On Wednesday, August 21, 2002, at 11:03 PM, Richard A. O'Keefe wrote:

> Ralph Johnson <johnson at cs.uiuc.edu> wrote:
> 	But I think your "dead simple" fix is a horrible hack.
>
> It is a principled technique of general utility:
>  whenever you are about to do incompatible things to one object,
>  do one of those things to a copy instead.

I don't know about this Richard.  #removeAll: implies certain 
side-effects with respect to the receiver that render its meaningful 
definition undefined when the parameter is modified during its 
operation.  By extending the defined range of #removeAll: for some, but 
not all parameters that are modified during its operation, we invite a 
more specific definition of the selector, perhaps:
	#removeAllExceptWhenParameterIsEquivalentToReceiverInWhichCaseJustUseACopyButStillStayUndefinedForOtherCasesWhereTheParameterIsModifiedDuringExecution:

This suggests to me that the ugly hack characterization isn't entirely 
off-base.