1 // <ranges> -*- C++ -*-
3 // Copyright (C) 2019-2020 Free Software Foundation, Inc.
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)
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.
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.
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/>.
25 /** @file include/ranges
26 * This is a Standard C++ Library header.
30 #ifndef _GLIBCXX_RANGES
31 #define _GLIBCXX_RANGES 1
33 #if __cplusplus > 201703L
35 #pragma GCC system_header
39 #if __cpp_lib_concepts
41 #include <bits/refwrap.h>
43 #include <initializer_list>
49 * @defgroup ranges Ranges
51 * Components for dealing with ranges of elements.
54 namespace std _GLIBCXX_VISIBILITY(default)
56 _GLIBCXX_BEGIN_NAMESPACE_VERSION
59 // [range.range] The range concept.
60 // [range.sized] The sized_range concept.
61 // Defined in <bits/range_access.h>
63 // [range.refinements]
64 // Defined in <bits/range_access.h>
68 template<typename _Tp>
69 inline constexpr bool enable_view = derived_from<_Tp, view_base>;
71 template<typename _Tp>
73 = range<_Tp> && movable<_Tp> && default_initializable<_Tp>
76 /// A range which can be safely converted to a view.
77 template<typename _Tp>
78 concept viewable_range = range<_Tp>
79 && (borrowed_range<_Tp> || view<remove_cvref_t<_Tp>>);
83 template<typename _Range>
84 concept __simple_view = view<_Range> && range<const _Range>
85 && same_as<iterator_t<_Range>, iterator_t<const _Range>>
86 && same_as<sentinel_t<_Range>, sentinel_t<const _Range>>;
88 template<typename _It>
89 concept __has_arrow = input_iterator<_It>
90 && (is_pointer_v<_It> || requires(_It __it) { __it.operator->(); });
92 template<typename _Tp, typename _Up>
94 = !same_as<remove_cvref_t<_Tp>, remove_cvref_t<_Up>>;
95 } // namespace __detail
97 template<typename _Derived>
98 requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>>
99 class view_interface : public view_base
102 constexpr _Derived& _M_derived() noexcept
104 static_assert(derived_from<_Derived, view_interface<_Derived>>);
105 static_assert(view<_Derived>);
106 return static_cast<_Derived&>(*this);
109 constexpr const _Derived& _M_derived() const noexcept
111 static_assert(derived_from<_Derived, view_interface<_Derived>>);
112 static_assert(view<_Derived>);
113 return static_cast<const _Derived&>(*this);
118 empty() requires forward_range<_Derived>
119 { return ranges::begin(_M_derived()) == ranges::end(_M_derived()); }
122 empty() const requires forward_range<const _Derived>
123 { return ranges::begin(_M_derived()) == ranges::end(_M_derived()); }
126 operator bool() requires requires { ranges::empty(_M_derived()); }
127 { return !ranges::empty(_M_derived()); }
130 operator bool() const requires requires { ranges::empty(_M_derived()); }
131 { return !ranges::empty(_M_derived()); }
134 data() requires contiguous_iterator<iterator_t<_Derived>>
135 { return to_address(ranges::begin(_M_derived())); }
139 requires range<const _Derived>
140 && contiguous_iterator<iterator_t<const _Derived>>
141 { return to_address(ranges::begin(_M_derived())); }
145 requires forward_range<_Derived>
146 && sized_sentinel_for<sentinel_t<_Derived>, iterator_t<_Derived>>
147 { return ranges::end(_M_derived()) - ranges::begin(_M_derived()); }
151 requires forward_range<const _Derived>
152 && sized_sentinel_for<sentinel_t<const _Derived>,
153 iterator_t<const _Derived>>
154 { return ranges::end(_M_derived()) - ranges::begin(_M_derived()); }
156 constexpr decltype(auto)
157 front() requires forward_range<_Derived>
159 __glibcxx_assert(!empty());
160 return *ranges::begin(_M_derived());
163 constexpr decltype(auto)
164 front() const requires forward_range<const _Derived>
166 __glibcxx_assert(!empty());
167 return *ranges::begin(_M_derived());
170 constexpr decltype(auto)
172 requires bidirectional_range<_Derived> && common_range<_Derived>
174 __glibcxx_assert(!empty());
175 return *ranges::prev(ranges::end(_M_derived()));
178 constexpr decltype(auto)
180 requires bidirectional_range<const _Derived>
181 && common_range<const _Derived>
183 __glibcxx_assert(!empty());
184 return *ranges::prev(ranges::end(_M_derived()));
187 template<random_access_range _Range = _Derived>
188 constexpr decltype(auto)
189 operator[](range_difference_t<_Range> __n)
190 { return ranges::begin(_M_derived())[__n]; }
192 template<random_access_range _Range = const _Derived>
193 constexpr decltype(auto)
194 operator[](range_difference_t<_Range> __n) const
195 { return ranges::begin(_M_derived())[__n]; }
200 template<class _From, class _To>
201 concept __convertible_to_non_slicing = convertible_to<_From, _To>
202 && !(is_pointer_v<decay_t<_From>> && is_pointer_v<decay_t<_To>>
203 && __not_same_as<remove_pointer_t<decay_t<_From>>,
204 remove_pointer_t<decay_t<_To>>>);
206 template<typename _Tp>
208 = !is_reference_v<_Tp> && requires(_Tp __t)
210 typename tuple_size<_Tp>::type;
211 requires derived_from<tuple_size<_Tp>, integral_constant<size_t, 2>>;
212 typename tuple_element_t<0, remove_const_t<_Tp>>;
213 typename tuple_element_t<1, remove_const_t<_Tp>>;
214 { get<0>(__t) } -> convertible_to<const tuple_element_t<0, _Tp>&>;
215 { get<1>(__t) } -> convertible_to<const tuple_element_t<1, _Tp>&>;
218 template<typename _Tp, typename _Up, typename _Vp>
219 concept __pair_like_convertible_from
220 = !range<_Tp> && __pair_like<_Tp>
221 && constructible_from<_Tp, _Up, _Vp>
222 && __convertible_to_non_slicing<_Up, tuple_element_t<0, _Tp>>
223 && convertible_to<_Vp, tuple_element_t<1, _Tp>>;
225 template<typename _Tp>
226 concept __iterator_sentinel_pair
227 = !range<_Tp> && __pair_like<_Tp>
228 && sentinel_for<tuple_element_t<1, _Tp>, tuple_element_t<0, _Tp>>;
230 } // namespace __detail
232 enum class subrange_kind : bool { unsized, sized };
234 template<input_or_output_iterator _It, sentinel_for<_It> _Sent = _It,
235 subrange_kind _Kind = sized_sentinel_for<_Sent, _It>
236 ? subrange_kind::sized : subrange_kind::unsized>
237 requires (_Kind == subrange_kind::sized || !sized_sentinel_for<_Sent, _It>)
238 class subrange : public view_interface<subrange<_It, _Sent, _Kind>>
241 // XXX: gcc complains when using constexpr here
242 static const bool _S_store_size
243 = _Kind == subrange_kind::sized && !sized_sentinel_for<_Sent, _It>;
245 _It _M_begin = _It();
246 _Sent _M_end = _Sent();
248 template<typename, bool = _S_store_size>
252 template<typename _Tp>
253 struct _Size<_Tp, true>
254 { __detail::__make_unsigned_like_t<_Tp> _M_size; };
256 [[no_unique_address]] _Size<iter_difference_t<_It>> _M_size = {};
259 subrange() = default;
262 subrange(__detail::__convertible_to_non_slicing<_It> auto __i, _Sent __s)
263 requires (!_S_store_size)
264 : _M_begin(std::move(__i)), _M_end(__s)
268 subrange(__detail::__convertible_to_non_slicing<_It> auto __i, _Sent __s,
269 __detail::__make_unsigned_like_t<iter_difference_t<_It>> __n)
270 requires (_Kind == subrange_kind::sized)
271 : _M_begin(std::move(__i)), _M_end(__s)
273 using __detail::__to_unsigned_like;
274 __glibcxx_assert(__n == __to_unsigned_like(ranges::distance(__i, __s)));
275 if constexpr (_S_store_size)
276 _M_size._M_size = __n;
279 template<__detail::__not_same_as<subrange> _Rng>
280 requires borrowed_range<_Rng>
281 && __detail::__convertible_to_non_slicing<iterator_t<_Rng>, _It>
282 && convertible_to<sentinel_t<_Rng>, _Sent>
284 subrange(_Rng&& __r) requires (!_S_store_size || sized_range<_Rng>)
285 : subrange{ranges::begin(__r), ranges::end(__r)}
287 if constexpr (_S_store_size)
288 _M_size._M_size = ranges::size(__r);
291 template<borrowed_range _Rng>
292 requires __detail::__convertible_to_non_slicing<iterator_t<_Rng>, _It>
293 && convertible_to<sentinel_t<_Rng>, _Sent>
296 __detail::__make_unsigned_like_t<iter_difference_t<_It>> __n)
297 requires (_Kind == subrange_kind::sized)
298 : subrange{ranges::begin(__r), ranges::end(__r), __n}
301 template<__detail::__not_same_as<subrange> _PairLike>
302 requires __detail::__pair_like_convertible_from<_PairLike, const _It&,
305 operator _PairLike() const
306 { return _PairLike(_M_begin, _M_end); }
309 begin() const requires copyable<_It>
312 [[nodiscard]] constexpr _It
313 begin() requires (!copyable<_It>)
314 { return std::move(_M_begin); }
316 constexpr _Sent end() const { return _M_end; }
318 constexpr bool empty() const { return _M_begin == _M_end; }
320 constexpr __detail::__make_unsigned_like_t<iter_difference_t<_It>>
321 size() const requires (_Kind == subrange_kind::sized)
323 if constexpr (_S_store_size)
324 return _M_size._M_size;
326 return __detail::__to_unsigned_like(_M_end - _M_begin);
329 [[nodiscard]] constexpr subrange
330 next(iter_difference_t<_It> __n = 1) const &
331 requires forward_iterator<_It>
338 [[nodiscard]] constexpr subrange
339 next(iter_difference_t<_It> __n = 1) &&
342 return std::move(*this);
345 [[nodiscard]] constexpr subrange
346 prev(iter_difference_t<_It> __n = 1) const
347 requires bidirectional_iterator<_It>
350 __tmp.advance(--__n);
355 advance(iter_difference_t<_It> __n)
357 if constexpr (_S_store_size)
359 auto __d = __n - ranges::advance(_M_begin, __n, _M_end);
361 _M_size._M_size -= __detail::__to_unsigned_like(__d);
363 _M_size._M_size += __detail::__to_unsigned_like(-__d);
366 ranges::advance(_M_begin, __n, _M_end);
371 template<input_or_output_iterator _It, sentinel_for<_It> _Sent>
372 subrange(_It, _Sent) -> subrange<_It, _Sent>;
374 template<input_or_output_iterator _It, sentinel_for<_It> _Sent>
376 __detail::__make_unsigned_like_t<iter_difference_t<_It>>)
377 -> subrange<_It, _Sent, subrange_kind::sized>;
379 template<__detail::__iterator_sentinel_pair _Pr>
381 -> subrange<tuple_element_t<0, _Pr>, tuple_element_t<1, _Pr>>;
383 template<__detail::__iterator_sentinel_pair _Pr>
384 subrange(_Pr, __detail::__make_unsigned_like_t<iter_difference_t<
385 tuple_element_t<0, _Pr>>>)
386 -> subrange<tuple_element_t<0, _Pr>, tuple_element_t<1, _Pr>,
387 subrange_kind::sized>;
389 template<borrowed_range _Rng>
391 -> subrange<iterator_t<_Rng>, sentinel_t<_Rng>,
393 || sized_sentinel_for<sentinel_t<_Rng>, iterator_t<_Rng>>)
394 ? subrange_kind::sized : subrange_kind::unsized>;
396 template<borrowed_range _Rng>
398 __detail::__make_unsigned_like_t<range_difference_t<_Rng>>)
399 -> subrange<iterator_t<_Rng>, sentinel_t<_Rng>, subrange_kind::sized>;
401 template<size_t _Num, class _It, class _Sent, subrange_kind _Kind>
404 get(const subrange<_It, _Sent, _Kind>& __r)
406 if constexpr (_Num == 0)
412 template<size_t _Num, class _It, class _Sent, subrange_kind _Kind>
415 get(subrange<_It, _Sent, _Kind>&& __r)
417 if constexpr (_Num == 0)
423 template<input_or_output_iterator _It, sentinel_for<_It> _Sent,
425 inline constexpr bool
426 enable_borrowed_range<subrange<_It, _Sent, _Kind>> = true;
428 } // namespace ranges
434 /// Type returned by algorithms instead of a dangling iterator or subrange.
437 constexpr dangling() noexcept = default;
438 template<typename... _Args>
439 constexpr dangling(_Args&&...) noexcept { }
442 template<range _Range>
443 using borrowed_iterator_t = conditional_t<borrowed_range<_Range>,
447 template<range _Range>
448 using borrowed_subrange_t = conditional_t<borrowed_range<_Range>,
449 subrange<iterator_t<_Range>>,
452 template<typename _Tp> requires is_object_v<_Tp>
454 : public view_interface<empty_view<_Tp>>
457 static constexpr _Tp* begin() noexcept { return nullptr; }
458 static constexpr _Tp* end() noexcept { return nullptr; }
459 static constexpr _Tp* data() noexcept { return nullptr; }
460 static constexpr size_t size() noexcept { return 0; }
461 static constexpr bool empty() noexcept { return true; }
464 template<typename _Tp>
465 inline constexpr bool enable_borrowed_range<empty_view<_Tp>> = true;
469 template<copy_constructible _Tp> requires is_object_v<_Tp>
470 struct __box : std::optional<_Tp>
472 using std::optional<_Tp>::optional;
476 noexcept(is_nothrow_default_constructible_v<_Tp>)
477 requires default_initializable<_Tp>
478 : std::optional<_Tp>{std::in_place}
481 __box(const __box&) = default;
482 __box(__box&&) = default;
484 using std::optional<_Tp>::operator=;
487 operator=(const __box& __that)
488 noexcept(is_nothrow_copy_constructible_v<_Tp>)
489 requires (!assignable_from<_Tp&, const _Tp&>)
492 this->emplace(*__that);
499 operator=(__box&& __that)
500 noexcept(is_nothrow_move_constructible_v<_Tp>)
501 requires (!assignable_from<_Tp&, _Tp>)
504 this->emplace(std::move(*__that));
511 } // namespace __detail
513 /// A view that contains exactly one element.
514 template<copy_constructible _Tp> requires is_object_v<_Tp>
515 class single_view : public view_interface<single_view<_Tp>>
518 single_view() = default;
521 single_view(const _Tp& __t)
526 single_view(_Tp&& __t)
527 : _M_value(std::move(__t))
530 template<typename... _Args>
531 requires constructible_from<_Tp, _Args...>
533 single_view(in_place_t, _Args&&... __args)
534 : _M_value{in_place, std::forward<_Args>(__args)...}
542 begin() const noexcept
547 { return data() + 1; }
551 { return data() + 1; }
553 static constexpr size_t
559 { return _M_value.operator->(); }
562 data() const noexcept
563 { return _M_value.operator->(); }
566 __detail::__box<_Tp> _M_value;
571 template<typename _Wp>
572 constexpr auto __to_signed_like(_Wp __w) noexcept
574 if constexpr (!integral<_Wp>)
575 return iter_difference_t<_Wp>();
576 else if constexpr (sizeof(iter_difference_t<_Wp>) > sizeof(_Wp))
577 return iter_difference_t<_Wp>(__w);
578 else if constexpr (sizeof(ptrdiff_t) > sizeof(_Wp))
579 return ptrdiff_t(__w);
580 else if constexpr (sizeof(long long) > sizeof(_Wp))
581 return (long long)(__w);
582 #ifdef __SIZEOF_INT128__
583 else if constexpr (__SIZEOF_INT128__ > sizeof(_Wp))
584 return __int128(__w);
587 return __max_diff_type(__w);
590 template<typename _Wp>
591 using __iota_diff_t = decltype(__to_signed_like(std::declval<_Wp>()));
593 template<typename _It>
594 concept __decrementable = incrementable<_It>
597 { --__i } -> same_as<_It&>;
598 { __i-- } -> same_as<_It>;
601 template<typename _It>
602 concept __advanceable = __decrementable<_It> && totally_ordered<_It>
603 && requires( _It __i, const _It __j, const __iota_diff_t<_It> __n)
605 { __i += __n } -> same_as<_It&>;
606 { __i -= __n } -> same_as<_It&>;
610 { __j - __j } -> convertible_to<__iota_diff_t<_It>>;
613 } // namespace __detail
615 template<weakly_incrementable _Winc,
616 semiregular _Bound = unreachable_sentinel_t>
617 requires std::__detail::__weakly_eq_cmp_with<_Winc, _Bound>
618 && semiregular<_Winc>
619 class iota_view : public view_interface<iota_view<_Winc, _Bound>>
630 using namespace __detail;
631 if constexpr (__advanceable<_Winc>)
632 return random_access_iterator_tag{};
633 else if constexpr (__decrementable<_Winc>)
634 return bidirectional_iterator_tag{};
635 else if constexpr (incrementable<_Winc>)
636 return forward_iterator_tag{};
638 return input_iterator_tag{};
642 using iterator_category = decltype(_S_iter_cat());
643 using value_type = _Winc;
644 using difference_type = __detail::__iota_diff_t<_Winc>;
646 _Iterator() = default;
649 _Iterator(_Winc __value)
650 : _M_value(__value) { }
653 operator*() const noexcept(is_nothrow_copy_constructible_v<_Winc>)
668 operator++(int) requires incrementable<_Winc>
676 operator--() requires __detail::__decrementable<_Winc>
683 operator--(int) requires __detail::__decrementable<_Winc>
691 operator+=(difference_type __n) requires __detail::__advanceable<_Winc>
693 using __detail::__is_integer_like;
694 using __detail::__is_signed_integer_like;
695 if constexpr (__is_integer_like<_Winc>
696 && !__is_signed_integer_like<_Winc>)
698 if (__n >= difference_type(0))
699 _M_value += static_cast<_Winc>(__n);
701 _M_value -= static_cast<_Winc>(-__n);
709 operator-=(difference_type __n) requires __detail::__advanceable<_Winc>
711 using __detail::__is_integer_like;
712 using __detail::__is_signed_integer_like;
713 if constexpr (__is_integer_like<_Winc>
714 && !__is_signed_integer_like<_Winc>)
716 if (__n >= difference_type(0))
717 _M_value -= static_cast<_Winc>(__n);
719 _M_value += static_cast<_Winc>(-__n);
727 operator[](difference_type __n) const
728 requires __detail::__advanceable<_Winc>
729 { return _Winc(_M_value + __n); }
731 friend constexpr bool
732 operator==(const _Iterator& __x, const _Iterator& __y)
733 requires equality_comparable<_Winc>
734 { return __x._M_value == __y._M_value; }
736 friend constexpr bool
737 operator<(const _Iterator& __x, const _Iterator& __y)
738 requires totally_ordered<_Winc>
739 { return __x._M_value < __y._M_value; }
741 friend constexpr bool
742 operator>(const _Iterator& __x, const _Iterator& __y)
743 requires totally_ordered<_Winc>
744 { return __y < __x; }
746 friend constexpr bool
747 operator<=(const _Iterator& __x, const _Iterator& __y)
748 requires totally_ordered<_Winc>
749 { return !(__y < __x); }
751 friend constexpr bool
752 operator>=(const _Iterator& __x, const _Iterator& __y)
753 requires totally_ordered<_Winc>
754 { return !(__x < __y); }
756 #ifdef __cpp_lib_three_way_comparison
757 friend constexpr auto
758 operator<=>(const _Iterator& __x, const _Iterator& __y)
759 requires totally_ordered<_Winc> && three_way_comparable<_Winc>
760 { return __x._M_value <=> __y._M_value; }
763 friend constexpr _Iterator
764 operator+(_Iterator __i, difference_type __n)
765 requires __detail::__advanceable<_Winc>
766 { return __i += __n; }
768 friend constexpr _Iterator
769 operator+(difference_type __n, _Iterator __i)
770 requires __detail::__advanceable<_Winc>
771 { return __i += __n; }
773 friend constexpr _Iterator
774 operator-(_Iterator __i, difference_type __n)
775 requires __detail::__advanceable<_Winc>
776 { return __i -= __n; }
778 friend constexpr difference_type
779 operator-(const _Iterator& __x, const _Iterator& __y)
780 requires __detail::__advanceable<_Winc>
782 using __detail::__is_integer_like;
783 using __detail::__is_signed_integer_like;
784 using _Dt = difference_type;
785 if constexpr (__is_integer_like<_Winc>)
787 if constexpr (__is_signed_integer_like<_Winc>)
788 return _Dt(_Dt(__x._M_value) - _Dt(__y._M_value));
790 return (__y._M_value > __x._M_value)
791 ? _Dt(-_Dt(__y._M_value - __x._M_value))
792 : _Dt(__x._M_value - __y._M_value);
795 return __x._M_value - __y._M_value;
799 _Winc _M_value = _Winc();
808 _M_equal(const _Iterator& __x) const
809 { return __x._M_value == _M_bound; }
811 _Bound _M_bound = _Bound();
814 _Sentinel() = default;
817 _Sentinel(_Bound __bound)
818 : _M_bound(__bound) { }
820 friend constexpr bool
821 operator==(const _Iterator& __x, const _Sentinel& __y)
822 { return __y._M_equal(__x); }
824 friend constexpr iter_difference_t<_Winc>
825 operator-(const _Iterator& __x, const _Sentinel& __y)
826 requires sized_sentinel_for<_Bound, _Winc>
827 { return __x._M_value - __y._M_bound; }
829 friend constexpr iter_difference_t<_Winc>
830 operator-(const _Sentinel& __x, const _Iterator& __y)
831 requires sized_sentinel_for<_Bound, _Winc>
832 { return -(__y - __x); }
835 _Winc _M_value = _Winc();
836 _Bound _M_bound = _Bound();
839 iota_view() = default;
842 iota_view(_Winc __value)
847 iota_view(type_identity_t<_Winc> __value,
848 type_identity_t<_Bound> __bound)
849 : _M_value(__value), _M_bound(__bound)
851 if constexpr (totally_ordered_with<_Winc, _Bound>)
853 __glibcxx_assert( bool(__value <= __bound) );
858 begin() const { return _Iterator{_M_value}; }
863 if constexpr (same_as<_Bound, unreachable_sentinel_t>)
864 return unreachable_sentinel;
866 return _Sentinel{_M_bound};
870 end() const requires same_as<_Winc, _Bound>
871 { return _Iterator{_M_bound}; }
875 requires (same_as<_Winc, _Bound> && __detail::__advanceable<_Winc>)
876 || (integral<_Winc> && integral<_Bound>)
877 || sized_sentinel_for<_Bound, _Winc>
879 using __detail::__is_integer_like;
880 using __detail::__to_unsigned_like;
881 if constexpr (__is_integer_like<_Winc> && __is_integer_like<_Bound>)
882 return (_M_value < 0)
884 ? __to_unsigned_like(-_M_value) - __to_unsigned_like(-_M_bound)
885 : __to_unsigned_like(_M_bound) + __to_unsigned_like(-_M_value))
886 : __to_unsigned_like(_M_bound) - __to_unsigned_like(_M_value);
888 return __to_unsigned_like(_M_bound - _M_value);
892 template<typename _Winc, typename _Bound>
893 requires (!__detail::__is_integer_like<_Winc>
894 || !__detail::__is_integer_like<_Bound>
895 || (__detail::__is_signed_integer_like<_Winc>
896 == __detail::__is_signed_integer_like<_Bound>))
897 iota_view(_Winc, _Bound) -> iota_view<_Winc, _Bound>;
899 template<weakly_incrementable _Winc, semiregular _Bound>
900 inline constexpr bool
901 enable_borrowed_range<iota_view<_Winc, _Bound>> = true;
905 template<typename _Tp>
906 inline constexpr empty_view<_Tp> empty{};
910 template<typename _Tp>
912 operator()(_Tp&& __e) const
913 { return single_view{std::forward<_Tp>(__e)}; }
916 inline constexpr _Single single{};
920 template<typename _Tp>
922 operator()(_Tp&& __e) const
923 { return iota_view{std::forward<_Tp>(__e)}; }
925 template<typename _Tp, typename _Up>
927 operator()(_Tp&& __e, _Up&& __f) const
928 { return iota_view{std::forward<_Tp>(__e), std::forward<_Up>(__f)}; }
931 inline constexpr _Iota iota{};
936 template<typename _Val, typename _CharT, typename _Traits>
937 concept __stream_extractable
938 = requires(basic_istream<_CharT, _Traits>& is, _Val& t) { is >> t; };
939 } // namespace __detail
941 template<movable _Val, typename _CharT, typename _Traits>
942 requires default_initializable<_Val>
943 && __detail::__stream_extractable<_Val, _CharT, _Traits>
944 class basic_istream_view
945 : public view_interface<basic_istream_view<_Val, _CharT, _Traits>>
948 basic_istream_view() = default;
951 basic_istream_view(basic_istream<_CharT, _Traits>& __stream)
952 : _M_stream(std::__addressof(__stream))
958 if (_M_stream != nullptr)
959 *_M_stream >> _M_object;
960 return _Iterator{*this};
963 constexpr default_sentinel_t
965 { return default_sentinel; }
968 basic_istream<_CharT, _Traits>* _M_stream = nullptr;
969 _Val _M_object = _Val();
974 using iterator_concept = input_iterator_tag;
975 using difference_type = ptrdiff_t;
976 using value_type = _Val;
978 _Iterator() = default;
981 _Iterator(basic_istream_view& __parent) noexcept
982 : _M_parent(std::__addressof(__parent))
985 _Iterator(const _Iterator&) = delete;
986 _Iterator(_Iterator&&) = default;
987 _Iterator& operator=(const _Iterator&) = delete;
988 _Iterator& operator=(_Iterator&&) = default;
993 __glibcxx_assert(_M_parent->_M_stream != nullptr);
994 *_M_parent->_M_stream >> _M_parent->_M_object;
1005 __glibcxx_assert(_M_parent->_M_stream != nullptr);
1006 return _M_parent->_M_object;
1010 operator==(const _Iterator& __x, default_sentinel_t)
1011 { return __x._M_at_end(); }
1014 basic_istream_view* _M_parent = nullptr;
1018 { return _M_parent == nullptr || !*_M_parent->_M_stream; }
1024 template<typename _Val, typename _CharT, typename _Traits>
1025 basic_istream_view<_Val, _CharT, _Traits>
1026 istream_view(basic_istream<_CharT, _Traits>& __s)
1027 { return basic_istream_view<_Val, _CharT, _Traits>{__s}; }
1033 template<bool _NonEmpty, typename _Tp>
1034 using __maybe_empty_t = conditional_t<_NonEmpty, _Tp, _Empty>;
1036 template<bool _Const, typename _Tp>
1037 using __maybe_const_t = conditional_t<_Const, const _Tp, _Tp>;
1039 } // namespace __detail
1045 template<typename _Tp>
1046 inline constexpr auto
1047 __maybe_refwrap(_Tp& __arg)
1048 { return reference_wrapper<_Tp>{__arg}; }
1050 template<typename _Tp>
1051 inline constexpr auto
1052 __maybe_refwrap(const _Tp& __arg)
1053 { return reference_wrapper<const _Tp>{__arg}; }
1055 template<typename _Tp>
1056 inline constexpr decltype(auto)
1057 __maybe_refwrap(_Tp&& __arg)
1058 { return std::forward<_Tp>(__arg); }
1060 template<typename _Callable>
1061 struct _RangeAdaptorClosure;
1063 template<typename _Callable>
1064 struct _RangeAdaptor
1067 [[no_unique_address]]
1068 __detail::__maybe_empty_t<!is_default_constructible_v<_Callable>,
1069 _Callable> _M_callable;
1073 _RangeAdaptor(const _Callable& = {})
1074 requires is_default_constructible_v<_Callable>
1078 _RangeAdaptor(_Callable __callable)
1079 requires (!is_default_constructible_v<_Callable>)
1080 : _M_callable(std::move(__callable))
1083 template<typename... _Args>
1084 requires (sizeof...(_Args) >= 1)
1086 operator()(_Args&&... __args) const
1088 // [range.adaptor.object]: If a range adaptor object accepts more
1089 // than one argument, then the following expressions are equivalent:
1091 // (1) adaptor(range, args...)
1092 // (2) adaptor(args...)(range)
1093 // (3) range | adaptor(args...)
1095 // In this case, adaptor(args...) is a range adaptor closure object.
1097 // We handle (1) and (2) here, and (3) is just a special case of a
1098 // more general case already handled by _RangeAdaptorClosure.
1099 if constexpr (is_invocable_v<_Callable, _Args...>)
1101 static_assert(sizeof...(_Args) != 1,
1102 "a _RangeAdaptor that accepts only one argument "
1103 "should be defined as a _RangeAdaptorClosure");
1104 // Here we handle adaptor(range, args...) -- just forward all
1105 // arguments to the underlying adaptor routine.
1106 return _Callable{}(std::forward<_Args>(__args)...);
1110 // Here we handle adaptor(args...)(range).
1111 // Given args..., we return a _RangeAdaptorClosure that takes a
1112 // range argument, such that (2) is equivalent to (1).
1114 // We need to be careful about how we capture args... in this
1115 // closure. By using __maybe_refwrap, we capture lvalue
1116 // references by reference (through a reference_wrapper) and
1117 // otherwise capture by value.
1119 = [...__args(__maybe_refwrap(std::forward<_Args>(__args)))]
1120 <typename _Range> (_Range&& __r) {
1121 // This static_cast has two purposes: it forwards a
1122 // reference_wrapper<T> capture as a T&, and otherwise
1123 // forwards the captured argument as an rvalue.
1124 return _Callable{}(std::forward<_Range>(__r),
1125 (static_cast<unwrap_reference_t
1126 <remove_const_t<decltype(__args)>>>
1129 using _ClosureType = decltype(__closure);
1130 return _RangeAdaptorClosure<_ClosureType>(std::move(__closure));
1135 template<typename _Callable>
1136 _RangeAdaptor(_Callable) -> _RangeAdaptor<_Callable>;
1138 template<typename _Callable>
1139 struct _RangeAdaptorClosure : public _RangeAdaptor<_Callable>
1141 using _RangeAdaptor<_Callable>::_RangeAdaptor;
1143 template<viewable_range _Range>
1144 requires requires { declval<_Callable>()(declval<_Range>()); }
1146 operator()(_Range&& __r) const
1148 if constexpr (is_default_constructible_v<_Callable>)
1149 return _Callable{}(std::forward<_Range>(__r));
1151 return this->_M_callable(std::forward<_Range>(__r));
1154 template<viewable_range _Range>
1155 requires requires { declval<_Callable>()(declval<_Range>()); }
1156 friend constexpr auto
1157 operator|(_Range&& __r, const _RangeAdaptorClosure& __o)
1158 { return __o(std::forward<_Range>(__r)); }
1160 template<typename _Tp>
1161 friend constexpr auto
1162 operator|(const _RangeAdaptorClosure<_Tp>& __x,
1163 const _RangeAdaptorClosure& __y)
1165 if constexpr (is_default_constructible_v<_Tp>
1166 && is_default_constructible_v<_Callable>)
1168 auto __closure = [] <typename _Up> (_Up&& __e) {
1169 return std::forward<_Up>(__e) | decltype(__x){} | decltype(__y){};
1171 return _RangeAdaptorClosure<decltype(__closure)>(__closure);
1173 else if constexpr (is_default_constructible_v<_Tp>
1174 && !is_default_constructible_v<_Callable>)
1176 auto __closure = [__y] <typename _Up> (_Up&& __e) {
1177 return std::forward<_Up>(__e) | decltype(__x){} | __y;
1179 return _RangeAdaptorClosure<decltype(__closure)>(__closure);
1181 else if constexpr (!is_default_constructible_v<_Tp>
1182 && is_default_constructible_v<_Callable>)
1184 auto __closure = [__x] <typename _Up> (_Up&& __e) {
1185 return std::forward<_Up>(__e) | __x | decltype(__y){};
1187 return _RangeAdaptorClosure<decltype(__closure)>(__closure);
1191 auto __closure = [__x, __y] <typename _Up> (_Up&& __e) {
1192 return std::forward<_Up>(__e) | __x | __y;
1194 return _RangeAdaptorClosure<decltype(__closure)>(__closure);
1199 template<typename _Callable>
1200 _RangeAdaptorClosure(_Callable) -> _RangeAdaptorClosure<_Callable>;
1201 } // namespace __adaptor
1202 } // namespace views
1204 template<range _Range> requires is_object_v<_Range>
1205 class ref_view : public view_interface<ref_view<_Range>>
1208 _Range* _M_r = nullptr;
1210 static void _S_fun(_Range&); // not defined
1211 static void _S_fun(_Range&&) = delete;
1215 ref_view() noexcept = default;
1217 template<__detail::__not_same_as<ref_view> _Tp>
1218 requires convertible_to<_Tp, _Range&>
1219 && requires { _S_fun(declval<_Tp>()); }
1222 : _M_r(std::__addressof(static_cast<_Range&>(std::forward<_Tp>(__t))))
1229 constexpr iterator_t<_Range>
1231 { return ranges::begin(*_M_r); }
1233 constexpr sentinel_t<_Range>
1235 { return ranges::end(*_M_r); }
1238 empty() const requires requires { ranges::empty(*_M_r); }
1239 { return ranges::empty(*_M_r); }
1242 size() const requires sized_range<_Range>
1243 { return ranges::size(*_M_r); }
1246 data() const requires contiguous_range<_Range>
1247 { return ranges::data(*_M_r); }
1250 template<typename _Range>
1251 ref_view(_Range&) -> ref_view<_Range>;
1253 template<typename _Tp>
1254 inline constexpr bool enable_borrowed_range<ref_view<_Tp>> = true;
1258 inline constexpr __adaptor::_RangeAdaptorClosure all
1259 = [] <viewable_range _Range> (_Range&& __r)
1261 if constexpr (view<decay_t<_Range>>)
1262 return std::forward<_Range>(__r);
1263 else if constexpr (requires { ref_view{std::forward<_Range>(__r)}; })
1264 return ref_view{std::forward<_Range>(__r)};
1266 return subrange{std::forward<_Range>(__r)};
1269 template<viewable_range _Range>
1270 using all_t = decltype(all(std::declval<_Range>()));
1272 } // namespace views
1274 // XXX: the following algos are copied from ranges_algo.h to avoid a circular
1275 // dependency with that header.
1278 template<input_iterator _Iter, sentinel_for<_Iter> _Sent,
1279 typename _Proj = identity,
1280 indirect_unary_predicate<projected<_Iter, _Proj>> _Pred>
1282 find_if(_Iter __first, _Sent __last, _Pred __pred, _Proj __proj = {})
1284 while (__first != __last
1285 && !(bool)std::__invoke(__pred, std::__invoke(__proj, *__first)))
1290 template<input_iterator _Iter, sentinel_for<_Iter> _Sent,
1291 typename _Proj = identity,
1292 indirect_unary_predicate<projected<_Iter, _Proj>> _Pred>
1294 find_if_not(_Iter __first, _Sent __last, _Pred __pred, _Proj __proj = {})
1296 while (__first != __last
1297 && (bool)std::__invoke(__pred, std::__invoke(__proj, *__first)))
1302 template<typename _Tp, typename _Proj = identity,
1303 indirect_strict_weak_order<projected<const _Tp*, _Proj>>
1304 _Comp = ranges::less>
1305 constexpr const _Tp&
1306 min(const _Tp& __a, const _Tp& __b, _Comp __comp = {}, _Proj __proj = {})
1308 if (std::__invoke(std::move(__comp),
1309 std::__invoke(__proj, __b),
1310 std::__invoke(__proj, __a)))
1316 template<input_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
1317 input_iterator _Iter2, sentinel_for<_Iter2> _Sent2,
1318 typename _Pred = ranges::equal_to,
1319 typename _Proj1 = identity, typename _Proj2 = identity>
1320 requires indirectly_comparable<_Iter1, _Iter2, _Pred, _Proj1, _Proj2>
1321 constexpr pair<_Iter1, _Iter2>
1322 mismatch(_Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2 __last2,
1323 _Pred __pred = {}, _Proj1 __proj1 = {}, _Proj2 __proj2 = {})
1325 while (__first1 != __last1 && __first2 != __last2
1326 && (bool)std::__invoke(__pred,
1327 std::__invoke(__proj1, *__first1),
1328 std::__invoke(__proj2, *__first2)))
1333 return { std::move(__first1), std::move(__first2) };
1335 } // namespace __detail
1337 template<input_range _Vp,
1338 indirect_unary_predicate<iterator_t<_Vp>> _Pred>
1339 requires view<_Vp> && is_object_v<_Pred>
1340 class filter_view : public view_interface<filter_view<_Vp, _Pred>>
1348 static constexpr auto
1351 if constexpr (bidirectional_range<_Vp>)
1352 return bidirectional_iterator_tag{};
1353 else if constexpr (forward_range<_Vp>)
1354 return forward_iterator_tag{};
1356 return input_iterator_tag{};
1359 static constexpr auto
1362 using _Cat = typename iterator_traits<_Vp_iter>::iterator_category;
1363 if constexpr (derived_from<_Cat, bidirectional_iterator_tag>)
1364 return bidirectional_iterator_tag{};
1365 else if constexpr (derived_from<_Cat, forward_iterator_tag>)
1366 return forward_iterator_tag{};
1373 using _Vp_iter = iterator_t<_Vp>;
1375 _Vp_iter _M_current = _Vp_iter();
1376 filter_view* _M_parent = nullptr;
1379 using iterator_concept = decltype(_S_iter_concept());
1380 using iterator_category = decltype(_S_iter_cat());
1381 using value_type = range_value_t<_Vp>;
1382 using difference_type = range_difference_t<_Vp>;
1384 _Iterator() = default;
1387 _Iterator(filter_view& __parent, _Vp_iter __current)
1388 : _M_current(std::move(__current)),
1389 _M_parent(std::__addressof(__parent))
1394 requires copyable<_Vp_iter>
1395 { return _M_current; }
1399 { return std::move(_M_current); }
1401 constexpr range_reference_t<_Vp>
1403 { return *_M_current; }
1407 requires __detail::__has_arrow<_Vp_iter>
1408 && copyable<_Vp_iter>
1409 { return _M_current; }
1411 constexpr _Iterator&
1414 _M_current = __detail::find_if(std::move(++_M_current),
1415 ranges::end(_M_parent->_M_base),
1416 std::ref(*_M_parent->_M_pred));
1425 operator++(int) requires forward_range<_Vp>
1432 constexpr _Iterator&
1433 operator--() requires bidirectional_range<_Vp>
1437 while (!std::__invoke(*_M_parent->_M_pred, *_M_current));
1442 operator--(int) requires bidirectional_range<_Vp>
1449 friend constexpr bool
1450 operator==(const _Iterator& __x, const _Iterator& __y)
1451 requires equality_comparable<_Vp_iter>
1452 { return __x._M_current == __y._M_current; }
1454 friend constexpr range_rvalue_reference_t<_Vp>
1455 iter_move(const _Iterator& __i)
1456 noexcept(noexcept(ranges::iter_move(__i._M_current)))
1457 { return ranges::iter_move(__i._M_current); }
1459 friend constexpr void
1460 iter_swap(const _Iterator& __x, const _Iterator& __y)
1461 noexcept(noexcept(ranges::iter_swap(__x._M_current, __y._M_current)))
1462 requires indirectly_swappable<_Vp_iter>
1463 { ranges::iter_swap(__x._M_current, __y._M_current); }
1469 sentinel_t<_Vp> _M_end = sentinel_t<_Vp>();
1472 __equal(const _Iterator& __i) const
1473 { return __i._M_current == _M_end; }
1476 _Sentinel() = default;
1479 _Sentinel(filter_view& __parent)
1480 : _M_end(ranges::end(__parent._M_base))
1483 constexpr sentinel_t<_Vp>
1487 friend constexpr bool
1488 operator==(const _Iterator& __x, const _Sentinel& __y)
1489 { return __y.__equal(__x); }
1492 _Vp _M_base = _Vp();
1493 __detail::__box<_Pred> _M_pred;
1496 filter_view() = default;
1499 filter_view(_Vp __base, _Pred __pred)
1500 : _M_base(std::move(__base)), _M_pred(std::move(__pred))
1504 base() const& requires copy_constructible<_Vp>
1509 { return std::move(_M_base); }
1511 constexpr const _Pred&
1513 { return *_M_pred; }
1518 // XXX: we need to cache the result here as per [range.filter.view]
1519 __glibcxx_assert(_M_pred.has_value());
1520 return {*this, __detail::find_if(ranges::begin(_M_base),
1521 ranges::end(_M_base),
1522 std::ref(*_M_pred))};
1528 if constexpr (common_range<_Vp>)
1529 return _Iterator{*this, ranges::end(_M_base)};
1531 return _Sentinel{*this};
1535 template<typename _Range, typename _Pred>
1536 filter_view(_Range&&, _Pred) -> filter_view<views::all_t<_Range>, _Pred>;
1540 inline constexpr __adaptor::_RangeAdaptor filter
1541 = [] <viewable_range _Range, typename _Pred> (_Range&& __r, _Pred&& __p)
1543 return filter_view{std::forward<_Range>(__r), std::forward<_Pred>(__p)};
1545 } // namespace views
1547 template<input_range _Vp, copy_constructible _Fp>
1548 requires view<_Vp> && is_object_v<_Fp>
1549 && regular_invocable<_Fp&, range_reference_t<_Vp>>
1550 && std::__detail::__can_reference<invoke_result_t<_Fp&,
1551 range_reference_t<_Vp>>>
1552 class transform_view : public view_interface<transform_view<_Vp, _Fp>>
1555 template<bool _Const>
1558 template<bool _Const>
1562 using _Parent = __detail::__maybe_const_t<_Const, transform_view>;
1563 using _Base = __detail::__maybe_const_t<_Const, _Vp>;
1565 static constexpr auto
1568 if constexpr (random_access_range<_Vp>)
1569 return random_access_iterator_tag{};
1570 else if constexpr (bidirectional_range<_Vp>)
1571 return bidirectional_iterator_tag{};
1572 else if constexpr (forward_range<_Vp>)
1573 return forward_iterator_tag{};
1575 return input_iterator_tag{};
1578 static constexpr auto
1581 using _Res = invoke_result_t<_Fp&, range_reference_t<_Base>>;
1582 if constexpr (is_lvalue_reference_v<_Res>)
1585 = typename iterator_traits<_Base_iter>::iterator_category;
1586 if constexpr (derived_from<_Cat, contiguous_iterator_tag>)
1587 return random_access_iterator_tag{};
1592 return input_iterator_tag{};
1595 static constexpr decltype(auto)
1596 __iter_move(const _Iterator& __i = {})
1597 noexcept(noexcept(std::__invoke(*__i._M_parent->_M_fun,
1600 if constexpr (is_lvalue_reference_v<decltype(*__i)>)
1601 return std::move(*__i);
1606 using _Base_iter = iterator_t<_Base>;
1608 _Base_iter _M_current = _Base_iter();
1609 _Parent* _M_parent = nullptr;
1612 using iterator_concept = decltype(_S_iter_concept());
1613 using iterator_category = decltype(_S_iter_cat());
1615 = remove_cvref_t<invoke_result_t<_Fp&, range_reference_t<_Base>>>;
1616 using difference_type = range_difference_t<_Base>;
1618 _Iterator() = default;
1621 _Iterator(_Parent& __parent, _Base_iter __current)
1622 : _M_current(std::move(__current)),
1623 _M_parent(std::__addressof(__parent))
1627 _Iterator(_Iterator<!_Const> __i)
1629 && convertible_to<iterator_t<_Vp>, _Base_iter>
1630 : _M_current(std::move(__i._M_current)), _M_parent(__i._M_parent)
1633 constexpr _Base_iter
1635 requires copyable<_Base_iter>
1636 { return _M_current; }
1638 constexpr _Base_iter
1640 { return std::move(_M_current); }
1642 constexpr decltype(auto)
1644 { return std::__invoke(*_M_parent->_M_fun, *_M_current); }
1646 constexpr _Iterator&
1658 operator++(int) requires forward_range<_Base>
1665 constexpr _Iterator&
1666 operator--() requires bidirectional_range<_Base>
1673 operator--(int) requires bidirectional_range<_Base>
1680 constexpr _Iterator&
1681 operator+=(difference_type __n) requires random_access_range<_Base>
1687 constexpr _Iterator&
1688 operator-=(difference_type __n) requires random_access_range<_Base>
1694 constexpr decltype(auto)
1695 operator[](difference_type __n) const
1696 requires random_access_range<_Base>
1697 { return std::__invoke(*_M_parent->_M_fun, _M_current[__n]); }
1699 friend constexpr bool
1700 operator==(const _Iterator& __x, const _Iterator& __y)
1701 requires equality_comparable<_Base_iter>
1702 { return __x._M_current == __y._M_current; }
1704 friend constexpr bool
1705 operator<(const _Iterator& __x, const _Iterator& __y)
1706 requires random_access_range<_Base>
1707 { return __x._M_current < __y._M_current; }
1709 friend constexpr bool
1710 operator>(const _Iterator& __x, const _Iterator& __y)
1711 requires random_access_range<_Base>
1712 { return __y < __x; }
1714 friend constexpr bool
1715 operator<=(const _Iterator& __x, const _Iterator& __y)
1716 requires random_access_range<_Base>
1717 { return !(__y < __x); }
1719 friend constexpr bool
1720 operator>=(const _Iterator& __x, const _Iterator& __y)
1721 requires random_access_range<_Base>
1722 { return !(__x < __y); }
1724 #ifdef __cpp_lib_three_way_comparison
1725 friend constexpr auto
1726 operator<=>(const _Iterator& __x, const _Iterator& __y)
1727 requires random_access_range<_Base>
1728 && three_way_comparable<_Base_iter>
1729 { return __x._M_current <=> __y._M_current; }
1732 friend constexpr _Iterator
1733 operator+(_Iterator __i, difference_type __n)
1734 requires random_access_range<_Base>
1735 { return {*__i._M_parent, __i._M_current + __n}; }
1737 friend constexpr _Iterator
1738 operator+(difference_type __n, _Iterator __i)
1739 requires random_access_range<_Base>
1740 { return {*__i._M_parent, __i._M_current + __n}; }
1742 friend constexpr _Iterator
1743 operator-(_Iterator __i, difference_type __n)
1744 requires random_access_range<_Base>
1745 { return {*__i._M_parent, __i._M_current - __n}; }
1747 friend constexpr difference_type
1748 operator-(const _Iterator& __x, const _Iterator& __y)
1749 requires random_access_range<_Base>
1750 { return __x._M_current - __y._M_current; }
1752 friend constexpr decltype(auto)
1753 iter_move(const _Iterator& __i) noexcept(noexcept(__iter_move()))
1754 { return __iter_move(__i); }
1756 friend constexpr void
1757 iter_swap(const _Iterator& __x, const _Iterator& __y)
1758 noexcept(noexcept(ranges::iter_swap(__x._M_current, __y._M_current)))
1759 requires indirectly_swappable<_Base_iter>
1760 { return ranges::iter_swap(__x._M_current, __y._M_current); }
1762 friend _Sentinel<_Const>;
1765 template<bool _Const>
1769 using _Parent = __detail::__maybe_const_t<_Const, transform_view>;
1770 using _Base = __detail::__maybe_const_t<_Const, _Vp>;
1772 constexpr range_difference_t<_Base>
1773 __distance_from(const _Iterator<_Const>& __i) const
1774 { return _M_end - __i._M_current; }
1777 __equal(const _Iterator<_Const>& __i) const
1778 { return __i._M_current == _M_end; }
1780 sentinel_t<_Base> _M_end = sentinel_t<_Base>();
1783 _Sentinel() = default;
1786 _Sentinel(sentinel_t<_Base> __end)
1791 _Sentinel(_Sentinel<!_Const> __i)
1793 && convertible_to<sentinel_t<_Vp>, sentinel_t<_Base>>
1794 : _M_end(std::move(__i._M_end))
1797 constexpr sentinel_t<_Base>
1801 friend constexpr bool
1802 operator==(const _Iterator<_Const>& __x, const _Sentinel& __y)
1803 { return __y.__equal(__x); }
1805 friend constexpr range_difference_t<_Base>
1806 operator-(const _Iterator<_Const>& __x, const _Sentinel& __y)
1807 requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<_Base>>
1808 { return -__y.__distance_from(__x); }
1810 friend constexpr range_difference_t<_Base>
1811 operator-(const _Sentinel& __y, const _Iterator<_Const>& __x)
1812 requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<_Base>>
1813 { return __y.__distance_from(__x); }
1816 _Vp _M_base = _Vp();
1817 __detail::__box<_Fp> _M_fun;
1820 transform_view() = default;
1823 transform_view(_Vp __base, _Fp __fun)
1824 : _M_base(std::move(__base)), _M_fun(std::move(__fun))
1828 base() const& requires copy_constructible<_Vp>
1829 { return _M_base ; }
1833 { return std::move(_M_base); }
1835 constexpr _Iterator<false>
1837 { return _Iterator<false>{*this, ranges::begin(_M_base)}; }
1839 constexpr _Iterator<true>
1841 requires range<const _Vp>
1842 && regular_invocable<const _Fp&, range_reference_t<const _Vp>>
1843 { return _Iterator<true>{*this, ranges::begin(_M_base)}; }
1845 constexpr _Sentinel<false>
1847 { return _Sentinel<false>{ranges::end(_M_base)}; }
1849 constexpr _Iterator<false>
1850 end() requires common_range<_Vp>
1851 { return _Iterator<false>{*this, ranges::end(_M_base)}; }
1853 constexpr _Sentinel<true>
1855 requires range<const _Vp>
1856 && regular_invocable<const _Fp&, range_reference_t<const _Vp>>
1857 { return _Sentinel<true>{ranges::end(_M_base)}; }
1859 constexpr _Iterator<true>
1861 requires common_range<const _Vp>
1862 && regular_invocable<const _Fp&, range_reference_t<const _Vp>>
1863 { return _Iterator<true>{*this, ranges::end(_M_base)}; }
1866 size() requires sized_range<_Vp>
1867 { return ranges::size(_M_base); }
1870 size() const requires sized_range<const _Vp>
1871 { return ranges::size(_M_base); }
1874 template<typename _Range, typename _Fp>
1875 transform_view(_Range&&, _Fp) -> transform_view<views::all_t<_Range>, _Fp>;
1879 inline constexpr __adaptor::_RangeAdaptor transform
1880 = [] <viewable_range _Range, typename _Fp> (_Range&& __r, _Fp&& __f)
1882 return transform_view{std::forward<_Range>(__r), std::forward<_Fp>(__f)};
1884 } // namespace views
1887 class take_view : public view_interface<take_view<_Vp>>
1890 template<bool _Const>
1894 using _Base = __detail::__maybe_const_t<_Const, _Vp>;
1895 using _CI = counted_iterator<iterator_t<_Base>>;
1897 sentinel_t<_Base> _M_end = sentinel_t<_Base>();
1900 _Sentinel() = default;
1903 _Sentinel(sentinel_t<_Base> __end)
1908 _Sentinel(_Sentinel<!_Const> __s)
1909 requires _Const && convertible_to<sentinel_t<_Vp>, sentinel_t<_Base>>
1910 : _M_end(std::move(__s._M_end))
1913 constexpr sentinel_t<_Base>
1917 friend constexpr bool operator==(const _CI& __y, const _Sentinel& __x)
1918 { return __y.count() == 0 || __y.base() == __x._M_end; }
1921 _Vp _M_base = _Vp();
1922 range_difference_t<_Vp> _M_count = 0;
1925 take_view() = default;
1928 take_view(_Vp base, range_difference_t<_Vp> __count)
1929 : _M_base(std::move(base)), _M_count(std::move(__count))
1933 base() const& requires copy_constructible<_Vp>
1938 { return std::move(_M_base); }
1941 begin() requires (!__detail::__simple_view<_Vp>)
1943 if constexpr (sized_range<_Vp>)
1945 if constexpr (random_access_range<_Vp>)
1946 return ranges::begin(_M_base);
1948 return counted_iterator{ranges::begin(_M_base), size()};
1951 return counted_iterator{ranges::begin(_M_base), _M_count};
1955 begin() const requires range<const _Vp>
1957 if constexpr (sized_range<const _Vp>)
1959 if constexpr (random_access_range<const _Vp>)
1960 return ranges::begin(_M_base);
1962 return counted_iterator{ranges::begin(_M_base), size()};
1965 return counted_iterator{ranges::begin(_M_base), _M_count};
1969 end() requires (!__detail::__simple_view<_Vp>)
1971 if constexpr (sized_range<_Vp>)
1973 if constexpr (random_access_range<_Vp>)
1974 return ranges::begin(_M_base) + size();
1976 return default_sentinel;
1979 return _Sentinel<false>{ranges::end(_M_base)};
1983 end() const requires range<const _Vp>
1985 if constexpr (sized_range<const _Vp>)
1987 if constexpr (random_access_range<const _Vp>)
1988 return ranges::begin(_M_base) + size();
1990 return default_sentinel;
1993 return _Sentinel<true>{ranges::end(_M_base)};
1997 size() requires sized_range<_Vp>
1999 auto __n = ranges::size(_M_base);
2000 return __detail::min(__n, static_cast<decltype(__n)>(_M_count));
2004 size() const requires sized_range<const _Vp>
2006 auto __n = ranges::size(_M_base);
2007 return __detail::min(__n, static_cast<decltype(__n)>(_M_count));
2011 template<range _Range>
2012 take_view(_Range&&, range_difference_t<_Range>)
2013 -> take_view<views::all_t<_Range>>;
2017 inline constexpr __adaptor::_RangeAdaptor take
2018 = [] <viewable_range _Range, typename _Tp> (_Range&& __r, _Tp&& __n)
2020 return take_view{std::forward<_Range>(__r), std::forward<_Tp>(__n)};
2022 } // namespace views
2024 template<view _Vp, typename _Pred>
2025 requires input_range<_Vp> && is_object_v<_Pred>
2026 && indirect_unary_predicate<const _Pred, iterator_t<_Vp>>
2027 class take_while_view : public view_interface<take_while_view<_Vp, _Pred>>
2029 template<bool _Const>
2033 using _Base = __detail::__maybe_const_t<_Const, _Vp>;
2035 sentinel_t<_Base> _M_end = sentinel_t<_Base>();
2036 const _Pred* _M_pred = nullptr;
2039 _Sentinel() = default;
2042 _Sentinel(sentinel_t<_Base> __end, const _Pred* __pred)
2043 : _M_end(__end), _M_pred(__pred)
2047 _Sentinel(_Sentinel<!_Const> __s)
2048 requires _Const && convertible_to<sentinel_t<_Vp>, sentinel_t<_Base>>
2049 : _M_end(__s._M_end), _M_pred(__s._M_pred)
2052 constexpr sentinel_t<_Base>
2053 base() const { return _M_end; }
2055 friend constexpr bool
2056 operator==(const iterator_t<_Base>& __x, const _Sentinel& __y)
2057 { return __y._M_end == __x || !std::__invoke(*__y._M_pred, *__x); }
2060 _Vp _M_base = _Vp();
2061 __detail::__box<_Pred> _M_pred;
2064 take_while_view() = default;
2067 take_while_view(_Vp base, _Pred __pred)
2068 : _M_base(std::move(base)), _M_pred(std::move(__pred))
2073 base() const& requires copy_constructible<_Vp>
2078 { return std::move(_M_base); }
2080 constexpr const _Pred&
2082 { return *_M_pred; }
2085 begin() requires (!__detail::__simple_view<_Vp>)
2086 { return ranges::begin(_M_base); }
2089 begin() const requires range<const _Vp>
2090 { return ranges::begin(_M_base); }
2093 end() requires (!__detail::__simple_view<_Vp>)
2094 { return _Sentinel<false>(ranges::end(_M_base),
2095 std::__addressof(*_M_pred)); }
2098 end() const requires range<const _Vp>
2099 { return _Sentinel<true>(ranges::end(_M_base),
2100 std::__addressof(*_M_pred)); }
2103 template<typename _Range, typename _Pred>
2104 take_while_view(_Range&&, _Pred)
2105 -> take_while_view<views::all_t<_Range>, _Pred>;
2109 inline constexpr __adaptor::_RangeAdaptor take_while
2110 = [] <viewable_range _Range, typename _Pred> (_Range&& __r, _Pred&& __p)
2112 return take_while_view{std::forward<_Range>(__r), std::forward<_Pred>(__p)};
2114 } // namespace views
2117 class drop_view : public view_interface<drop_view<_Vp>>
2120 _Vp _M_base = _Vp();
2121 range_difference_t<_Vp> _M_count = 0;
2124 drop_view() = default;
2127 drop_view(_Vp __base, range_difference_t<_Vp> __count)
2128 : _M_base(std::move(__base)), _M_count(__count)
2129 { __glibcxx_assert(__count >= 0); }
2132 base() const& requires copy_constructible<_Vp>
2137 { return std::move(_M_base); }
2140 begin() requires (!(__detail::__simple_view<_Vp>
2141 && random_access_range<_Vp>))
2143 // XXX: we need to cache the result here as per [range.drop.view]
2144 return ranges::next(ranges::begin(_M_base), _M_count,
2145 ranges::end(_M_base));
2149 begin() const requires random_access_range<const _Vp>
2151 return ranges::next(ranges::begin(_M_base), _M_count,
2152 ranges::end(_M_base));
2156 end() requires (!__detail::__simple_view<_Vp>)
2157 { return ranges::end(_M_base); }
2160 end() const requires range<const _Vp>
2161 { return ranges::end(_M_base); }
2164 size() requires sized_range<_Vp>
2166 const auto __s = ranges::size(_M_base);
2167 const auto __c = static_cast<decltype(__s)>(_M_count);
2168 return __s < __c ? 0 : __s - __c;
2172 size() const requires sized_range<const _Vp>
2174 const auto __s = ranges::size(_M_base);
2175 const auto __c = static_cast<decltype(__s)>(_M_count);
2176 return __s < __c ? 0 : __s - __c;
2180 template<typename _Range>
2181 drop_view(_Range&&, range_difference_t<_Range>)
2182 -> drop_view<views::all_t<_Range>>;
2186 inline constexpr __adaptor::_RangeAdaptor drop
2187 = [] <viewable_range _Range, typename _Tp> (_Range&& __r, _Tp&& __n)
2189 return drop_view{std::forward<_Range>(__r), std::forward<_Tp>(__n)};
2191 } // namespace views
2193 template<view _Vp, typename _Pred>
2194 requires input_range<_Vp> && is_object_v<_Pred>
2195 && indirect_unary_predicate<const _Pred, iterator_t<_Vp>>
2196 class drop_while_view : public view_interface<drop_while_view<_Vp, _Pred>>
2199 _Vp _M_base = _Vp();
2200 __detail::__box<_Pred> _M_pred;
2203 drop_while_view() = default;
2206 drop_while_view(_Vp __base, _Pred __pred)
2207 : _M_base(std::move(__base)), _M_pred(std::move(__pred))
2211 base() const& requires copy_constructible<_Vp>
2216 { return std::move(_M_base); }
2218 constexpr const _Pred&
2220 { return *_M_pred; }
2225 // XXX: we need to cache the result here as per [range.drop.while.view]
2226 return __detail::find_if_not(ranges::begin(_M_base),
2227 ranges::end(_M_base),
2228 std::cref(*_M_pred));
2233 { return ranges::end(_M_base); }
2236 template<typename _Range, typename _Pred>
2237 drop_while_view(_Range&&, _Pred)
2238 -> drop_while_view<views::all_t<_Range>, _Pred>;
2242 inline constexpr __adaptor::_RangeAdaptor drop_while
2243 = [] <viewable_range _Range, typename _Pred> (_Range&& __r, _Pred&& __p)
2245 return drop_while_view{std::forward<_Range>(__r),
2246 std::forward<_Pred>(__p)};
2248 } // namespace views
2250 template<input_range _Vp>
2251 requires view<_Vp> && input_range<range_reference_t<_Vp>>
2252 && (is_reference_v<range_reference_t<_Vp>>
2253 || view<range_value_t<_Vp>>)
2254 class join_view : public view_interface<join_view<_Vp>>
2257 using _InnerRange = range_reference_t<_Vp>;
2259 template<bool _Const>
2262 template<bool _Const>
2266 using _Parent = __detail::__maybe_const_t<_Const, join_view>;
2267 using _Base = __detail::__maybe_const_t<_Const, _Vp>;
2269 static constexpr bool _S_ref_is_glvalue
2270 = is_reference_v<range_reference_t<_Base>>;
2275 auto __update_inner = [this] (range_reference_t<_Base> __x) -> auto&
2277 if constexpr (_S_ref_is_glvalue)
2280 return (_M_parent->_M_inner = views::all(std::move(__x)));
2283 for (; _M_outer != ranges::end(_M_parent->_M_base); ++_M_outer)
2285 auto& inner = __update_inner(*_M_outer);
2286 _M_inner = ranges::begin(inner);
2287 if (_M_inner != ranges::end(inner))
2291 if constexpr (_S_ref_is_glvalue)
2292 _M_inner = _Inner_iter();
2295 static constexpr auto
2298 if constexpr (_S_ref_is_glvalue
2299 && bidirectional_range<_Base>
2300 && bidirectional_range<range_reference_t<_Base>>)
2301 return bidirectional_iterator_tag{};
2302 else if constexpr (_S_ref_is_glvalue
2303 && forward_range<_Base>
2304 && forward_range<range_reference_t<_Base>>)
2305 return forward_iterator_tag{};
2307 return input_iterator_tag{};
2310 static constexpr auto
2314 = typename iterator_traits<_Outer_iter>::iterator_category;
2316 = typename iterator_traits<_Inner_iter>::iterator_category;
2317 if constexpr (_S_ref_is_glvalue
2318 && derived_from<_OuterCat, bidirectional_iterator_tag>
2319 && derived_from<_InnerCat, bidirectional_iterator_tag>)
2320 return bidirectional_iterator_tag{};
2321 else if constexpr (_S_ref_is_glvalue
2322 && derived_from<_OuterCat, forward_iterator_tag>
2323 && derived_from<_InnerCat, forward_iterator_tag>)
2324 return forward_iterator_tag{};
2325 else if constexpr (derived_from<_OuterCat, input_iterator_tag>
2326 && derived_from<_InnerCat, input_iterator_tag>)
2327 return input_iterator_tag{};
2329 return output_iterator_tag{};
2332 using _Outer_iter = iterator_t<_Base>;
2333 using _Inner_iter = iterator_t<range_reference_t<_Base>>;
2335 _Outer_iter _M_outer = _Outer_iter();
2336 _Inner_iter _M_inner = _Inner_iter();
2337 _Parent* _M_parent = nullptr;
2340 using iterator_concept = decltype(_S_iter_concept());
2341 using iterator_category = decltype(_S_iter_cat());
2342 using value_type = range_value_t<range_reference_t<_Base>>;
2343 using difference_type
2344 = common_type_t<range_difference_t<_Base>,
2345 range_difference_t<range_reference_t<_Base>>>;
2347 _Iterator() = default;
2350 _Iterator(_Parent& __parent, _Outer_iter __outer)
2351 : _M_outer(std::move(__outer)),
2352 _M_parent(std::__addressof(__parent))
2356 _Iterator(_Iterator<!_Const> __i)
2358 && convertible_to<iterator_t<_Vp>, _Outer_iter>
2359 && convertible_to<iterator_t<_InnerRange>, _Inner_iter>
2360 : _M_outer(std::move(__i._M_outer)), _M_inner(__i._M_inner),
2361 _M_parent(__i._M_parent)
2364 constexpr decltype(auto)
2366 { return *_M_inner; }
2368 constexpr _Outer_iter
2370 requires __detail::__has_arrow<_Outer_iter>
2371 && copyable<_Outer_iter>
2372 { return _M_inner; }
2374 constexpr _Iterator&
2377 auto&& __inner_range = [this] () -> decltype(auto) {
2378 if constexpr (_S_ref_is_glvalue)
2381 return _M_parent->_M_inner;
2383 if (++_M_inner == ranges::end(__inner_range))
2397 requires _S_ref_is_glvalue && forward_range<_Base>
2398 && forward_range<range_reference_t<_Base>>
2405 constexpr _Iterator&
2407 requires _S_ref_is_glvalue && bidirectional_range<_Base>
2408 && bidirectional_range<range_reference_t<_Base>>
2409 && common_range<range_reference_t<_Base>>
2411 if (_M_outer == ranges::end(_M_parent->_M_base))
2412 _M_inner = ranges::end(*--_M_outer);
2413 while (_M_inner == ranges::begin(*_M_outer))
2414 _M_inner = ranges::end(*--_M_outer);
2421 requires _S_ref_is_glvalue && bidirectional_range<_Base>
2422 && bidirectional_range<range_reference_t<_Base>>
2423 && common_range<range_reference_t<_Base>>
2430 friend constexpr bool
2431 operator==(const _Iterator& __x, const _Iterator& __y)
2432 requires _S_ref_is_glvalue
2433 && equality_comparable<_Outer_iter>
2434 && equality_comparable<_Inner_iter>
2436 return (__x._M_outer == __y._M_outer
2437 && __x._M_inner == __y._M_inner);
2440 friend constexpr decltype(auto)
2441 iter_move(const _Iterator& __i)
2442 noexcept(noexcept(ranges::iter_move(__i._M_inner)))
2443 { return ranges::iter_move(__i._M_inner); }
2445 friend constexpr void
2446 iter_swap(const _Iterator& __x, const _Iterator& __y)
2447 noexcept(noexcept(ranges::iter_swap(__x._M_inner, __y._M_inner)))
2448 { return ranges::iter_swap(__x._M_inner, __y._M_inner); }
2450 friend _Iterator<!_Const>;
2451 friend _Sentinel<_Const>;
2454 template<bool _Const>
2458 using _Parent = __detail::__maybe_const_t<_Const, join_view>;
2459 using _Base = __detail::__maybe_const_t<_Const, _Vp>;
2462 __equal(const _Iterator<_Const>& __i) const
2463 { return __i._M_outer == _M_end; }
2465 sentinel_t<_Base> _M_end = sentinel_t<_Base>();
2468 _Sentinel() = default;
2471 _Sentinel(_Parent& __parent)
2472 : _M_end(ranges::end(__parent._M_base))
2476 _Sentinel(_Sentinel<!_Const> __s)
2477 requires _Const && convertible_to<sentinel_t<_Vp>, sentinel_t<_Base>>
2478 : _M_end(std::move(__s._M_end))
2481 friend constexpr bool
2482 operator==(const _Iterator<_Const>& __x, const _Sentinel& __y)
2483 { return __y.__equal(__x); }
2486 _Vp _M_base = _Vp();
2488 // XXX: _M_inner is "present only when !is_reference_v<_InnerRange>"
2489 [[no_unique_address]]
2490 __detail::__maybe_empty_t<!is_reference_v<_InnerRange>,
2491 views::all_t<_InnerRange>> _M_inner;
2494 join_view() = default;
2497 join_view(_Vp __base)
2498 : _M_base(std::move(__base))
2502 base() const& requires copy_constructible<_Vp>
2507 { return std::move(_M_base); }
2512 constexpr bool __use_const
2513 = (__detail::__simple_view<_Vp>
2514 && is_reference_v<range_reference_t<_Vp>>);
2515 return _Iterator<__use_const>{*this, ranges::begin(_M_base)};
2520 requires input_range<const _Vp>
2521 && is_reference_v<range_reference_t<const _Vp>>
2523 return _Iterator<true>{*this, ranges::begin(_M_base)};
2529 if constexpr (forward_range<_Vp> && is_reference_v<_InnerRange>
2530 && forward_range<_InnerRange>
2531 && common_range<_Vp> && common_range<_InnerRange>)
2532 return _Iterator<__detail::__simple_view<_Vp>>{*this,
2533 ranges::end(_M_base)};
2535 return _Sentinel<__detail::__simple_view<_Vp>>{*this};
2540 requires input_range<const _Vp>
2541 && is_reference_v<range_reference_t<const _Vp>>
2543 if constexpr (forward_range<const _Vp>
2544 && is_reference_v<range_reference_t<const _Vp>>
2545 && forward_range<range_reference_t<const _Vp>>
2546 && common_range<const _Vp>
2547 && common_range<range_reference_t<const _Vp>>)
2548 return _Iterator<true>{*this, ranges::end(_M_base)};
2550 return _Sentinel<true>{*this};
2554 template<typename _Range>
2555 explicit join_view(_Range&&) -> join_view<views::all_t<_Range>>;
2559 inline constexpr __adaptor::_RangeAdaptorClosure join
2560 = [] <viewable_range _Range> (_Range&& __r)
2562 return join_view{std::forward<_Range>(__r)};
2564 } // namespace views
2569 struct __require_constant;
2571 template<typename _Range>
2572 concept __tiny_range = sized_range<_Range>
2574 { typename __require_constant<remove_reference_t<_Range>::size()>; }
2575 && (remove_reference_t<_Range>::size() <= 1);
2578 template<input_range _Vp, forward_range _Pattern>
2579 requires view<_Vp> && view<_Pattern>
2580 && indirectly_comparable<iterator_t<_Vp>, iterator_t<_Pattern>,
2582 && (forward_range<_Vp> || __detail::__tiny_range<_Pattern>)
2583 class split_view : public view_interface<split_view<_Vp, _Pattern>>
2586 template<bool _Const>
2589 template<bool _Const>
2593 using _Parent = __detail::__maybe_const_t<_Const, split_view>;
2594 using _Base = __detail::__maybe_const_t<_Const, _Vp>;
2598 { return _M_current == ranges::end(_M_parent->_M_base); }
2600 // XXX: [24.7.11.3.1]
2601 // Many of the following specifications refer to the notional member
2602 // current of outer-iterator. current is equivalent to current_ if
2603 // V models forward_range, and parent_->current_ otherwise.
2607 if constexpr (forward_range<_Vp>)
2610 return _M_parent->_M_current;
2616 if constexpr (forward_range<_Vp>)
2619 return _M_parent->_M_current;
2622 _Parent* _M_parent = nullptr;
2624 // XXX: _M_current is present only if "V models forward_range"
2625 [[no_unique_address]]
2626 __detail::__maybe_empty_t<forward_range<_Vp>,
2627 iterator_t<_Base>> _M_current;
2630 using iterator_concept = conditional_t<forward_range<_Base>,
2631 forward_iterator_tag,
2632 input_iterator_tag>;
2633 using iterator_category = input_iterator_tag;
2634 using difference_type = range_difference_t<_Base>;
2636 struct value_type : view_interface<value_type>
2639 _OuterIter _M_i = _OuterIter();
2642 value_type() = default;
2645 value_type(_OuterIter __i)
2646 : _M_i(std::move(__i))
2649 constexpr _InnerIter<_Const>
2651 requires copyable<_OuterIter>
2652 { return _InnerIter<_Const>{_M_i}; }
2654 constexpr _InnerIter<_Const>
2656 requires (!copyable<_OuterIter>)
2657 { return _InnerIter<_Const>{std::move(_M_i)}; }
2659 constexpr default_sentinel_t
2661 { return default_sentinel; }
2664 _OuterIter() = default;
2667 _OuterIter(_Parent& __parent) requires (!forward_range<_Base>)
2668 : _M_parent(address(__parent))
2672 _OuterIter(_Parent& __parent, iterator_t<_Base> __current)
2673 requires forward_range<_Base>
2674 : _M_parent(std::__addressof(__parent)),
2675 _M_current(std::move(__current))
2679 _OuterIter(_OuterIter<!_Const> __i)
2681 && convertible_to<iterator_t<_Vp>, iterator_t<_Base>>
2682 : _M_parent(__i._M_parent), _M_current(std::move(__i._M_current))
2685 constexpr value_type
2687 { return value_type{*this}; }
2689 constexpr _OuterIter&
2692 const auto __end = ranges::end(_M_parent->_M_base);
2693 if (_M_current == __end)
2695 const auto [__pbegin, __pend] = subrange{_M_parent->_M_pattern};
2696 if (__pbegin == __pend)
2702 = __detail::mismatch(std::move(_M_current), __end,
2704 _M_current = std::move(__b);
2707 } while (++_M_current != __end);
2711 constexpr decltype(auto)
2714 if constexpr (forward_range<_Base>)
2724 friend constexpr bool
2725 operator==(const _OuterIter& __x, const _OuterIter& __y)
2726 requires forward_range<_Base>
2727 { return __x._M_current == __y._M_current; }
2729 friend constexpr bool
2730 operator==(const _OuterIter& __x, default_sentinel_t)
2731 { return __x.__at_end(); };
2733 friend _InnerIter<_Const>;
2736 template<bool _Const>
2740 using _Base = __detail::__maybe_const_t<_Const, _Vp>;
2745 auto [__pcur, __pend] = subrange{_M_i._M_parent->_M_pattern};
2746 auto __end = ranges::end(_M_i._M_parent->_M_base);
2747 if constexpr (__detail::__tiny_range<_Pattern>)
2749 const auto& __cur = _M_i.__current();
2752 if (__pcur == __pend)
2753 return _M_incremented;
2754 return *__cur == *__pcur;
2758 auto __cur = _M_i.__current();
2761 if (__pcur == __pend)
2762 return _M_incremented;
2765 if (*__cur != *__pcur)
2767 if (++__pcur == __pend)
2769 } while (++__cur != __end);
2774 static constexpr auto
2778 = typename iterator_traits<iterator_t<_Base>>::iterator_category;
2779 if constexpr (derived_from<_Cat, forward_iterator_tag>)
2780 return forward_iterator_tag{};
2785 static constexpr decltype(auto)
2786 __iter_move(const _InnerIter& __i = {})
2787 noexcept(noexcept(ranges::iter_move(__i._M_i.__current())))
2788 { return ranges::iter_move(__i._M_i.__current()); }
2790 static constexpr void
2791 __iter_swap(const _InnerIter& __x = {}, const _InnerIter& __y = {})
2792 noexcept(noexcept(ranges::iter_swap(__x._M_i.__current(),
2793 __y._M_i.__current())))
2794 { ranges::iter_swap(__x._M_i.__current(), __y._M_i.__current()); }
2796 _OuterIter<_Const> _M_i = _OuterIter<_Const>();
2797 bool _M_incremented = false;
2800 using iterator_concept
2801 = typename _OuterIter<_Const>::iterator_concept;
2802 using iterator_category = decltype(_S_iter_cat());
2803 using value_type = range_value_t<_Base>;
2804 using difference_type = range_difference_t<_Base>;
2806 _InnerIter() = default;
2809 _InnerIter(_OuterIter<_Const> __i)
2810 : _M_i(std::move(__i))
2813 constexpr decltype(auto)
2815 { return *_M_i._M_current; }
2817 constexpr _InnerIter&
2820 _M_incremented = true;
2821 if constexpr (!forward_range<_Base>)
2822 if constexpr (_Pattern::size() == 0)
2828 constexpr decltype(auto)
2831 if constexpr (forward_range<_Vp>)
2841 friend constexpr bool
2842 operator==(const _InnerIter& __x, const _InnerIter& __y)
2843 requires forward_range<_Base>
2844 { return __x._M_i == __y._M_i; }
2846 friend constexpr bool
2847 operator==(const _InnerIter& __x, default_sentinel_t)
2848 { return __x.__at_end(); }
2850 friend constexpr decltype(auto)
2851 iter_move(const _InnerIter& __i) noexcept(noexcept(__iter_move()))
2852 { return __iter_move(__i); }
2854 friend constexpr void
2855 iter_swap(const _InnerIter& __x, const _InnerIter& __y)
2856 noexcept(noexcept(__iter_swap()))
2857 requires indirectly_swappable<iterator_t<_Base>>
2858 { __iter_swap(__x, __y); }
2861 _Vp _M_base = _Vp();
2862 _Pattern _M_pattern = _Pattern();
2864 // XXX: _M_current is "present only if !forward_range<V>"
2865 [[no_unique_address]]
2866 __detail::__maybe_empty_t<!forward_range<_Vp>, iterator_t<_Vp>>
2871 split_view() = default;
2874 split_view(_Vp __base, _Pattern __pattern)
2875 : _M_base(std::move(__base)), _M_pattern(std::move(__pattern))
2878 template<input_range _Range>
2879 requires constructible_from<_Vp, views::all_t<_Range>>
2880 && constructible_from<_Pattern, single_view<range_value_t<_Range>>>
2882 split_view(_Range&& __r, range_value_t<_Range> __e)
2883 : _M_base(views::all(std::forward<_Range>(__r))),
2884 _M_pattern(std::move(__e))
2888 base() const& requires copy_constructible<_Vp>
2893 { return std::move(_M_base); }
2898 if constexpr (forward_range<_Vp>)
2899 return _OuterIter<__detail::__simple_view<_Vp>>{*this,
2900 ranges::begin(_M_base)};
2903 _M_current = ranges::begin(_M_base);
2904 return _OuterIter<false>{*this};
2909 begin() const requires forward_range<_Vp> && forward_range<const _Vp>
2911 return _OuterIter<true>{*this, ranges::begin(_M_base)};
2915 end() requires forward_range<_Vp> && common_range<_Vp>
2917 return _OuterIter<__detail::__simple_view<_Vp>>{*this, ranges::end(_M_base)};
2923 if constexpr (forward_range<_Vp>
2924 && forward_range<const _Vp>
2925 && common_range<const _Vp>)
2926 return _OuterIter<true>{*this, ranges::end(_M_base)};
2928 return default_sentinel;
2932 template<typename _Range, typename _Pred>
2933 split_view(_Range&&, _Pred&&)
2934 -> split_view<views::all_t<_Range>, views::all_t<_Pred>>;
2936 template<input_range _Range>
2937 split_view(_Range&&, range_value_t<_Range>)
2938 -> split_view<views::all_t<_Range>, single_view<range_value_t<_Range>>>;
2942 inline constexpr __adaptor::_RangeAdaptor split
2943 = [] <viewable_range _Range, typename _Fp> (_Range&& __r, _Fp&& __f)
2945 return split_view{std::forward<_Range>(__r), std::forward<_Fp>(__f)};
2947 } // namespace views
2953 template<input_or_output_iterator _Iter>
2955 operator()(_Iter __i, iter_difference_t<_Iter> __n) const
2957 if constexpr (random_access_iterator<_Iter>)
2958 return subrange{__i, __i + __n};
2960 return subrange{counted_iterator{std::move(__i), __n},
2965 inline constexpr _Counted counted{};
2966 } // namespace views
2969 requires (!common_range<_Vp>) && copyable<iterator_t<_Vp>>
2970 class common_view : public view_interface<common_view<_Vp>>
2973 _Vp _M_base = _Vp();
2976 common_view() = default;
2979 common_view(_Vp __r)
2980 : _M_base(std::move(__r))
2983 /* XXX: LWG 3280 didn't remove this constructor, but I think it should?
2984 template<viewable_range _Range>
2985 requires (!common_range<_Range>)
2986 && constructible_from<_Vp, views::all_t<_Range>>
2988 common_view(_Range&& __r)
2989 : _M_base(views::all(std::forward<_Range>(__r)))
2994 base() const& requires copy_constructible<_Vp>
2999 { return std::move(_M_base); }
3004 if constexpr (random_access_range<_Vp> && sized_range<_Vp>)
3005 return ranges::begin(_M_base);
3007 return common_iterator<iterator_t<_Vp>, sentinel_t<_Vp>>
3008 (ranges::begin(_M_base));
3012 begin() const requires range<const _Vp>
3014 if constexpr (random_access_range<const _Vp> && sized_range<const _Vp>)
3015 return ranges::begin(_M_base);
3017 return common_iterator<iterator_t<const _Vp>, sentinel_t<const _Vp>>
3018 (ranges::begin(_M_base));
3024 if constexpr (random_access_range<_Vp> && sized_range<_Vp>)
3025 return ranges::begin(_M_base) + ranges::size(_M_base);
3027 return common_iterator<iterator_t<_Vp>, sentinel_t<_Vp>>
3028 (ranges::end(_M_base));
3032 end() const requires range<const _Vp>
3034 if constexpr (random_access_range<const _Vp> && sized_range<const _Vp>)
3035 return ranges::begin(_M_base) + ranges::size(_M_base);
3037 return common_iterator<iterator_t<const _Vp>, sentinel_t<const _Vp>>
3038 (ranges::end(_M_base));
3042 size() requires sized_range<_Vp>
3043 { return ranges::size(_M_base); }
3046 size() const requires sized_range<const _Vp>
3047 { return ranges::size(_M_base); }
3050 template<typename _Range>
3051 common_view(_Range&&) -> common_view<views::all_t<_Range>>;
3055 inline constexpr __adaptor::_RangeAdaptorClosure common
3056 = [] <viewable_range _Range> (_Range&& __r)
3058 if constexpr (common_range<_Range>
3059 && requires { views::all(std::forward<_Range>(__r)); })
3060 return views::all(std::forward<_Range>(__r));
3062 return common_view{std::forward<_Range>(__r)};
3065 } // namespace views
3068 requires bidirectional_range<_Vp>
3069 class reverse_view : public view_interface<reverse_view<_Vp>>
3072 _Vp _M_base = _Vp();
3075 reverse_view() = default;
3078 reverse_view(_Vp __r)
3079 : _M_base(std::move(__r))
3083 base() const& requires copy_constructible<_Vp>
3088 { return std::move(_M_base); }
3090 constexpr reverse_iterator<iterator_t<_Vp>>
3093 // XXX: we need to cache the result here as per [range.reverse.view]
3094 return make_reverse_iterator(ranges::next(ranges::begin(_M_base),
3095 ranges::end(_M_base)));
3099 begin() requires common_range<_Vp>
3100 { return make_reverse_iterator(ranges::end(_M_base)); }
3103 begin() const requires common_range<const _Vp>
3104 { return make_reverse_iterator(ranges::end(_M_base)); }
3106 constexpr reverse_iterator<iterator_t<_Vp>>
3108 { return make_reverse_iterator(ranges::begin(_M_base)); }
3111 end() const requires common_range<const _Vp>
3112 { return make_reverse_iterator(ranges::begin(_M_base)); }
3115 size() requires sized_range<_Vp>
3116 { return ranges::size(_M_base); }
3119 size() const requires sized_range<const _Vp>
3120 { return ranges::size(_M_base); }
3123 template<typename _Range>
3124 reverse_view(_Range&&) -> reverse_view<views::all_t<_Range>>;
3131 inline constexpr bool __is_reversible_subrange = false;
3133 template<typename _Iter, subrange_kind _Kind>
3134 inline constexpr bool
3135 __is_reversible_subrange<subrange<reverse_iterator<_Iter>,
3136 reverse_iterator<_Iter>,
3140 inline constexpr bool __is_reverse_view = false;
3142 template<typename _Vp>
3143 inline constexpr bool __is_reverse_view<reverse_view<_Vp>> = true;
3146 inline constexpr __adaptor::_RangeAdaptorClosure reverse
3147 = [] <viewable_range _Range> (_Range&& __r)
3149 using _Tp = remove_cvref_t<_Range>;
3150 if constexpr (__detail::__is_reverse_view<_Tp>)
3151 return std::forward<_Range>(__r).base();
3152 else if constexpr (__detail::__is_reversible_subrange<_Tp>)
3154 using _Iter = decltype(ranges::begin(__r).base());
3155 if constexpr (sized_range<_Tp>)
3156 return subrange<_Iter, _Iter, subrange_kind::sized>
3157 (__r.end().base(), __r.begin().base(), __r.size());
3159 return subrange<_Iter, _Iter, subrange_kind::unsized>
3160 (__r.end().base(), __r.begin().base());
3163 return reverse_view{std::forward<_Range>(__r)};
3165 } // namespace views
3169 template<typename _Tp, size_t _Nm>
3170 concept __has_tuple_element = requires(_Tp __t)
3172 typename tuple_size<_Tp>::type;
3173 requires _Nm < tuple_size_v<_Tp>;
3174 typename tuple_element_t<_Nm, _Tp>;
3175 { std::get<_Nm>(__t) }
3176 -> convertible_to<const tuple_element_t<_Nm, _Tp>&>;
3180 template<input_range _Vp, size_t _Nm>
3182 && __detail::__has_tuple_element<range_value_t<_Vp>, _Nm>
3183 && __detail::__has_tuple_element<remove_reference_t<range_reference_t<_Vp>>,
3185 class elements_view : public view_interface<elements_view<_Vp, _Nm>>
3188 elements_view() = default;
3191 elements_view(_Vp base)
3192 : _M_base(std::move(base))
3196 base() const& requires copy_constructible<_Vp>
3201 { return std::move(_M_base); }
3204 begin() requires (!__detail::__simple_view<_Vp>)
3205 { return _Iterator<false>(ranges::begin(_M_base)); }
3208 begin() const requires __detail::__simple_view<_Vp>
3209 { return _Iterator<true>(ranges::begin(_M_base)); }
3212 end() requires (!__detail::__simple_view<_Vp>)
3213 { return ranges::end(_M_base); }
3216 end() const requires __detail::__simple_view<_Vp>
3217 { return ranges::end(_M_base); }
3220 size() requires sized_range<_Vp>
3221 { return ranges::size(_M_base); }
3224 size() const requires sized_range<const _Vp>
3225 { return ranges::size(_M_base); }
3228 template<bool _Const>
3231 using _Base = __detail::__maybe_const_t<_Const, _Vp>;
3233 iterator_t<_Base> _M_current = iterator_t<_Base>();
3235 friend _Iterator<!_Const>;
3238 using iterator_category
3239 = typename iterator_traits<iterator_t<_Base>>::iterator_category;
3241 = remove_cvref_t<tuple_element_t<_Nm, range_value_t<_Base>>>;
3242 using difference_type = range_difference_t<_Base>;
3244 _Iterator() = default;
3247 _Iterator(iterator_t<_Base> current)
3248 : _M_current(std::move(current))
3252 _Iterator(_Iterator<!_Const> i)
3253 requires _Const && convertible_to<iterator_t<_Vp>, iterator_t<_Base>>
3254 : _M_current(std::move(i._M_current))
3257 constexpr iterator_t<_Base>
3259 requires copyable<iterator_t<_Base>>
3260 { return _M_current; }
3262 constexpr iterator_t<_Base>
3264 { return std::move(_M_current); }
3266 constexpr decltype(auto)
3268 { return std::get<_Nm>(*_M_current); }
3270 constexpr _Iterator&
3278 operator++(int) requires (!forward_range<_Base>)
3282 operator++(int) requires forward_range<_Base>
3289 constexpr _Iterator&
3290 operator--() requires bidirectional_range<_Base>
3297 operator--(int) requires bidirectional_range<_Base>
3304 constexpr _Iterator&
3305 operator+=(difference_type __n)
3306 requires random_access_range<_Base>
3312 constexpr _Iterator&
3313 operator-=(difference_type __n)
3314 requires random_access_range<_Base>
3320 constexpr decltype(auto)
3321 operator[](difference_type __n) const
3322 requires random_access_range<_Base>
3323 { return std::get<_Nm>(*(_M_current + __n)); }
3325 friend constexpr bool
3326 operator==(const _Iterator& __x, const _Iterator& __y)
3327 requires equality_comparable<iterator_t<_Base>>
3328 { return __x._M_current == __y._M_current; }
3330 friend constexpr bool
3331 operator==(const _Iterator& __x, const sentinel_t<_Base>& __y)
3332 { return __x._M_current == __y; }
3334 friend constexpr bool
3335 operator<(const _Iterator& __x, const _Iterator& __y)
3336 requires random_access_range<_Base>
3337 { return __x._M_current < __y._M_current; }
3339 friend constexpr bool
3340 operator>(const _Iterator& __x, const _Iterator& __y)
3341 requires random_access_range<_Base>
3342 { return __y._M_current < __x._M_current; }
3344 friend constexpr bool
3345 operator<=(const _Iterator& __x, const _Iterator& __y)
3346 requires random_access_range<_Base>
3347 { return !(__y._M_current > __x._M_current); }
3349 friend constexpr bool
3350 operator>=(const _Iterator& __x, const _Iterator& __y)
3351 requires random_access_range<_Base>
3352 { return !(__x._M_current > __y._M_current); }
3354 #ifdef __cpp_lib_three_way_comparison
3355 friend constexpr auto
3356 operator<=>(const _Iterator& __x, const _Iterator& __y)
3357 requires random_access_range<_Base>
3358 && three_way_comparable<iterator_t<_Base>>
3359 { return __x._M_current <=> __y._M_current; }
3362 friend constexpr _Iterator
3363 operator+(const _Iterator& __x, difference_type __y)
3364 requires random_access_range<_Base>
3365 { return _Iterator{__x} += __y; }
3367 friend constexpr _Iterator
3368 operator+(difference_type __x, const _Iterator& __y)
3369 requires random_access_range<_Base>
3370 { return __y + __x; }
3372 friend constexpr _Iterator
3373 operator-(const _Iterator& __x, difference_type __y)
3374 requires random_access_range<_Base>
3375 { return _Iterator{__x} -= __y; }
3377 friend constexpr difference_type
3378 operator-(const _Iterator& __x, const _Iterator& __y)
3379 requires random_access_range<_Base>
3380 { return __x._M_current - __y._M_current; }
3382 friend constexpr difference_type
3383 operator-(const _Iterator<_Const>& __x, const sentinel_t<_Base>& __y)
3384 requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<_Base>>
3385 { return __x._M_current - __y; }
3387 friend constexpr difference_type
3388 operator-(const sentinel_t<_Base>& __x, const _Iterator<_Const>& __y)
3389 requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<_Base>>
3390 { return -(__y - __x); }
3393 _Vp _M_base = _Vp();
3396 template<typename _Range>
3397 using keys_view = elements_view<views::all_t<_Range>, 0>;
3399 template<typename _Range>
3400 using values_view = elements_view<views::all_t<_Range>, 1>;
3404 template<size_t _Nm>
3405 inline constexpr __adaptor::_RangeAdaptorClosure elements
3406 = [] <viewable_range _Range> (_Range&& __r)
3408 using _El = elements_view<views::all_t<_Range>, _Nm>;
3409 return _El{std::forward<_Range>(__r)};
3412 inline constexpr __adaptor::_RangeAdaptorClosure keys = elements<0>;
3413 inline constexpr __adaptor::_RangeAdaptorClosure values = elements<1>;
3414 } // namespace views
3416 } // namespace ranges
3418 namespace views = ranges::views;
3420 template<typename _Iter, typename _Sent, ranges::subrange_kind _Kind>
3421 struct tuple_size<ranges::subrange<_Iter, _Sent, _Kind>>
3422 : integral_constant<size_t, 2>
3425 template<typename _Iter, typename _Sent, ranges::subrange_kind _Kind>
3426 struct tuple_element<0, ranges::subrange<_Iter, _Sent, _Kind>>
3427 { using type = _Iter; };
3429 template<typename _Iter, typename _Sent, ranges::subrange_kind _Kind>
3430 struct tuple_element<1, ranges::subrange<_Iter, _Sent, _Kind>>
3431 { using type = _Sent; };
3433 template<typename _Iter, typename _Sent, ranges::subrange_kind _Kind>
3434 struct tuple_element<0, const ranges::subrange<_Iter, _Sent, _Kind>>
3435 { using type = _Iter; };
3437 template<typename _Iter, typename _Sent, ranges::subrange_kind _Kind>
3438 struct tuple_element<1, const ranges::subrange<_Iter, _Sent, _Kind>>
3439 { using type = _Sent; };
3441 _GLIBCXX_END_NAMESPACE_VERSION
3443 #endif // library concepts
3445 #endif /* _GLIBCXX_RANGES */