1 // Iterators -*- C++ -*-
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56 /** @file stl_iterator.h
57 * This is an internal header file, included by other library headers.
58 * You should not attempt to use it directly.
60 * This file implements reverse_iterator, back_insert_iterator,
61 * front_insert_iterator, insert_iterator, __normal_iterator, and their
62 * supporting functions and overloaded operators.
70 // 24.4.1 Reverse iterators
72 * "Bidirectional and random access iterators have corresponding reverse
73 * %iterator adaptors that iterate through the data structure in the
74 * opposite direction. They have the same signatures as the corresponding
75 * iterators. The fundamental relation between a reverse %iterator and its
76 * corresponding %iterator @c i is established by the identity:
78 * &*(reverse_iterator(i)) == &*(i - 1)
81 * This mapping is dictated by the fact that while there is always a
82 * pointer past the end of an array, there might not be a valid pointer
83 * before the beginning of an array." [24.4.1]/1,2
85 * Reverse iterators can be tricky and surprising at first. Their
86 * semantics make sense, however, and the trickiness is a side effect of
87 * the requirement that the iterators must be safe.
89 template<typename _Iterator>
90 class reverse_iterator
91 : public iterator<typename iterator_traits<_Iterator>::iterator_category,
92 typename iterator_traits<_Iterator>::value_type,
93 typename iterator_traits<_Iterator>::difference_type,
94 typename iterator_traits<_Iterator>::pointer,
95 typename iterator_traits<_Iterator>::reference>
101 typedef _Iterator iterator_type;
102 typedef typename iterator_traits<_Iterator>::difference_type
104 typedef typename iterator_traits<_Iterator>::reference reference;
105 typedef typename iterator_traits<_Iterator>::pointer pointer;
109 * The default constructor default-initializes member @p current.
110 * If it is a pointer, that means it is zero-initialized.
112 // _GLIBCXX_RESOLVE_LIB_DEFECTS
113 // 235 No specification of default ctor for reverse_iterator
114 reverse_iterator() : current() { }
117 * This %iterator will move in the opposite direction that @p x does.
120 reverse_iterator(iterator_type __x) : current(__x) { }
123 * The copy constructor is normal.
125 reverse_iterator(const reverse_iterator& __x)
126 : current(__x.current) { }
129 * A reverse_iterator across other types can be copied in the normal
132 template<typename _Iter>
133 reverse_iterator(const reverse_iterator<_Iter>& __x)
134 : current(__x.base()) { }
137 * @return @c current, the %iterator used for underlying work.
151 _Iterator __tmp = current;
162 { return &(operator*()); }
184 reverse_iterator __tmp = *this;
206 reverse_iterator operator--(int)
208 reverse_iterator __tmp = *this;
219 operator+(difference_type __n) const
220 { return reverse_iterator(current - __n); }
228 operator+=(difference_type __n)
240 operator-(difference_type __n) const
241 { return reverse_iterator(current + __n); }
249 operator-=(difference_type __n)
261 operator[](difference_type __n) const
262 { return *(*this + __n); }
267 * @param x A %reverse_iterator.
268 * @param y A %reverse_iterator.
269 * @return A simple bool.
271 * Reverse iterators forward many operations to their underlying base()
272 * iterators. Others are implemented in terms of one another.
275 template<typename _Iterator>
277 operator==(const reverse_iterator<_Iterator>& __x,
278 const reverse_iterator<_Iterator>& __y)
279 { return __x.base() == __y.base(); }
281 template<typename _Iterator>
283 operator<(const reverse_iterator<_Iterator>& __x,
284 const reverse_iterator<_Iterator>& __y)
285 { return __y.base() < __x.base(); }
287 template<typename _Iterator>
289 operator!=(const reverse_iterator<_Iterator>& __x,
290 const reverse_iterator<_Iterator>& __y)
291 { return !(__x == __y); }
293 template<typename _Iterator>
295 operator>(const reverse_iterator<_Iterator>& __x,
296 const reverse_iterator<_Iterator>& __y)
297 { return __y < __x; }
299 template<typename _Iterator>
301 operator<=(const reverse_iterator<_Iterator>& __x,
302 const reverse_iterator<_Iterator>& __y)
303 { return !(__y < __x); }
305 template<typename _Iterator>
307 operator>=(const reverse_iterator<_Iterator>& __x,
308 const reverse_iterator<_Iterator>& __y)
309 { return !(__x < __y); }
311 template<typename _Iterator>
312 inline typename reverse_iterator<_Iterator>::difference_type
313 operator-(const reverse_iterator<_Iterator>& __x,
314 const reverse_iterator<_Iterator>& __y)
315 { return __y.base() - __x.base(); }
317 template<typename _Iterator>
318 inline reverse_iterator<_Iterator>
319 operator+(typename reverse_iterator<_Iterator>::difference_type __n,
320 const reverse_iterator<_Iterator>& __x)
321 { return reverse_iterator<_Iterator>(__x.base() - __n); }
324 // 24.4.2.2.1 back_insert_iterator
326 * @brief Turns assignment into insertion.
328 * These are output iterators, constructed from a container-of-T.
329 * Assigning a T to the iterator appends it to the container using
332 * Tip: Using the back_inserter function to create these iterators can
335 template<typename _Container>
336 class back_insert_iterator
337 : public iterator<output_iterator_tag, void, void, void, void>
340 _Container* container;
343 /// A nested typedef for the type of whatever container you used.
344 typedef _Container container_type;
346 /// The only way to create this %iterator is with a container.
348 back_insert_iterator(_Container& __x) : container(&__x) { }
351 * @param value An instance of whatever type
352 * container_type::const_reference is; presumably a
353 * reference-to-const T for container<T>.
354 * @return This %iterator, for chained operations.
356 * This kind of %iterator doesn't really have a "position" in the
357 * container (you can think of the position as being permanently at
358 * the end, if you like). Assigning a value to the %iterator will
359 * always append the value to the end of the container.
361 back_insert_iterator&
362 operator=(typename _Container::const_reference __value)
364 container->push_back(__value);
368 /// Simply returns *this.
369 back_insert_iterator&
373 /// Simply returns *this. (This %iterator does not "move".)
374 back_insert_iterator&
378 /// Simply returns *this. (This %iterator does not "move".)
385 * @param x A container of arbitrary type.
386 * @return An instance of back_insert_iterator working on @p x.
388 * This wrapper function helps in creating back_insert_iterator instances.
389 * Typing the name of the %iterator requires knowing the precise full
390 * type of the container, which can be tedious and impedes generic
391 * programming. Using this function lets you take advantage of automatic
392 * template parameter deduction, making the compiler match the correct
395 template<typename _Container>
396 inline back_insert_iterator<_Container>
397 back_inserter(_Container& __x)
398 { return back_insert_iterator<_Container>(__x); }
401 * @brief Turns assignment into insertion.
403 * These are output iterators, constructed from a container-of-T.
404 * Assigning a T to the iterator prepends it to the container using
407 * Tip: Using the front_inserter function to create these iterators can
410 template<typename _Container>
411 class front_insert_iterator
412 : public iterator<output_iterator_tag, void, void, void, void>
415 _Container* container;
418 /// A nested typedef for the type of whatever container you used.
419 typedef _Container container_type;
421 /// The only way to create this %iterator is with a container.
422 explicit front_insert_iterator(_Container& __x) : container(&__x) { }
425 * @param value An instance of whatever type
426 * container_type::const_reference is; presumably a
427 * reference-to-const T for container<T>.
428 * @return This %iterator, for chained operations.
430 * This kind of %iterator doesn't really have a "position" in the
431 * container (you can think of the position as being permanently at
432 * the front, if you like). Assigning a value to the %iterator will
433 * always prepend the value to the front of the container.
435 front_insert_iterator&
436 operator=(typename _Container::const_reference __value)
438 container->push_front(__value);
442 /// Simply returns *this.
443 front_insert_iterator&
447 /// Simply returns *this. (This %iterator does not "move".)
448 front_insert_iterator&
452 /// Simply returns *this. (This %iterator does not "move".)
453 front_insert_iterator
459 * @param x A container of arbitrary type.
460 * @return An instance of front_insert_iterator working on @p x.
462 * This wrapper function helps in creating front_insert_iterator instances.
463 * Typing the name of the %iterator requires knowing the precise full
464 * type of the container, which can be tedious and impedes generic
465 * programming. Using this function lets you take advantage of automatic
466 * template parameter deduction, making the compiler match the correct
469 template<typename _Container>
470 inline front_insert_iterator<_Container>
471 front_inserter(_Container& __x)
472 { return front_insert_iterator<_Container>(__x); }
475 * @brief Turns assignment into insertion.
477 * These are output iterators, constructed from a container-of-T.
478 * Assigning a T to the iterator inserts it in the container at the
479 * %iterator's position, rather than overwriting the value at that
482 * (Sequences will actually insert a @e copy of the value before the
483 * %iterator's position.)
485 * Tip: Using the inserter function to create these iterators can
488 template<typename _Container>
489 class insert_iterator
490 : public iterator<output_iterator_tag, void, void, void, void>
493 _Container* container;
494 typename _Container::iterator iter;
497 /// A nested typedef for the type of whatever container you used.
498 typedef _Container container_type;
501 * The only way to create this %iterator is with a container and an
502 * initial position (a normal %iterator into the container).
504 insert_iterator(_Container& __x, typename _Container::iterator __i)
505 : container(&__x), iter(__i) {}
508 * @param value An instance of whatever type
509 * container_type::const_reference is; presumably a
510 * reference-to-const T for container<T>.
511 * @return This %iterator, for chained operations.
513 * This kind of %iterator maintains its own position in the
514 * container. Assigning a value to the %iterator will insert the
515 * value into the container at the place before the %iterator.
517 * The position is maintained such that subsequent assignments will
518 * insert values immediately after one another. For example,
520 * // vector v contains A and Z
522 * insert_iterator i (v, ++v.begin());
527 * // vector v contains A, 1, 2, 3, and Z
531 operator=(const typename _Container::const_reference __value)
533 iter = container->insert(iter, __value);
538 /// Simply returns *this.
543 /// Simply returns *this. (This %iterator does not "move".)
548 /// Simply returns *this. (This %iterator does not "move".)
555 * @param x A container of arbitrary type.
556 * @return An instance of insert_iterator working on @p x.
558 * This wrapper function helps in creating insert_iterator instances.
559 * Typing the name of the %iterator requires knowing the precise full
560 * type of the container, which can be tedious and impedes generic
561 * programming. Using this function lets you take advantage of automatic
562 * template parameter deduction, making the compiler match the correct
565 template<typename _Container, typename _Iterator>
566 inline insert_iterator<_Container>
567 inserter(_Container& __x, _Iterator __i)
569 return insert_iterator<_Container>(__x,
570 typename _Container::iterator(__i));
576 // This iterator adapter is 'normal' in the sense that it does not
577 // change the semantics of any of the operators of its iterator
578 // parameter. Its primary purpose is to convert an iterator that is
579 // not a class, e.g. a pointer, into an iterator that is a class.
580 // The _Container parameter exists solely so that different containers
581 // using this template can instantiate different types, even if the
582 // _Iterator parameter is the same.
583 using std::iterator_traits;
585 template<typename _Iterator, typename _Container>
586 class __normal_iterator
589 _Iterator _M_current;
592 typedef typename iterator_traits<_Iterator>::iterator_category
594 typedef typename iterator_traits<_Iterator>::value_type value_type;
595 typedef typename iterator_traits<_Iterator>::difference_type
597 typedef typename iterator_traits<_Iterator>::reference reference;
598 typedef typename iterator_traits<_Iterator>::pointer pointer;
600 __normal_iterator() : _M_current(_Iterator()) { }
603 __normal_iterator(const _Iterator& __i) : _M_current(__i) { }
605 // Allow iterator to const_iterator conversion
606 template<typename _Iter>
607 inline __normal_iterator(const __normal_iterator<_Iter,
609 : _M_current(__i.base()) { }
611 // Forward iterator requirements
614 { return *_M_current; }
618 { return _M_current; }
629 { return __normal_iterator(_M_current++); }
631 // Bidirectional iterator requirements
641 { return __normal_iterator(_M_current--); }
643 // Random access iterator requirements
645 operator[](const difference_type& __n) const
646 { return _M_current[__n]; }
649 operator+=(const difference_type& __n)
650 { _M_current += __n; return *this; }
653 operator+(const difference_type& __n) const
654 { return __normal_iterator(_M_current + __n); }
657 operator-=(const difference_type& __n)
658 { _M_current -= __n; return *this; }
661 operator-(const difference_type& __n) const
662 { return __normal_iterator(_M_current - __n); }
666 { return _M_current; }
669 // Note: In what follows, the left- and right-hand-side iterators are
670 // allowed to vary in types (conceptually in cv-qualification) so that
671 // comparaison between cv-qualified and non-cv-qualified iterators be
672 // valid. However, the greedy and unfriendly operators in std::rel_ops
673 // will make overload resolution ambiguous (when in scope) if we don't
674 // provide overloads whose operands are of the same type. Can someone
675 // remind me what generic programming is about? -- Gaby
677 // Forward iterator requirements
678 template<typename _IteratorL, typename _IteratorR, typename _Container>
680 operator==(const __normal_iterator<_IteratorL, _Container>& __lhs,
681 const __normal_iterator<_IteratorR, _Container>& __rhs)
682 { return __lhs.base() == __rhs.base(); }
684 template<typename _Iterator, typename _Container>
686 operator==(const __normal_iterator<_Iterator, _Container>& __lhs,
687 const __normal_iterator<_Iterator, _Container>& __rhs)
688 { return __lhs.base() == __rhs.base(); }
690 template<typename _IteratorL, typename _IteratorR, typename _Container>
692 operator!=(const __normal_iterator<_IteratorL, _Container>& __lhs,
693 const __normal_iterator<_IteratorR, _Container>& __rhs)
694 { return __lhs.base() != __rhs.base(); }
696 template<typename _Iterator, typename _Container>
698 operator!=(const __normal_iterator<_Iterator, _Container>& __lhs,
699 const __normal_iterator<_Iterator, _Container>& __rhs)
700 { return __lhs.base() != __rhs.base(); }
702 // Random access iterator requirements
703 template<typename _IteratorL, typename _IteratorR, typename _Container>
705 operator<(const __normal_iterator<_IteratorL, _Container>& __lhs,
706 const __normal_iterator<_IteratorR, _Container>& __rhs)
707 { return __lhs.base() < __rhs.base(); }
709 template<typename _Iterator, typename _Container>
711 operator<(const __normal_iterator<_Iterator, _Container>& __lhs,
712 const __normal_iterator<_Iterator, _Container>& __rhs)
713 { return __lhs.base() < __rhs.base(); }
715 template<typename _IteratorL, typename _IteratorR, typename _Container>
717 operator>(const __normal_iterator<_IteratorL, _Container>& __lhs,
718 const __normal_iterator<_IteratorR, _Container>& __rhs)
719 { return __lhs.base() > __rhs.base(); }
721 template<typename _Iterator, typename _Container>
723 operator>(const __normal_iterator<_Iterator, _Container>& __lhs,
724 const __normal_iterator<_Iterator, _Container>& __rhs)
725 { return __lhs.base() > __rhs.base(); }
727 template<typename _IteratorL, typename _IteratorR, typename _Container>
729 operator<=(const __normal_iterator<_IteratorL, _Container>& __lhs,
730 const __normal_iterator<_IteratorR, _Container>& __rhs)
731 { return __lhs.base() <= __rhs.base(); }
733 template<typename _Iterator, typename _Container>
735 operator<=(const __normal_iterator<_Iterator, _Container>& __lhs,
736 const __normal_iterator<_Iterator, _Container>& __rhs)
737 { return __lhs.base() <= __rhs.base(); }
739 template<typename _IteratorL, typename _IteratorR, typename _Container>
741 operator>=(const __normal_iterator<_IteratorL, _Container>& __lhs,
742 const __normal_iterator<_IteratorR, _Container>& __rhs)
743 { return __lhs.base() >= __rhs.base(); }
745 template<typename _Iterator, typename _Container>
747 operator>=(const __normal_iterator<_Iterator, _Container>& __lhs,
748 const __normal_iterator<_Iterator, _Container>& __rhs)
749 { return __lhs.base() >= __rhs.base(); }
751 // _GLIBCXX_RESOLVE_LIB_DEFECTS
752 // According to the resolution of DR179 not only the various comparison
753 // operators but also operator- must accept mixed iterator/const_iterator
755 template<typename _IteratorL, typename _IteratorR, typename _Container>
756 inline typename __normal_iterator<_IteratorL, _Container>::difference_type
757 operator-(const __normal_iterator<_IteratorL, _Container>& __lhs,
758 const __normal_iterator<_IteratorR, _Container>& __rhs)
759 { return __lhs.base() - __rhs.base(); }
761 template<typename _Iterator, typename _Container>
762 inline __normal_iterator<_Iterator, _Container>
763 operator+(typename __normal_iterator<_Iterator, _Container>::difference_type
764 __n, const __normal_iterator<_Iterator, _Container>& __i)
765 { return __normal_iterator<_Iterator, _Container>(__i.base() + __n); }
766 } // namespace __gnu_cxx