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// 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.
library iterable_zip;
import "dart:collection";
* 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 = => 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;