Template parser

utils/template/utils.dart

+// Copyright (c) 2011, 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.
+
+// Collection<T> supports most of the ES 5 Array methods, but it's missing
+// map and reduce.
+
+// TODO(jmesserly): we might want a version of this that return an iterable,
+// however JS, Python and Ruby versions are all eager.
+List map(Iterable source, mapper(source)) {
+  List result = new List();
+  if (source is List) {
+    List list = source; // TODO: shouldn't need this
+    result.length = list.length;
+    for (int i = 0; i < list.length; i++) {
+      result[i] = mapper(list[i]);
+    }
+  } else {
+    for (final item in source) {
+      result.add(mapper(item));
+    }
+  }
+  return result;
+}
+
+reduce(Iterable source, callback, [initialValue]) {
+  final i = source.iterator();
+
+  var current = initialValue;
+  if (current == null && i.hasNext()) {
+    current = i.next();
+  }
+  while (i.hasNext()) {
+    current = callback(current, i.next());
+  }
+  return current;
+}
+
+List zip(Iterable left, Iterable right, mapper(left, right)) {
+  List result = new List();
+  var x = left.iterator();
+  var y = right.iterator();
+  while (x.hasNext() && y.hasNext()) {
+    result.add(mapper(x.next(), y.next()));
+  }
+  if (x.hasNext() || y.hasNext()) {
+    throw new IllegalArgumentException();
+  }
+  return result;
+}
+
+