Added expand method to iterables.

sdk/lib/core/iterable.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.
 
 part of dart.core;
 
 /**
  * The [Iterable] interface allows to get an [Iterator] out of an
  * [Iterable] object.
  *
@@ skipping 40 matching lines @@
   Iterable map(f(E element)) => new MappedIterable<E, dynamic>(this, f);
 
   /**
    * Deprecated alias for [map].
    *
    * @deprecated
    */
   Iterable mappedBy(f(E element)) => map(f);
 
   /**
-    * Returns a lazy [Iterable] with all elements that satisfy the
-    * predicate [f].
-    *
-    * This method returns a view of the mapped elements. As long as the
-    * returned [Iterable] is not iterated over, the supplied function [f] will
-    * not be invoked. Iterating will not cache results, and thus iterating
-    * multiple times over the the returned [Iterable] will invoke the supplied
-    * function [f] multiple times on the same element.
-    */
+   * Returns a lazy [Iterable] with all elements that satisfy the
+   * predicate [f].
+   *
+   * This method returns a view of the mapped elements. As long as the
+   * returned [Iterable] is not iterated over, the supplied function [f] will
+   * not be invoked. Iterating will not cache results, and thus iterating
+   * multiple times over the the returned [Iterable] will invoke the supplied
+   * function [f] multiple times on the same element.
+   */
   Iterable<E> where(bool f(E element)) => new WhereIterable<E>(this, f);
 
+
+  /**
+   * Expand each element of this [Iterable] into zero or more elements.
+   *
+   * The resulting Iterable will run through the elements returned
+   * by [f] for each element of this, in order.
+   *
+   * The returned [Iterable] is lazy, and will call [f] for each element
+   * of this every time it's iterated.
+   */
+  Iterable expand(Iterable f(E element)) =>
+      new ExpandIterable<E, dynamic>(this, f);
+
   /**
    * Check whether the collection contains an element equal to [element].
    */
   bool contains(E element) {
     for (E e in this) {
       if (e == element) return true;
     }
     return false;
   }
 
@@ skipping 331 matching lines @@
       _index++;
       return true;
     } else {
       _current = null;
       return false;
     }
   }
 
   E get current => _current;
 }