Extend Iterable instead of implementing it.

sdk/lib/core/iterable.dart

Index: sdk/lib/core/iterable.dart
diff --git a/sdk/lib/core/iterable.dart b/sdk/lib/core/iterable.dart
index 603a9df1a1e5ef04a740d127c4dcb83b6f97685b..538720d1399e8f1cbf4d0a12c608ca9deb4d7264 100644
--- a/sdk/lib/core/iterable.dart
+++ b/sdk/lib/core/iterable.dart
@@ -15,6 +15,8 @@
  * be used as the right-hand side of a for-in construct.
  */
 abstract class Iterable<E> {
+  const Iterable();
+
   /**
    * Returns an [Iterator] that iterates over this [Iterable] object.
    */
@@ -28,7 +30,13 @@ abstract class Iterable<E> {
    * to return a collection of the same general type as themselves.
    * E.g., [List.mappedBy] should return a [List].
    */
-  Collection mappedBy(f(E element));
+  Collection mappedBy(f(E element)) {
+    // TODO(floitsch): this is just a temporary function to provide a complete
+    // skeleton. It will be changed to become lazy soon.

[sra1, 2012/11/15 01:02:18]

How will it be lazy?

[floitsch, 2012/11/15 01:27:27]

Have a look here:
https://chromiumcodereview.appspot.com/11366111/

+    List result = new List();

[sra1, 2012/11/15 01:02:18]

Any reason to use new List() when the more concise [] means the same?

[floitsch, 2012/11/15 01:27:27]

Done.

+    for (E element in this) result.add(f(element));
+    return result;
+  }
 
   /**
    * Returns a collection with the elements of this collection
@@ -40,7 +48,13 @@ abstract class Iterable<E> {
    * An element satisfies the predicate [f] if [:f(element):]
    * returns true.
    */
-  Collection<E> where(bool f(E element));
+  Collection<E> where(bool f(E element)) {
+    // TODO(floitsch): this is just a temporary function to provide a complete
+    // skeleton. It will be changed to become lazy soon.
+    List result = new List<E>();

[sra1, 2012/11/15 01:02:18]

Ditto <E>[]

[floitsch, 2012/11/15 01:27:27]

Done.

+    for (E element in this) if (f(element)) result.add(element);
+    return result;
+  }
 
   /**
    * Check whether the collection contains an element equal to [element].