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Side by Side Diff: sdk/lib/collection/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
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.
4
5 part of dart.collection;
6
7 /**
8 * The [HasNextIterator] class wraps an [Iterator] and provides methods to
9 * iterate over an object using `hasNext` and `next`.
10 *
11 * An [HasNextIterator] does not implement the [Iterator] interface.
12 */
13 class HasNextIterator<E> {
14 static const int _HAS_NEXT_AND_NEXT_IN_CURRENT = 0;
15 static const int _NO_NEXT = 1;
16 static const int _NOT_MOVED_YET = 2;
17
18 Iterator _iterator;
19 int _state = _NOT_MOVED_YET;
20
21 HasNextIterator(this._iterator);
22
23 bool get hasNext {
24 if (_state == _NOT_MOVED_YET) _move();
25 return _state == _HAS_NEXT_AND_NEXT_IN_CURRENT;
26 }
27
28 E next() {
29 // Call to hasNext is necessary to make sure we are positioned at the first
30 // element when we start iterating.
31 if (!hasNext) throw new StateError("No more elements");
32 assert(_state == _HAS_NEXT_AND_NEXT_IN_CURRENT);
33 E result = _iterator.current;
34 _move();
35 return result;
36 }
37
38 void _move() {
39 if (_iterator.moveNext()) {
40 _state = _HAS_NEXT_AND_NEXT_IN_CURRENT;
41 } else {
42 _state = _NO_NEXT;
43 }
44 }
45 }
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