On the theory that there are no dumb questions -- and given my 
experience that you men and women frequently take my breath with the 
elegance of your solutions to my dumb questions:

In the silly Smalltalk tricks category, is there a "least ugly" way 
to generate a comma separated list out of a collection?  The pithy:

	aCollection do:
		[:each |
		 each printOn: aStream.
		 aStream nextPut: $,]

is of course flawed because it prints an extra comma at the end of 
the collection.  Assuming a SquenceableCollection,

	aCollection allButLast do:
		[:each |
		 each printOn: aStream.
		 aStream nextPut: $,].
	aCollection last printOn: aStream

works, but (i) croaks on empty collections, (ii) unnecessarily copies 
nearly the entire collection and (iii) offends my eyes.  Other 
approaches seemed even uglier to me.

	s _ Stream on: aCollection.
	[s atEnd] whileFalse:
		[s next printOn: aStream.
		 s atEnd ifFalse: [aStream nextPut: $,]]

seemed less inelegant, albeit a bit busy and heavy-handed.

Of course, I can bury any ugliness, if necessary, just by adding a 
#do:inbetween: method or the like to the Collection protocol.  Is 
that reason enough to change a core system class?  Am I too shy about 
that sort of thing?

Assume you have an application where you must be doing this sort of 
thing a lot.  Is there a preferred approach or idiom for this kind of 
enumeration?