Okay, the discussion is driving me mad.  Here's a set that can hold nil
in it.  I have not figured out how to juggle around and get it installed
as the system Set class, but this may be an interesting starting point
for anyone who does want to try.

"Change Set:		setsWithNil-ls
Date:			13 August 2004
Author:			Lex Spoon

A simple subclass of Set that can hold nil"
-------------- next part --------------
A non-text attachment was scrubbed...
Name: setsWithNil-ls.cs.gz
Type: application/octet-stream
Size: 1489 bytes
Desc: not available
Url : http://lists.squeakfoundation.org/pipermail/squeak-dev/attachments/20040813/7f30734c/setsWithNil-ls.cs.obj