Add Set.union, Set.difference. Change Set methods to expect Set.

sdk/lib/core/set.dart

Index: sdk/lib/core/set.dart
diff --git a/sdk/lib/core/set.dart b/sdk/lib/core/set.dart
index 7977986f268daacd668dc68900453dc640f1c079..1d221a55b8d3a5f8ec986a25382da3ca2082d0cb 100644
--- a/sdk/lib/core/set.dart
+++ b/sdk/lib/core/set.dart
@@ -35,22 +35,31 @@ abstract class Set<E> extends Collection<E> {
   bool remove(Object value);
 
   /**
-   * Returns true if [collection] contains all the elements of this
-   * collection.
+   * Returns true if [other] contains all the elements of this Set.
    */
-  bool isSubsetOf(Collection<E> collection);
+  bool isSubsetOf(Set<E> other);
 
   /**
-   * Returns true if this collection contains all the elements of
-   * [collection].
+   * Returns true if this Set contains all the elements of

[floitsch, 2013/03/12 16:25:00]

Fits on one line.

[Lasse Reichstein Nielsen, 2013/03/13 13:01:42]

Done.

+   * [other].
    */
-  bool containsAll(Collection<E> collection);
+  bool containsAll(Set<E> other);
 
   /**
    * Returns a new set which is the intersection between this set and

[floitsch, 2013/03/12 16:25:00]

ditto.

[Lasse Reichstein Nielsen, 2013/03/13 13:01:42]

Done.

[Lasse Reichstein Nielsen, 2013/03/13 13:01:42]

Done.

-   * the given collection.
+   * [other].
    */
-  Set<E> intersection(Collection<E> other);
+  Set<E> intersection(Set<E> other);
+
+  /**
+   * Returns a new set which contains all the elements of this set and [other].
+   */
+  Set<E> union(Set<E> other);
+
+  /**
+   * Returns a new set with the the elements of this that are not in [other].
+   */
+  Set<E> difference(Set<E> other);
 
   /**
    * Removes all elements in the set.