Richard, please don't start with the name calling (re: "This is a
slander.").  None of my replies were intended to put you down or malign you
in any way.  I am only opposed to the copying that can be plainly seen in
your method (below).  I don't *know* what kind of penalties that that
innocent looking #copy will result in.  And, as I've said before, I would
prefer to retain the identity of method argument.

!Collection methodsFor: 'removing' stamp: 'raok 8/21/2002 10:45'!
removeAll: aCollection 
	"Remove each element of aCollection from the receiver. If successful
for 
	each, answer aCollection. Otherwise create an error notification.
In the
	rare case that aCollection == self, a copy of aCollection is
returned.
	ArrayedCollections cannot respond to this message."
	|c|
	(c _ aCollection) == self ifTrue: [c _ c copy].
	c do: [:each | self remove: each].
	^c! !

In an effort to remain on a constructive plain, I'd like to promote Stephan
Rudlof's implementation suggestion; it looks very promising to me.

Collection>>removeAll: aCollection
  self isEmpty
    ifFalse: [self assert: [self ~~ aCollection].
             aCollection do: [:each | self remove: each]].
  ^aCollection

In his implementation, he retains the original functionality and he adds a
warning.  Without actually trying it, the code looks good to me.

I hope y'all have a nice weekend.

---==> Chris