--- a/Set.st	Tue Mar 21 11:52:48 2000 +0100
+++ b/Set.st	Tue Mar 21 11:55:06 2000 +0100
@@ -852,6 +852,27 @@
     ].
 ! !
 
+!Set methodsFor:'set operations'!
+
+- aCollection
+    "return a new set containing all elements of the receiver, which are
+     NOT also contained in the argument collection"
+
+    |newCollection|
+
+    newCollection := self species new.
+    self do:[:element |
+        (aCollection includes:element) ifFalse:[
+            newCollection add:element
+        ]
+    ].
+    ^ newCollection
+
+    "
+     #(0 1 2 3 4 5 6 7 8 9) asSet - #(1 2 3)   
+    "
+! !
+
 !Set methodsFor:'testing'!
 
 capacity 
@@ -957,6 +978,6 @@
 !Set class methodsFor:'documentation'!
 
 version
-    ^ '$Header: /cvs/stx/stx/libbasic/Set.st,v 1.61 2000-02-23 22:56:45 cg Exp $'
+    ^ '$Header: /cvs/stx/stx/libbasic/Set.st,v 1.62 2000-03-21 10:55:06 cg Exp $'
 ! !
 Set initialize!