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.
65 #ifndef __GLIBCPP_INTERNAL_ITERATOR_H
66 #define __GLIBCPP_INTERNAL_ITERATOR_H
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 // _GLIBCPP_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.
140 base() const { return current; }
150 _Iterator __tmp = current;
160 operator->() const { return &(operator*()); }
182 reverse_iterator __tmp = *this;
204 reverse_iterator operator--(int)
206 reverse_iterator __tmp = *this;
217 operator+(difference_type __n) const
218 { return reverse_iterator(current - __n); }
226 operator+=(difference_type __n)
238 operator-(difference_type __n) const
239 { return reverse_iterator(current + __n); }
247 operator-=(difference_type __n)
259 operator[](difference_type __n) const { return *(*this + __n); }
264 * @param x A %reverse_iterator.
265 * @param y A %reverse_iterator.
266 * @return A simple bool.
268 * Reverse iterators forward many operations to their underlying base()
269 * iterators. Others are implemented in terms of one another.
272 template<typename _Iterator>
274 operator==(const reverse_iterator<_Iterator>& __x,
275 const reverse_iterator<_Iterator>& __y)
276 { return __x.base() == __y.base(); }
278 template<typename _Iterator>
280 operator<(const reverse_iterator<_Iterator>& __x,
281 const reverse_iterator<_Iterator>& __y)
282 { return __y.base() < __x.base(); }
284 template<typename _Iterator>
286 operator!=(const reverse_iterator<_Iterator>& __x,
287 const reverse_iterator<_Iterator>& __y)
288 { return !(__x == __y); }
290 template<typename _Iterator>
292 operator>(const reverse_iterator<_Iterator>& __x,
293 const reverse_iterator<_Iterator>& __y)
294 { return __y < __x; }
296 template<typename _Iterator>
298 operator<=(const reverse_iterator<_Iterator>& __x,
299 const reverse_iterator<_Iterator>& __y)
300 { return !(__y < __x); }
302 template<typename _Iterator>
304 operator>=(const reverse_iterator<_Iterator>& __x,
305 const reverse_iterator<_Iterator>& __y)
306 { return !(__x < __y); }
308 template<typename _Iterator>
309 inline typename reverse_iterator<_Iterator>::difference_type
310 operator-(const reverse_iterator<_Iterator>& __x,
311 const reverse_iterator<_Iterator>& __y)
312 { return __y.base() - __x.base(); }
314 template<typename _Iterator>
315 inline reverse_iterator<_Iterator>
316 operator+(typename reverse_iterator<_Iterator>::difference_type __n,
317 const reverse_iterator<_Iterator>& __x)
318 { return reverse_iterator<_Iterator>(__x.base() - __n); }
321 // 24.4.2.2.1 back_insert_iterator
323 * @brief Turns assignment into insertion.
325 * These are output iterators, constructed from a container-of-T.
326 * Assigning a T to the iterator appends it to the container using
329 * Tip: Using the back_inserter function to create these iterators can
332 template<typename _Container>
333 class back_insert_iterator
334 : public iterator<output_iterator_tag, void, void, void, void>
337 _Container* container;
340 /// A nested typedef for the type of whatever container you used.
341 typedef _Container container_type;
343 /// The only way to create this %iterator is with a container.
345 back_insert_iterator(_Container& __x) : container(&__x) { }
348 * @param value An instance of whatever type
349 * container_type::const_reference is; presumably a
350 * reference-to-const T for container<T>.
351 * @return This %iterator, for chained operations.
353 * This kind of %iterator doesn't really have a "position" in the
354 * container (you can think of the position as being permanently at
355 * the end, if you like). Assigning a value to the %iterator will
356 * always append the value to the end of the container.
358 back_insert_iterator&
359 operator=(typename _Container::const_reference __value)
361 container->push_back(__value);
365 /// Simply returns *this.
366 back_insert_iterator&
367 operator*() { return *this; }
369 /// Simply returns *this. (This %iterator does not "move".)
370 back_insert_iterator&
371 operator++() { return *this; }
373 /// Simply returns *this. (This %iterator does not "move".)
375 operator++(int) { return *this; }
379 * @param x A container of arbitrary type.
380 * @return An instance of back_insert_iterator working on @p x.
382 * This wrapper function helps in creating back_insert_iterator instances.
383 * Typing the name of the %iterator requires knowing the precise full
384 * type of the container, which can be tedious and impedes generic
385 * programming. Using this function lets you take advantage of automatic
386 * template parameter deduction, making the compiler match the correct
389 template<typename _Container>
390 inline back_insert_iterator<_Container>
391 back_inserter(_Container& __x)
392 { return back_insert_iterator<_Container>(__x); }
395 * @brief Turns assignment into insertion.
397 * These are output iterators, constructed from a container-of-T.
398 * Assigning a T to the iterator prepends it to the container using
401 * Tip: Using the front_inserter function to create these iterators can
404 template<typename _Container>
405 class front_insert_iterator
406 : public iterator<output_iterator_tag, void, void, void, void>
409 _Container* container;
412 /// A nested typedef for the type of whatever container you used.
413 typedef _Container container_type;
415 /// The only way to create this %iterator is with a container.
416 explicit front_insert_iterator(_Container& __x) : container(&__x) { }
419 * @param value An instance of whatever type
420 * container_type::const_reference is; presumably a
421 * reference-to-const T for container<T>.
422 * @return This %iterator, for chained operations.
424 * This kind of %iterator doesn't really have a "position" in the
425 * container (you can think of the position as being permanently at
426 * the front, if you like). Assigning a value to the %iterator will
427 * always prepend the value to the front of the container.
429 front_insert_iterator&
430 operator=(typename _Container::const_reference __value)
432 container->push_front(__value);
436 /// Simply returns *this.
437 front_insert_iterator&
438 operator*() { return *this; }
440 /// Simply returns *this. (This %iterator does not "move".)
441 front_insert_iterator&
442 operator++() { return *this; }
444 /// Simply returns *this. (This %iterator does not "move".)
445 front_insert_iterator
446 operator++(int) { return *this; }
450 * @param x A container of arbitrary type.
451 * @return An instance of front_insert_iterator working on @p x.
453 * This wrapper function helps in creating front_insert_iterator instances.
454 * Typing the name of the %iterator requires knowing the precise full
455 * type of the container, which can be tedious and impedes generic
456 * programming. Using this function lets you take advantage of automatic
457 * template parameter deduction, making the compiler match the correct
460 template<typename _Container>
461 inline front_insert_iterator<_Container>
462 front_inserter(_Container& __x)
463 { return front_insert_iterator<_Container>(__x); }
466 * @brief Turns assignment into insertion.
468 * These are output iterators, constructed from a container-of-T.
469 * Assigning a T to the iterator inserts it in the container at the
470 * %iterator's position, rather than overwriting the value at that
473 * (Sequences will actually insert a @e copy of the value before the
474 * %iterator's position.)
476 * Tip: Using the inserter function to create these iterators can
479 template<typename _Container>
480 class insert_iterator
481 : public iterator<output_iterator_tag, void, void, void, void>
484 _Container* container;
485 typename _Container::iterator iter;
488 /// A nested typedef for the type of whatever container you used.
489 typedef _Container container_type;
492 * The only way to create this %iterator is with a container and an
493 * initial position (a normal %iterator into the container).
495 insert_iterator(_Container& __x, typename _Container::iterator __i)
496 : container(&__x), iter(__i) {}
499 * @param value An instance of whatever type
500 * container_type::const_reference is; presumably a
501 * reference-to-const T for container<T>.
502 * @return This %iterator, for chained operations.
504 * This kind of %iterator maintains its own position in the
505 * container. Assigning a value to the %iterator will insert the
506 * value into the container at the place before the %iterator.
508 * The position is maintained such that subsequent assignments will
509 * insert values immediately after one another. For example,
511 * // vector v contains A and Z
513 * insert_iterator i (v, ++v.begin());
518 * // vector v contains A, 1, 2, 3, and Z
522 operator=(const typename _Container::const_reference __value)
524 iter = container->insert(iter, __value);
529 /// Simply returns *this.
531 operator*() { return *this; }
533 /// Simply returns *this. (This %iterator does not "move".)
535 operator++() { return *this; }
537 /// Simply returns *this. (This %iterator does not "move".)
539 operator++(int) { return *this; }
543 * @param x A container of arbitrary type.
544 * @return An instance of insert_iterator working on @p x.
546 * This wrapper function helps in creating insert_iterator instances.
547 * Typing the name of the %iterator requires knowing the precise full
548 * type of the container, which can be tedious and impedes generic
549 * programming. Using this function lets you take advantage of automatic
550 * template parameter deduction, making the compiler match the correct
553 template<typename _Container, typename _Iterator>
554 inline insert_iterator<_Container>
555 inserter(_Container& __x, _Iterator __i)
557 return insert_iterator<_Container>(__x,
558 typename _Container::iterator(__i));
564 // This iterator adapter is 'normal' in the sense that it does not
565 // change the semantics of any of the operators of its iterator
566 // parameter. Its primary purpose is to convert an iterator that is
567 // not a class, e.g. a pointer, into an iterator that is a class.
568 // The _Container parameter exists solely so that different containers
569 // using this template can instantiate different types, even if the
570 // _Iterator parameter is the same.
571 using std::iterator_traits;
573 template<typename _Iterator, typename _Container>
574 class __normal_iterator
575 : public iterator<typename iterator_traits<_Iterator>::iterator_category,
576 typename iterator_traits<_Iterator>::value_type,
577 typename iterator_traits<_Iterator>::difference_type,
578 typename iterator_traits<_Iterator>::pointer,
579 typename iterator_traits<_Iterator>::reference>
582 _Iterator _M_current;
585 typedef typename iterator_traits<_Iterator>::difference_type
587 typedef typename iterator_traits<_Iterator>::reference reference;
588 typedef typename iterator_traits<_Iterator>::pointer pointer;
590 __normal_iterator() : _M_current(_Iterator()) { }
593 __normal_iterator(const _Iterator& __i) : _M_current(__i) { }
595 // Allow iterator to const_iterator conversion
596 template<typename _Iter>
597 inline __normal_iterator(const __normal_iterator<_Iter, _Container>& __i)
598 : _M_current(__i.base()) { }
600 // Forward iterator requirements
602 operator*() const { return *_M_current; }
605 operator->() const { return _M_current; }
608 operator++() { ++_M_current; return *this; }
611 operator++(int) { return __normal_iterator(_M_current++); }
613 // Bidirectional iterator requirements
615 operator--() { --_M_current; return *this; }
618 operator--(int) { return __normal_iterator(_M_current--); }
620 // Random access iterator requirements
622 operator[](const difference_type& __n) const
623 { return _M_current[__n]; }
626 operator+=(const difference_type& __n)
627 { _M_current += __n; return *this; }
630 operator+(const difference_type& __n) const
631 { return __normal_iterator(_M_current + __n); }
634 operator-=(const difference_type& __n)
635 { _M_current -= __n; return *this; }
638 operator-(const difference_type& __n) const
639 { return __normal_iterator(_M_current - __n); }
642 base() const { return _M_current; }
645 // Note: In what follows, the left- and right-hand-side iterators are
646 // allowed to vary in types (conceptually in cv-qualification) so that
647 // comparaison between cv-qualified and non-cv-qualified iterators be
648 // valid. However, the greedy and unfriendly operators in std::rel_ops
649 // will make overload resolution ambiguous (when in scope) if we don't
650 // provide overloads whose operands are of the same type. Can someone
651 // remind me what generic programming is about? -- Gaby
653 // Forward iterator requirements
654 template<typename _IteratorL, typename _IteratorR, typename _Container>
656 operator==(const __normal_iterator<_IteratorL, _Container>& __lhs,
657 const __normal_iterator<_IteratorR, _Container>& __rhs)
658 { return __lhs.base() == __rhs.base(); }
660 template<typename _Iterator, typename _Container>
662 operator==(const __normal_iterator<_Iterator, _Container>& __lhs,
663 const __normal_iterator<_Iterator, _Container>& __rhs)
664 { return __lhs.base() == __rhs.base(); }
666 template<typename _IteratorL, typename _IteratorR, typename _Container>
668 operator!=(const __normal_iterator<_IteratorL, _Container>& __lhs,
669 const __normal_iterator<_IteratorR, _Container>& __rhs)
670 { return __lhs.base() != __rhs.base(); }
672 template<typename _Iterator, typename _Container>
674 operator!=(const __normal_iterator<_Iterator, _Container>& __lhs,
675 const __normal_iterator<_Iterator, _Container>& __rhs)
676 { return __lhs.base() != __rhs.base(); }
678 // Random access iterator requirements
679 template<typename _IteratorL, typename _IteratorR, typename _Container>
681 operator<(const __normal_iterator<_IteratorL, _Container>& __lhs,
682 const __normal_iterator<_IteratorR, _Container>& __rhs)
683 { return __lhs.base() < __rhs.base(); }
685 template<typename _Iterator, typename _Container>
687 operator<(const __normal_iterator<_Iterator, _Container>& __lhs,
688 const __normal_iterator<_Iterator, _Container>& __rhs)
689 { return __lhs.base() < __rhs.base(); }
691 template<typename _IteratorL, typename _IteratorR, typename _Container>
693 operator>(const __normal_iterator<_IteratorL, _Container>& __lhs,
694 const __normal_iterator<_IteratorR, _Container>& __rhs)
695 { return __lhs.base() > __rhs.base(); }
697 template<typename _Iterator, typename _Container>
699 operator>(const __normal_iterator<_Iterator, _Container>& __lhs,
700 const __normal_iterator<_Iterator, _Container>& __rhs)
701 { return __lhs.base() > __rhs.base(); }
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 // _GLIBCPP_RESOLVE_LIB_DEFECTS
728 // According to the resolution of DR179 not only the various comparison
729 // operators but also operator- must accept mixed iterator/const_iterator
731 template<typename _IteratorL, typename _IteratorR, typename _Container>
732 inline typename __normal_iterator<_IteratorL, _Container>::difference_type
733 operator-(const __normal_iterator<_IteratorL, _Container>& __lhs,
734 const __normal_iterator<_IteratorR, _Container>& __rhs)
735 { return __lhs.base() - __rhs.base(); }
737 template<typename _Iterator, typename _Container>
738 inline __normal_iterator<_Iterator, _Container>
739 operator+(typename __normal_iterator<_Iterator, _Container>::difference_type __n,
740 const __normal_iterator<_Iterator, _Container>& __i)
741 { return __normal_iterator<_Iterator, _Container>(__i.base() + __n); }
742 } // namespace __gnu_cxx