Update charted to 0.4.8 and roll

packages/collection/lib/src/iterable_zip.dart

+// 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.
+
+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<T> extends IterableBase<List<T>> {
+  final Iterable<Iterable<T>> _iterables;
+
+  IterableZip(Iterable<Iterable<T>> iterables) : this._iterables = iterables;
+
+  /// Returns an iterator that combines values of the iterables' iterators
+  /// as long as they all have values.
+  Iterator<List<T>> get iterator {
+    var iterators = _iterables.map((x) => x.iterator).toList(growable: false);
+    // TODO(lrn): Return an empty iterator directly if iterators is empty?
+    return new _IteratorZip<T>(iterators);
+  }
+}
+
+class _IteratorZip<T> implements Iterator<List<T>> {
+  final List<Iterator<T>> _iterators;
+  List<T> _current;
+
+  _IteratorZip(List<Iterator<T>> 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<T> get current => _current;
+}