| // Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| /** |
| * Zipping multiple iterables into one iterable of tuples of values. |
| */ |
| library dart.pkg.collection.iterable_zip; |
| |
| import "dart:collection" show IterableBase; |
| |
| /** |
| * Iterable that iterates over lists of values from other iterables. |
| * |
| * When [iterator] is read, an [Iterator] is created for each [Iterable] in |
| * the [Iterable] passed to the constructor. |
| * |
| * As long as all these iterators have a next value, those next values are |
| * combined into a single list, which becomes the next value of this |
| * [Iterable]'s [Iterator]. As soon as any of the iterators run out, |
| * the zipped iterator also stops. |
| */ |
| class IterableZip extends IterableBase<List> { |
| final Iterable<Iterable> _iterables; |
| IterableZip(Iterable<Iterable> iterables) |
| : this._iterables = iterables; |
| |
| /** |
| * Returns an iterator that combines values of the iterables' iterators |
| * as long as they all have values. |
| */ |
| Iterator<List> get iterator { |
| List iterators = _iterables.map((x) => x.iterator).toList(growable: false); |
| // TODO(lrn): Return an empty iterator directly if iterators is empty? |
| return new _IteratorZip(iterators); |
| } |
| } |
| |
| class _IteratorZip implements Iterator<List> { |
| final List<Iterator> _iterators; |
| List _current; |
| _IteratorZip(List iterators) : _iterators = iterators; |
| bool moveNext() { |
| if (_iterators.isEmpty) return false; |
| for (int i = 0; i < _iterators.length; i++) { |
| if (!_iterators[i].moveNext()) { |
| _current = null; |
| return false; |
| } |
| } |
| _current = new List(_iterators.length); |
| for (int i = 0; i < _iterators.length; i++) { |
| _current[i] = _iterators[i].current; |
| } |
| return true; |
| } |
| |
| List get current => _current; |
| } |