_swap(__x._M_inner, __y._M_inner)))
2658 requires indirectly_swappable<_Inner_iter>
2659 { return ranges::iter_swap(__x._M_inner, __y._M_inner); }
2660
2661 friend _Iterator<!_Const>;
2662 template<bool> friend struct _Sentinel;
2663 };
2664
2665 template<bool _Const>
2666 struct _Sentinel
2667 {
2668 private:
2669 using _Parent = __detail::__maybe_const_t<_Const, join_view>;
2670 using _Base = join_view::_Base<_Const>;
2671
2672 template<bool _Const2>
2673 constexpr bool
2674 __equal(const _Iterator<_Const2>& __i) const
2675 { return __i._M_outer == _M_end; }
2676
2677 sentinel_t<_Base> _M_end = sentinel_t<_Base>();
2678
2679 public:
2680 _Sentinel() = default;
2681
2682 constexpr explicit
2683 _Sentinel(_Parent* __parent)
2684 : _M_end(ranges::end(__parent->_M_base))
2685 { }
2686
2687 constexpr
2688 _Sentinel(_Sentinel<!_Const> __s)
2689 requires _Const && convertible_to<sentinel_t<_Vp>, sentinel_t<_Base>>
2690 : _M_end(std::move(__s._M_end))
2691 { }
2692
2693 template<bool _Const2>
2694 requires sentinel_for<sentinel_t<_Base>,
2695 iterator_t<__detail::__maybe_const_t<_Const2, _Vp>>>
2696 friend constexpr bool
2697 operator==(const _Iterator<_Const2>& __x, const _Sentinel& __y)
2698 { return __y.__equal(__x); }
2699
2700 friend _Sentinel<!_Const>;
2701 };
2702
2703 [[no_unique_address]]
2704 __detail::__non_propagating_cache<remove_cv_t<_InnerRange>> _M_inner;
2705 _Vp _M_base = _Vp();
2706
2707 public:
2708 join_view() requires default_initializable<_Vp> = default;
2709
2710 constexpr explicit
2711 join_view(_Vp __base)
2712 : _M_base(std::move(__base))
2713 { }
2714
2715 constexpr _Vp
2716 base() const& requires copy_constructible<_Vp>
2717 { return _M_base; }
2718
2719 constexpr _Vp
2720 base() &&
2721 { return std::move(_M_base); }
2722
2723 constexpr auto
2724 begin()
2725 {
2726 constexpr bool __use_const
2727 = (__detail::__simple_view<_Vp>
2728 && is_reference_v<range_reference_t<_Vp>>);
2729 return _Iterator<__use_const>{this, ranges::begin(_M_base)};
2730 }
2731
2732 constexpr auto
2733 begin() const
2734 requires input_range<const _Vp>
2735 && is_reference_v<range_reference_t<const _Vp>>
2736 {
2737 return _Iterator<true>{this, ranges::begin(_M_base)};
2738 }
2739
2740 constexpr auto
2741 end()
2742 {
2743 if constexpr (forward_range<_Vp> && is_reference_v<_InnerRange>
2744 && forward_range<_InnerRange>
2745 && common_range<_Vp> && common_range<_InnerRange>)
2746 return _Iterator<__detail::__simple_view<_Vp>>{this,
2747 ranges::end(_M_base)};
2748 else
2749 return _Sentinel<__detail::__simple_view<_Vp>>{this};
2750 }
2751
2752 constexpr auto
2753 end() const
2754 requires input_range<const _Vp>
2755 && is_reference_v<range_reference_t<const _Vp>>
2756 {
2757 if constexpr (forward_range<const _Vp>
2758 && is_reference_v<range_reference_t<const _Vp>>
2759 && forward_range<range_reference_t<const _Vp>>
2760 && common_range<const _Vp>
2761 && common_range<range_reference_t<const _Vp>>)
2762 return _Iterator<true>{this, ranges::end(_M_base)};
2763 else
2764 return _Sentinel<true>{this};
2765 }
2766 };
2767
2768 template<typename _Range>
2769 explicit join_view(_Range&&) -> join_view<views::all_t<_Range>>;
2770
2771 namespace views
2772 {
2773 namespace __detail
2774 {
2775 template<typename _Range>
2776 concept __can_join_view
2777 = requires { join_view<all_t<_Range>>{std::declval<_Range>()}; };
2778 } // namespace __detail
2779
2780 struct _Join : __adaptor::_RangeAdaptorClosure
2781 {
2782 template<viewable_range _Range>
2783 requires __detail::__can_join_view<_Range>
2784 constexpr auto
2785 operator()(_Range&& __r) const
2786 {
2787 // _GLIBCXX_RESOLVE_LIB_DEFECTS
2788 // 3474. Nesting join_views is broken because of CTAD
2789 return join_view<all_t<_Range>>{std::forward<_Range>(__r)};
2790 }
2791
2792 static constexpr bool _S_has_simple_call_op = true;
2793 };
2794
2795 inline constexpr _Join join;
2796 } // namespace views
2797
2798 namespace __detail
2799 {
2800 template<auto>
2801 struct __require_constant;
2802
2803 template<typename _Range>
2804 concept __tiny_range = sized_range<_Range>
2805 && requires
2806 { typename __require_constant<remove_reference_t<_Range>::size()>; }
2807 && (remove_reference_t<_Range>::size() <= 1);
2808
2809 template<typename _Base>
2810 struct __split_view_outer_iter_cat
2811 { };
2812
2813 template<forward_range _Base>
2814 struct __split_view_outer_iter_cat<_Base>
2815 { using iterator_category = input_iterator_tag; };
2816
2817 template<typename _Base>
2818 struct __split_view_inner_iter_cat
2819 { };
2820
2821 template<forward_range _Base>
2822 struct __split_view_inner_iter_cat<_Base>
2823 {
2824 private:
2825 static constexpr auto
2826 _S_iter_cat()
2827 {
2828 using _Cat = typename iterator_traits<iterator_t<_Base>>::iterator_category;
2829 if constexpr (derived_from<_Cat, forward_iterator_tag>)
2830 return forward_iterator_tag{};
2831 else
2832 return _Cat{};
2833 }
2834 public:
2835 using iterator_category = decltype(_S_iter_cat());
2836 };
2837 }
2838
2839 template<input_range _Vp, forward_range _Pattern>
2840 requires view<_Vp> && view<_Pattern>
2841 && indirectly_comparable<iterator_t<_Vp>, iterator_t<_Pattern>,
2842 ranges::equal_to>
2843 && (forward_range<_Vp> || __detail::__tiny_range<_Pattern>)
2844 class split_view : public view_interface<split_view<_Vp, _Pattern>>
2845 {
2846 private:
2847 template<bool _Const>
2848 using _Base = __detail::__maybe_const_t<_Const, _Vp>;
2849
2850 template<bool _Const>
2851 struct _InnerIter;
2852
2853 template<bool _Const>
2854 struct _OuterIter
2855 : __detail::__split_view_outer_iter_cat<_Base<_Const>>
2856 {
2857 private:
2858 using _Parent = __detail::__maybe_const_t<_Const, split_view>;
2859 using _Base = split_view::_Base<_Const>;
2860
2861 constexpr bool
2862 __at_end() const
2863 { return __current() == ranges::end(_M_parent->_M_base); }
2864
2865 // [range.split.outer] p1
2866 // Many of the following specifications refer to the notional member
2867 // current of outer-iterator. current is equivalent to current_ if
2868 // V models forward_range, and parent_->current_ otherwise.
2869 constexpr auto&
2870 __current() noexcept
2871 {
2872 if constexpr (forward_range<_Vp>)
2873 return _M_current;
2874 else
2875 return _M_parent->_M_current;
2876 }
2877
2878 constexpr auto&
2879 __current() const noexcept
2880 {
2881 if constexpr (forward_range<_Vp>)
2882 return _M_current;
2883 else
2884 return _M_parent->_M_current;
2885 }
2886
2887 _Parent* _M_parent = nullptr;
2888
2889 // XXX: _M_current is present only if "V models forward_range"
2890 [[no_unique_address]]
2891 __detail::__maybe_present_t<forward_range<_Vp>,
2892 iterator_t<_Base>> _M_current;
2893
2894 public:
2895 using iterator_concept = conditional_t<forward_range<_Base>,
2896 forward_iterator_tag,
2897 input_iterator_tag>;
2898 // iterator_category defined in __split_view_outer_iter_cat
2899 using difference_type = range_difference_t<_Base>;
2900
2901 struct value_type : view_interface<value_type>
2902 {
2903 private:
2904 _OuterIter _M_i = _OuterIter();
2905
2906 public:
2907 value_type() = default;
2908
2909 constexpr explicit
2910 value_type(_OuterIter __i)
2911 : _M_i(std::move(__i))
2912 { }
2913
2914 constexpr _InnerIter<_Const>
2915 begin() const
2916 { return _InnerIter<_Const>{_M_i}; }
2917
2918 constexpr default_sentinel_t
2919 end() const noexcept
2920 { return default_sentinel; }
2921 };
2922
2923 _OuterIter() = default;
2924
2925 constexpr explicit
2926 _OuterIter(_Parent* __parent) requires (!forward_range<_Base>)
2927 : _M_parent(__parent)
2928 { }
2929
2930 constexpr
2931 _OuterIter(_Parent* __parent, iterator_t<_Base> __current)
2932 requires forward_range<_Base>
2933 : _M_parent(__parent),
2934 _M_current(std::move(__current))
2935 { }
2936
2937 constexpr
2938 _OuterIter(_OuterIter<!_Const> __i)
2939 requires _Const
2940 && convertible_to<iterator_t<_Vp>, iterator_t<_Base>>
2941 : _M_parent(__i._M_parent), _M_current(std::move(__i._M_current))
2942 { }
2943
2944 constexpr value_type
2945 operator*() const
2946 { return value_type{*this}; }
2947
2948 constexpr _OuterIter&
2949 operator++()
2950 {
2951 // _GLIBCXX_RESOLVE_LIB_DEFECTS
2952 // 3505. split_view::outer-iterator::operator++ misspecified
2953 const auto __end = ranges::end(_M_parent->_M_base);
2954 if (__current() == __end)
2955 return *this;
2956 const auto [__pbegin, __pend] = subrange{_M_parent->_M_pattern};
2957 if (__pbegin == __pend)
2958 ++__current();
2959 else if constexpr (__detail::__tiny_range<_Pattern>)
2960 {
2961 __current() = ranges::find(std::move(__current()), __end,
2962 *__pbegin);
2963 if (__current() != __end)
2964 ++__current();
2965 }
2966 else
2967 do
2968 {
2969 auto [__b, __p]
2970 = ranges::mismatch(__current(), __end, __pbegin, __pend);
2971 if (__p == __pend)
2972 {
2973 __current() = __b;
2974 break;
2975 }
2976 } while (++__current() != __end);
2977 return *this;
2978 }
2979
2980 constexpr decltype(auto)
2981 operator++(int)
2982 {
2983 if constexpr (forward_range<_Base>)
2984 {
2985 auto __tmp = *this;
2986 ++*this;
2987 return __tmp;
2988 }
2989 else
2990 ++*this;
2991 }
2992
2993 friend constexpr bool
2994 operator==(const _OuterIter& __x, const _OuterIter& __y)
2995 requires forward_range<_Base>
2996 { return __x._M_current == __y._M_current; }
2997
2998 friend constexpr bool
2999 operator==(const _OuterIter& __x, default_sentinel_t)
3000 { return __x.__at_end(); };
3001
3002 friend _OuterIter<!_Const>;
3003 friend _InnerIter<_Const>;
3004 };
3005
3006 template<bool _Const>
3007 struct _InnerIter
3008 : __detail::__split_view_inner_iter_cat<_Base<_Const>>
3009 {
3010 private:
3011 using _Base = split_view::_Base<_Const>;
3012
3013 constexpr bool
3014 __at_end() const
3015 {
3016 auto [__pcur, __pend] = subrange{_M_i._M_parent->_M_pattern};
3017 auto __end = ranges::end(_M_i._M_parent->_M_base);
3018 if constexpr (__detail::__tiny_range<_Pattern>)
3019 {
3020 const auto& __cur = _M_i_current();
3021 if (__cur == __end)
3022 return true;
3023 if (__pcur == __pend)
3024 return _M_incremented;
3025 return *__cur == *__pcur;
3026 }
3027 else
3028 {
3029 auto __cur = _M_i_current();
3030 if (__cur == __end)
3031 return true;
3032 if (__pcur == __pend)
3033 return _M_incremented;
3034 do
3035 {
3036 if (*__cur != *__pcur)
3037 return false;
3038 if (++__pcur == __pend)
3039 return true;
3040 } while (++__cur != __end);
3041 return false;
3042 }
3043 }
3044
3045 constexpr auto&
3046 _M_i_current() noexcept
3047 { return _M_i.__current(); }
3048
3049 constexpr auto&
3050 _M_i_current() const noexcept
3051 { return _M_i.__current(); }
3052
3053 _OuterIter<_Const> _M_i = _OuterIter<_Const>();
3054 bool _M_incremented = false;
3055
3056 public:
3057 using iterator_concept
3058 = typename _OuterIter<_Const>::iterator_concept;
3059 // iterator_category defined in __split_view_inner_iter_cat
3060 using value_type = range_value_t<_Base>;
3061 using difference_type = range_difference_t<_Base>;
3062
3063 _InnerIter() = default;
3064
3065 constexpr explicit
3066 _InnerIter(_OuterIter<_Const> __i)
3067 : _M_i(std::move(__i))
3068 { }
3069
3070 constexpr const iterator_t<_Base>&
3071 base() const& noexcept
3072 { return _M_i_current(); }
3073
3074 constexpr iterator_t<_Base>
3075 base() && requires forward_range<_Vp>
3076 { return std::move(_M_i_current()); }
3077
3078 constexpr decltype(auto)
3079 operator*() const
3080 { return *_M_i_current(); }
3081
3082 constexpr _InnerIter&
3083 operator++()
3084 {
3085 _M_incremented = true;
3086 if constexpr (!forward_range<_Base>)
3087 if constexpr (_Pattern::size() == 0)
3088 return *this;
3089 ++_M_i_current();
3090 return *this;
3091 }
3092
3093 constexpr decltype(auto)
3094 operator++(int)
3095 {
3096 if constexpr (forward_range<_Base>)
3097 {
3098 auto __tmp = *this;
3099 ++*this;
3100 return __tmp;
3101 }
3102 else
3103 ++*this;
3104 }
3105
3106 friend constexpr bool
3107 operator==(const _InnerIter& __x, const _InnerIter& __y)
3108 requires forward_range<_Base>
3109 { return __x._M_i == __y._M_i; }
3110
3111 friend constexpr bool
3112 operator==(const _InnerIter& __x, default_sentinel_t)
3113 { return __x.__at_end(); }
3114
3115 friend constexpr decltype(auto)
3116 iter_move(const _InnerIter& __i)
3117 noexcept(noexcept(ranges::iter_move(__i._M_i_current())))
3118 { return ranges::iter_move(__i._M_i_current()); }
3119
3120 friend constexpr void
3121 iter_swap(const _InnerIter& __x, const _InnerIter& __y)
3122 noexcept(noexcept(ranges::iter_swap(__x._M_i_current(),
3123 __y._M_i_current())))
3124 requires indirectly_swappable<iterator_t<_Base>>
3125 { ranges::iter_swap(__x._M_i_current(), __y._M_i_current()); }
3126 };
3127
3128 _Pattern _M_pattern = _Pattern();
3129 // XXX: _M_current is "present only if !forward_range<V>"
3130 [[no_unique_address]]
3131 __detail::__maybe_present_t<!forward_range<_Vp>,
3132 iterator_t<_Vp>> _M_current;
3133 _Vp _M_base = _Vp();
3134
3135
3136 public:
3137 split_view() requires (default_initializable<_Vp>
3138 && default_initializable<_Pattern>
3139 && (forward_range<_Vp>
3140 || default_initializable<iterator_t<_Vp>>))
3141 = default;
3142
3143 constexpr
3144 split_view(_Vp __base, _Pattern __pattern)
3145 : _M_pattern(std::move(__pattern)), _M_base(std::move(__base))
3146 { }
3147
3148 template<input_range _Range>
3149 requires constructible_from<_Vp, views::all_t<_Range>>
3150 && constructible_from<_Pattern, single_view<range_value_t<_Range>>>
3151 constexpr
3152 split_view(_Range&& __r, range_value_t<_Range> __e)
3153 : _M_pattern(views::single(std::move(__e))),
3154 _M_base(views::all(std::forward<_Range>(__r)))
3155 { }
3156
3157 constexpr _Vp
3158 base() const& requires copy_constructible<_Vp>
3159 { return _M_base; }
3160
3161 constexpr _Vp
3162 base() &&
3163 { return std::move(_M_base); }
3164
3165 constexpr auto
3166 begin()
3167 {
3168 if constexpr (forward_range<_Vp>)
3169 {
3170 constexpr bool __simple
3171 = __detail::__simple_view<_Vp> && __detail::__simple_view<_Pattern>;
3172 return _OuterIter<__simple>{this, ranges::begin(_M_base)};
3173 }
3174 else
3175 {
3176 _M_current = ranges::begin(_M_base);
3177 return _OuterIter<false>{this};
3178 }
3179 }
3180
3181 constexpr auto
3182 begin() const requires forward_range<_Vp> && forward_range<const _Vp>
3183 {
3184 return _OuterIter<true>{this, ranges::begin(_M_base)};
3185 }
3186
3187 constexpr auto
3188 end() requires forward_range<_Vp> && common_range<_Vp>
3189 {
3190 constexpr bool __simple
3191 = __detail::__simple_view<_Vp> && __detail::__simple_view<_Pattern>;
3192 return _OuterIter<__simple>{this, ranges::end(_M_base)};
3193 }
3194
3195 constexpr auto
3196 end() const
3197 {
3198 if constexpr (forward_range<_Vp>
3199 && forward_range<const _Vp>
3200 && common_range<const _Vp>)
3201 return _OuterIter<true>{this, ranges::end(_M_base)};
3202 else
3203 return default_sentinel;
3204 }
3205 };
3206
3207 template<typename _Range, typename _Pattern>
3208 split_view(_Range&&, _Pattern&&)
3209 -> split_view<views::all_t<_Range>, views::all_t<_Pattern>>;
3210
3211 template<input_range _Range>
3212 split_view(_Range&&, range_value_t<_Range>)
3213 -> split_view<views::all_t<_Range>, single_view<range_value_t<_Range>>>;
3214
3215 namespace views
3216 {
3217 namespace __detail
3218 {
3219 template<typename _Range, typename _Pattern>
3220 concept __can_split_view
3221 = requires { split_view(std::declval<_Range>(), std::declval<_Pattern>()); };
3222 } // namespace __detail
3223
3224 struct _Split : __adaptor::_RangeAdaptor<_Split>
3225 {
3226 template<viewable_range _Range, typename _Pattern>
3227 requires __detail::__can_split_view<_Range, _Pattern>
3228 constexpr auto
3229 operator()(_Range&& __r, _Pattern&& __f) const
3230 {
3231 return split_view(std::forward<_Range>(__r), std::forward<_Pattern>(__f));
3232 }
3233
3234 using _RangeAdaptor<_Split>::operator();
3235 static constexpr int _S_arity = 2;
3236 // The pattern argument of views::split is not always simple -- it can be
3237 // a non-view range, the value category of which affects whether the call
3238 // is well-formed. But a scalar or a view pattern argument is surely
3239 // simple.
3240 template<typename _Pattern>
3241 static constexpr bool _S_has_simple_extra_args
3242 = is_scalar_v<_Pattern> || (view<_Pattern>
3243 && copy_constructible<_Pattern>);
3244 };
3245
3246 inline constexpr _Split split;
3247 } // namespace views
3248
3249 namespace views
3250 {
3251 struct _Counted
3252 {
3253 template<input_or_output_iterator _Iter>
3254 constexpr auto
3255 operator()(_Iter __i, iter_difference_t<_Iter> __n) const
3256 {
3257 if constexpr (random_access_iterator<_Iter>)
3258 return subrange(__i, __i + __n);
3259 else
3260 return subrange(counted_iterator(std::move(__i), __n),
3261 default_sentinel);
3262 }
3263 };
3264
3265 inline constexpr _Counted counted{};
3266 } // namespace views
3267
3268 template<view _Vp>
3269 requires (!common_range<_Vp>) && copyable<iterator_t<_Vp>>
3270 class common_view : public view_interface<common_view<_Vp>>
3271 {
3272 private:
3273 _Vp _M_base = _Vp();
3274
3275 public:
3276 common_view() requires default_initializable<_Vp> = default;
3277
3278 constexpr explicit
3279 common_view(_Vp __r)
3280 : _M_base(std::move(__r))
3281 { }
3282
3283 /* XXX: LWG 3280 didn't remove this constructor, but I think it should?
3284 template<viewable_range _Range>
3285 requires (!common_range<_Range>)
3286 && constructible_from<_Vp, views::all_t<_Range>>
3287 constexpr explicit
3288 common_view(_Range&& __r)
3289 : _M_base(views::all(std::forward<_Range>(__r)))
3290 { }
3291 */
3292
3293 constexpr _Vp
3294 base() const& requires copy_constructible<_Vp>
3295 { return _M_base; }
3296
3297 constexpr _Vp
3298 base() &&
3299 { return std::move(_M_base); }
3300
3301 constexpr auto
3302 begin()
3303 {
3304 if constexpr (random_access_range<_Vp> && sized_range<_Vp>)
3305 return ranges::begin(_M_base);
3306 else
3307 return common_iterator<iterator_t<_Vp>, sentinel_t<_Vp>>
3308 (ranges::begin(_M_base));
3309 }
3310
3311 constexpr auto
3312 begin() const requires range<const _Vp>
3313 {
3314 if constexpr (random_access_range<const _Vp> && sized_range<const _Vp>)
3315 return ranges::begin(_M_base);
3316 else
3317 return common_iterator<iterator_t<const _Vp>, sentinel_t<const _Vp>>
3318 (ranges::begin(_M_base));
3319 }
3320
3321 constexpr auto
3322 end()
3323 {
3324 if constexpr (random_access_range<_Vp> && sized_range<_Vp>)
3325 return ranges::begin(_M_base) + ranges::size(_M_base);
3326 else
3327 return common_iterator<iterator_t<_Vp>, sentinel_t<_Vp>>
3328 (ranges::end(_M_base));
3329 }
3330
3331 constexpr auto
3332 end() const requires range<const _Vp>
3333 {
3334 if constexpr (random_access_range<const _Vp> && sized_range<const _Vp>)
3335 return ranges::begin(_M_base) + ranges::size(_M_base);
3336 else
3337 return common_iterator<iterator_t<const _Vp>, sentinel_t<const _Vp>>
3338 (ranges::end(_M_base));
3339 }
3340
3341 constexpr auto
3342 size() requires sized_range<_Vp>
3343 { return ranges::size(_M_base); }
3344
3345 constexpr auto
3346 size() const requires sized_range<const _Vp>
3347 { return ranges::size(_M_base); }
3348 };
3349
3350 template<typename _Range>
3351 common_view(_Range&&) -> common_view<views::all_t<_Range>>;
3352
3353 template<typename _Tp>
3354 inline constexpr bool enable_borrowed_range<common_view<_Tp>>
3355 = enable_borrowed_range<_Tp>;
3356
3357 namespace views
3358 {
3359 namespace __detail
3360 {
3361 template<typename _Range>
3362 concept __already_common = common_range<_Range>
3363 && requires { views::all(std::declval<_Range>()); };
3364
3365 template<typename _Range>
3366 concept __can_common_view
3367 = requires { common_view{std::declval<_Range>()}; };
3368 } // namespace __detail
3369
3370 struct _Common : __adaptor::_RangeAdaptorClosure
3371 {
3372 template<viewable_range _Range>
3373 requires __detail::__already_common<_Range>
3374 || __detail::__can_common_view<_Range>
3375 constexpr auto
3376 operator()(_Range&& __r) const
3377 {
3378 if constexpr (__detail::__already_common<_Range>)
3379 return views::all(std::forward<_Range>(__r));
3380 else
3381 return common_view{std::forward<_Range>(__r)};
3382 }
3383
3384 static constexpr bool _S_has_simple_call_op = true;
3385 };
3386
3387 inline constexpr _Common common;
3388 } // namespace views
3389
3390 template<view _Vp>
3391 requires bidirectional_range<_Vp>
3392 class reverse_view : public view_interface<reverse_view<_Vp>>
3393 {
3394 private:
3395 static constexpr bool _S_needs_cached_begin
3396 = !common_range<_Vp> && !random_access_range<_Vp>;
3397
3398 [[no_unique_address]]
3399 __detail::__maybe_present_t<_S_needs_cached_begin,
3400 __detail::_CachedPosition<_Vp>>
3401 _M_cached_begin;
3402 _Vp _M_base = _Vp();
3403
3404 public:
3405 reverse_view() requires default_initializable<_Vp> = default;
3406
3407 constexpr explicit
3408 reverse_view(_Vp __r)
3409 : _M_base(std::move(__r))
3410 { }
3411
3412 constexpr _Vp
3413 base() const& requires copy_constructible<_Vp>
3414 { return _M_base; }
3415
3416 constexpr _Vp
3417 base() &&
3418 { return std::move(_M_base); }
3419
3420 constexpr reverse_iterator<iterator_t<_Vp>>
3421 begin()
3422 {
3423 if constexpr (_S_needs_cached_begin)
3424 if (_M_cached_begin._M_has_value())
3425 return std::make_reverse_iterator(_M_cached_begin._M_get(_M_base));
3426
3427 auto __it = ranges::next(ranges::begin(_M_base), ranges::end(_M_base));
3428 if constexpr (_S_needs_cached_begin)
3429 _M_cached_begin._M_set(_M_base, __it);
3430 return std::make_reverse_iterator(std::move(__it));
3431 }
3432
3433 constexpr auto
3434 begin() requires common_range<_Vp>
3435 { return std::make_reverse_iterator(ranges::end(_M_base)); }
3436
3437 constexpr auto
3438 begin() const requires common_range<const _Vp>
3439 { return std::make_reverse_iterator(ranges::end(_M_base)); }
3440
3441 constexpr reverse_iterator<iterator_t<_Vp>>
3442 end()
3443 { return std::make_reverse_iterator(ranges::begin(_M_base)); }
3444
3445 constexpr auto
3446 end() const requires common_range<const _Vp>
3447 { return std::make_reverse_iterator(ranges::begin(_M_base)); }
3448
3449 constexpr auto
3450 size() requires sized_range<_Vp>
3451 { return ranges::size(_M_base); }
3452
3453 constexpr auto
3454 size() const requires sized_range<const _Vp>
3455 { return ranges::size(_M_base); }
3456 };
3457
3458 template<typename _Range>
3459 reverse_view(_Range&&) -> reverse_view<views::all_t<_Range>>;
3460
3461 template<typename _Tp>
3462 inline constexpr bool enable_borrowed_range<reverse_view<_Tp>>
3463 = enable_borrowed_range<_Tp>;
3464
3465 namespace views
3466 {
3467 namespace __detail
3468 {
3469 template<typename>
3470 inline constexpr bool __is_reversible_subrange = false;
3471
3472 template<typename _Iter, subrange_kind _Kind>
3473 inline constexpr bool
3474 __is_reversible_subrange<subrange<reverse_iterator<_Iter>,
3475 reverse_iterator<_Iter>,
3476 _Kind>> = true;
3477
3478 template<typename>
3479 inline constexpr bool __is_reverse_view = false;
3480
3481 template<typename _Vp>
3482 inline constexpr bool __is_reverse_view<reverse_view<_Vp>> = true;
3483
3484 template<typename _Range>
3485 concept __can_reverse_view
3486 = requires { reverse_view{std::declval<_Range>()}; };
3487 } // namespace __detail
3488
3489 struct _Reverse : __adaptor::_RangeAdaptorClosure
3490 {
3491 template<viewable_range _Range>
3492 requires __detail::__is_reverse_view<remove_cvref_t<_Range>>
3493 || __detail::__is_reversible_subrange<remove_cvref_t<_Range>>
3494 || __detail::__can_reverse_view<_Range>
3495 constexpr auto
3496 operator()(_Range&& __r) const
3497 {
3498 using _Tp = remove_cvref_t<_Range>;
3499 if constexpr (__detail::__is_reverse_view<_Tp>)
3500 return std::forward<_Range>(__r).base();
3501 else if constexpr (__detail::__is_reversible_subrange<_Tp>)
3502 {
3503 using _Iter = decltype(ranges::begin(__r).base());
3504 if constexpr (sized_range<_Tp>)
3505 return subrange<_Iter, _Iter, subrange_kind::sized>
3506 {__r.end().base(), __r.begin().base(), __r.size()};
3507 else
3508 return subrange<_Iter, _Iter, subrange_kind::unsized>
3509 {__r.end().base(), __r.begin().base()};
3510 }
3511 else
3512 return reverse_view{std::forward<_Range>(__r)};
3513 }
3514
3515 static constexpr bool _S_has_simple_call_op = true;
3516 };
3517
3518 inline constexpr _Reverse reverse;
3519 } // namespace views
3520
3521 namespace __detail
3522 {
3523 template<typename _Tp, size_t _Nm>
3524 concept __has_tuple_element = requires(_Tp __t)
3525 {
3526 typename tuple_size<_Tp>::type;
3527 requires _Nm < tuple_size_v<_Tp>;
3528 typename tuple_element_t<_Nm, _Tp>;
3529 { std::get<_Nm>(__t) }
3530 -> convertible_to<const tuple_element_t<_Nm, _Tp>&>;
3531 };
3532
3533 template<typename _Tp, size_t _Nm>
3534 concept __returnable_element
3535 = is_reference_v<_Tp> || move_constructible<tuple_element_t<_Nm, _Tp>>;
3536 }
3537
3538 template<input_range _Vp, size_t _Nm>
3539 requires view<_Vp>
3540 && __detail::__has_tuple_element<range_value_t<_Vp>, _Nm>
3541 && __detail::__has_tuple_element<remove_reference_t<range_reference_t<_Vp>>,
3542 _Nm>
3543 && __detail::__returnable_element<range_reference_t<_Vp>, _Nm>
3544 class elements_view : public view_interface<elements_view<_Vp, _Nm>>
3545 {
3546 public:
3547 elements_view() requires default_initializable<_Vp> = default;
3548
3549 constexpr explicit
3550 elements_view(_Vp base)
3551 : _M_base(std::move(base))
3552 { }
3553
3554 constexpr _Vp
3555 base() const& requires copy_constructible<_Vp>
3556 { return _M_base; }
3557
3558 constexpr _Vp
3559 base() &&
3560 { return std::move(_M_base); }
3561
3562 constexpr auto
3563 begin() requires (!__detail::__simple_view<_Vp>)
3564 { return _Iterator<false>(ranges::begin(_M_base)); }
3565
3566 constexpr auto
3567 begin() const requires range<const _Vp>
3568 { return _Iterator<true>(ranges::begin(_M_base)); }
3569
3570 constexpr auto
3571 end() requires (!__detail::__simple_view<_Vp> && !common_range<_Vp>)
3572 { return _Sentinel<false>{ranges::end(_M_base)}; }
3573
3574 constexpr auto
3575 end() requires (!__detail::__simple_view<_Vp> && common_range<_Vp>)
3576 { return _Iterator<false>{ranges::end(_M_base)}; }
3577
3578 constexpr auto
3579 end() const requires range<const _Vp>
3580 { return _Sentinel<true>{ranges::end(_M_base)}; }
3581
3582 constexpr auto
3583 end() const requires common_range<const _Vp>
3584 { return _Iterator<true>{ranges::end(_M_base)}; }
3585
3586 constexpr auto
3587 size() requires sized_range<_Vp>
3588 { return ranges::size(_M_base); }
3589
3590 constexpr auto
3591 size() const requires sized_range<const _Vp>
3592 { return ranges::size(_M_base); }
3593
3594 private:
3595 template<bool _Const>
3596 using _Base = __detail::__maybe_const_t<_Const, _Vp>;
3597
3598 template<bool _Const>
3599 struct __iter_cat
3600 { };
3601
3602 template<bool _Const>
3603 requires forward_range<_Base<_Const>>
3604 struct __iter_cat<_Const>
3605 {
3606 private:
3607 static auto _S_iter_cat()
3608 {
3609 using _Base = elements_view::_Base<_Const>;
3610 using _Cat = typename iterator_traits<iterator_t<_Base>>::iterator_category;
3611 using _Res = decltype((std::get<_Nm>(*std::declval<iterator_t<_Base>>())));
3612 if constexpr (!is_lvalue_reference_v<_Res>)
3613 return input_iterator_tag{};
3614 else if constexpr (derived_from<_Cat, random_access_iterator_tag>)
3615 return random_access_iterator_tag{};
3616 else
3617 return _Cat{};
3618 }
3619 public:
3620 using iterator_category = decltype(_S_iter_cat());
3621 };
3622
3623 template<bool _Const>
3624 struct _Sentinel;
3625
3626 template<bool _Const>
3627 struct _Iterator : __iter_cat<_Const>
3628 {
3629 private:
3630 using _Base = elements_view::_Base<_Const>;
3631
3632 iterator_t<_Base> _M_current = iterator_t<_Base>();
3633
3634 static constexpr decltype(auto)
3635 _S_get_element(const iterator_t<_Base>& __i)
3636 {
3637 if constexpr (is_reference_v<range_reference_t<_Base>>)
3638 return std::get<_Nm>(*__i);
3639 else
3640 {
3641 using _Et = remove_cv_t<tuple_element_t<_Nm, range_reference_t<_Base>>>;
3642 return static_cast<_Et>(std::get<_Nm>(*__i));
3643 }
3644 }
3645
3646 static auto
3647 _S_iter_concept()
3648 {
3649 if constexpr (random_access_range<_Base>)
3650 return random_access_iterator_tag{};
3651 else if constexpr (bidirectional_range<_Base>)
3652 return bidirectional_iterator_tag{};
3653 else if constexpr (forward_range<_Base>)
3654 return forward_iterator_tag{};
3655 else
3656 return input_iterator_tag{};
3657 }
3658
3659 friend _Iterator<!_Const>;
3660
3661 public:
3662 using iterator_concept = decltype(_S_iter_concept());
3663 // iterator_category defined in elements_view::__iter_cat
3664 using value_type
3665 = remove_cvref_t<tuple_element_t<_Nm, range_value_t<_Base>>>;
3666 using difference_type = range_difference_t<_Base>;
3667
3668 _Iterator() requires default_initializable<iterator_t<_Base>> = default;
3669
3670 constexpr explicit
3671 _Iterator(iterator_t<_Base> current)
3672 : _M_current(std::move(current))
3673 { }
3674
3675 constexpr
3676 _Iterator(_Iterator<!_Const> i)
3677 requires _Const && convertible_to<iterator_t<_Vp>, iterator_t<_Base>>
3678 : _M_current(std::move(i._M_current))
3679 { }
3680
3681 constexpr const iterator_t<_Base>&
3682 base() const& noexcept
3683 { return _M_current; }
3684
3685 constexpr iterator_t<_Base>
3686 base() &&
3687 { return std::move(_M_current); }
3688
3689 constexpr decltype(auto)
3690 operator*() const
3691 { return _S_get_element(_M_current); }
3692
3693 constexpr _Iterator&
3694 operator++()
3695 {
3696 ++_M_current;
3697 return *this;
3698 }
3699
3700 constexpr void
3701 operator++(int)
3702 { ++_M_current; }
3703
3704 constexpr _Iterator
3705 operator++(int) requires forward_range<_Base>
3706 {
3707 auto __tmp = *this;
3708 ++_M_current;
3709 return __tmp;
3710 }
3711
3712 constexpr _Iterator&
3713 operator--() requires bidirectional_range<_Base>
3714 {
3715 --_M_current;
3716 return *this;
3717 }
3718
3719 constexpr _Iterator
3720 operator--(int) requires bidirectional_range<_Base>
3721 {
3722 auto __tmp = *this;
3723 --_M_current;
3724 return __tmp;
3725 }
3726
3727 constexpr _Iterator&
3728 operator+=(difference_type __n)
3729 requires random_access_range<_Base>
3730 {
3731 _M_current += __n;
3732 return *this;
3733 }
3734
3735 constexpr _Iterator&
3736 operator-=(difference_type __n)
3737 requires random_access_range<_Base>
3738 {
3739 _M_current -= __n;
3740 return *this;
3741 }
3742
3743 constexpr decltype(auto)
3744 operator[](difference_type __n) const
3745 requires random_access_range<_Base>
3746 { return _S_get_element(_M_current + __n); }
3747
3748 friend constexpr bool
3749 operator==(const _Iterator& __x, const _Iterator& __y)
3750 requires equality_comparable<iterator_t<_Base>>
3751 { return __x._M_current == __y._M_current; }
3752
3753 friend constexpr bool
3754 operator<(const _Iterator& __x, const _Iterator& __y)
3755 requires random_access_range<_Base>
3756 { return __x._M_current < __y._M_current; }
3757
3758 friend constexpr bool
3759 operator>(const _Iterator& __x, const _Iterator& __y)
3760 requires random_access_range<_Base>
3761 { return __y._M_current < __x._M_current; }
3762
3763 friend constexpr bool
3764 operator<=(const _Iterator& __x, const _Iterator& __y)
3765 requires random_access_range<_Base>
3766 { return !(__y._M_current > __x._M_current); }
3767
3768 friend constexpr bool
3769 operator>=(const _Iterator& __x, const _Iterator& __y)
3770 requires random_access_range<_Base>
3771 { return !(__x._M_current > __y._M_current); }
3772
3773#ifdef __cpp_lib_three_way_comparison
3774 friend constexpr auto
3775 operator<=>(const _Iterator& __x, const _Iterator& __y)
3776 requires random_access_range<_Base>
3777 && three_way_comparable<iterator_t<_Base>>
3778 { return __x._M_current <=> __y._M_current; }
3779#endif
3780
3781 friend constexpr _Iterator
3782 operator+(const _Iterator& __x, difference_type __y)
3783 requires random_access_range<_Base>
3784 { return _Iterator{__x} += __y; }
3785
3786 friend constexpr _Iterator
3787 operator+(difference_type __x, const _Iterator& __y)
3788 requires random_access_range<_Base>
3789 { return __y + __x; }
3790
3791 friend constexpr _Iterator
3792 operator-(const _Iterator& __x, difference_type __y)
3793 requires random_access_range<_Base>
3794 { return _Iterator{__x} -= __y; }
3795
3796 // _GLIBCXX_RESOLVE_LIB_DEFECTS
3797 // 3483. transform_view::iterator's difference is overconstrained
3798 friend constexpr difference_type
3799 operator-(const _Iterator& __x, const _Iterator& __y)
3800 requires sized_sentinel_for<iterator_t<_Base>, iterator_t<_Base>>
3801 { return __x._M_current - __y._M_current; }
3802
3803 template <bool> friend struct _Sentinel;
3804 };
3805
3806 template<bool _Const>
3807 struct _Sentinel
3808 {
3809 private:
3810 template<bool _Const2>
3811 constexpr bool
3812 _M_equal(const _Iterator<_Const2>& __x) const
3813 { return __x._M_current == _M_end; }
3814
3815 template<bool _Const2>
3816 constexpr auto
3817 _M_distance_from(const _Iterator<_Const2>& __i) const
3818 { return _M_end - __i._M_current; }
3819
3820 using _Base = elements_view::_Base<_Const>;
3821 sentinel_t<_Base> _M_end = sentinel_t<_Base>();
3822
3823 public:
3824 _Sentinel() = default;
3825
3826 constexpr explicit
3827 _Sentinel(sentinel_t<_Base> __end)
3828 : _M_end(std::move(__end))
3829 { }
3830
3831 constexpr
3832 _Sentinel(_Sentinel<!_Const> __other)
3833 requires _Const
3834 && convertible_to<sentinel_t<_Vp>, sentinel_t<_Base>>
3835 : _M_end(std::move(__other._M_end))
3836 { }
3837
3838 constexpr sentinel_t<_Base>
3839 base() const
3840 { return _M_end; }
3841
3842 template<bool _Const2>
3843 requires sentinel_for<sentinel_t<_Base>,
3844 iterator_t<__detail::__maybe_const_t<_Const2, _Vp>>>
3845 friend constexpr bool
3846 operator==(const _Iterator<_Const2>& __x, const _Sentinel& __y)
3847 { return __y._M_equal(__x); }
3848
3849 template<bool _Const2,
3850 typename _Base2 = __detail::__maybe_const_t<_Const2, _Vp>>
3851 requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<_Base2>>
3852 friend constexpr range_difference_t<_Base2>
3853 operator-(const _Iterator<_Const2>& __x, const _Sentinel& __y)
3854 { return -__y._M_distance_from(__x); }
3855
3856 template<bool _Const2,
3857 typename _Base2 = __detail::__maybe_const_t<_Const2, _Vp>>
3858 requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<_Base2>>
3859 friend constexpr range_difference_t<_Base2>
3860 operator-(const _Sentinel& __x, const _Iterator<_Const2>& __y)
3861 { return __x._M_distance_from(__y); }
3862
3863 friend _Sentinel<!_Const>;
3864 };
3865
3866 _Vp _M_base = _Vp();
3867 };
3868
3869 template<typename _Tp, size_t _Nm>
3870 inline constexpr bool enable_borrowed_range<elements_view<_Tp, _Nm>>
3871 = enable_borrowed_range<_Tp>;
3872
3873 template<typename _Range>
3874 using keys_view = elements_view<views::all_t<_Range>, 0>;
3875
3876 template<typename _Range>
3877 using values_view = elements_view<views::all_t<_Range>, 1>;
3878
3879 namespace views
3880 {
3881 namespace __detail
3882 {
3883 template<size_t _Nm, typename _Range>
3884 concept __can_elements_view
3885 = requires { elements_view<all_t<_Range>, _Nm>{std::declval<_Range>()}; };
3886 } // namespace __detail
3887
3888 template<size_t _Nm>
3889 struct _Elements : __adaptor::_RangeAdaptorClosure
3890 {
3891 template<viewable_range _Range>
3892 requires __detail::__can_elements_view<_Nm, _Range>
3893 constexpr auto
3894 operator()(_Range&& __r) const
3895 {
3896 return elements_view<all_t<_Range>, _Nm>{std::forward<_Range>(__r)};
3897 }
3898
3899 static constexpr bool _S_has_simple_call_op = true;
3900 };
3901
3902 template<size_t _Nm>
3903 inline constexpr _Elements<_Nm> elements;
3904 inline constexpr auto keys = elements<0>;
3905 inline constexpr auto values = elements<1>;
3906 } // namespace views
3907
3908} // namespace ranges
3909
3910 namespace views = ranges::views;
3911
3912_GLIBCXX_END_NAMESPACE_VERSION
3913} // namespace
3914#endif // library concepts
3915#endif // C++2a
3916#endif /* _GLIBCXX_RANGES */