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Side by Side Diff: sdk/lib/core/iterator.dart

Issue 11867024: Move some core classes to collection library. (Closed) Base URL: https://dart.googlecode.com/svn/branches/bleeding_edge/dart
Patch Set: Update status files with bug number. Created 7 years, 11 months ago
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1 // Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file 1 // Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
2 // for details. All rights reserved. Use of this source code is governed by a 2 // for details. All rights reserved. Use of this source code is governed by a
3 // BSD-style license that can be found in the LICENSE file. 3 // BSD-style license that can be found in the LICENSE file.
4 4
5 part of dart.core; 5 part of dart.core;
6 6
7 /** 7 /**
8 * The [Iterator] class provides methods to iterate over an object. It 8 * The [Iterator] class provides methods to iterate over an object. It
9 * is transparently used by the for-in construct to test for the end 9 * is transparently used by the for-in construct to test for the end
10 * of the iteration, and to get the elements. 10 * of the iteration, and to get the elements.
11 * 11 *
12 * If the object iterated over is changed during the iteration, the 12 * If the object iterated over is changed during the iteration, the
13 * behavior is unspecified. 13 * behavior is unspecified.
14 * 14 *
15 * The [Iterator] is initially positioned before the first element. Before 15 * The [Iterator] is initially positioned before the first element. Before
16 * accessing the first element the iterator must thus be advanced ([moveNext]) 16 * accessing the first element the iterator must thus be advanced ([moveNext])
17 * to point to the first element. If there is no element left, then [moveNext] 17 * to point to the first element. If there is no element left, then [moveNext]
18 * returns false. 18 * returns false.
19 *
20 * A typical usage of an [Iterator] looks as follows:
21 *
22 * var it = obj.iterator;
23 * while (it.moveNext()) {
24 * use(it.current);
25 * }
19 */ 26 */
20 abstract class Iterator<E> { 27 abstract class Iterator<E> {
21 /** 28 /**
22 * Moves to the next element. Returns true if [current] contains the next 29 * Moves to the next element. Returns true if [current] contains the next
23 * element. Returns false, if no element was left. 30 * element. Returns false, if no element was left.
24 * 31 *
25 * It is safe to invoke [moveNext] even when the iterator is already 32 * It is safe to invoke [moveNext] even when the iterator is already
26 * positioned after the last element. In this case [moveNext] has no effect. 33 * positioned after the last element. In this case [moveNext] has no effect.
27 */ 34 */
28 bool moveNext(); 35 bool moveNext();
29 36
30 /** 37 /**
31 * Returns the current element. 38 * Returns the current element.
32 * 39 *
33 * Return [:null:] if the iterator has not yet been moved to the first 40 * Return [:null:] if the iterator has not yet been moved to the first
34 * element, or if the iterator has been moved after the last element of the 41 * element, or if the iterator has been moved after the last element of the
35 * [Iterable]. 42 * [Iterable].
36 */ 43 */
37 E get current; 44 E get current;
38 } 45 }
39
40 class HasNextIterator<E> {
41 static const int _HAS_NEXT_AND_NEXT_IN_CURRENT = 0;
42 static const int _NO_NEXT = 1;
43 static const int _NOT_MOVED_YET = 2;
44
45 Iterator _iterator;
46 int _state = _NOT_MOVED_YET;
47
48 HasNextIterator(this._iterator);
49
50 bool get hasNext {
51 if (_state == _NOT_MOVED_YET) _move();
52 return _state == _HAS_NEXT_AND_NEXT_IN_CURRENT;
53 }
54
55 E next() {
56 // Call to hasNext is necessary to make sure we are positioned at the first
57 // element when we start iterating.
58 if (!hasNext) throw new StateError("No more elements");
59 assert(_state == _HAS_NEXT_AND_NEXT_IN_CURRENT);
60 E result = _iterator.current;
61 _move();
62 return result;
63 }
64
65 void _move() {
66 if (_iterator.moveNext()) {
67 _state = _HAS_NEXT_AND_NEXT_IN_CURRENT;
68 } else {
69 _state = _NO_NEXT;
70 }
71 }
72 }
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