On Saturday 20 July 2002 02:24 pm, Andreas Raab wrote:
> I haven't been around during the clone (err... message-eating nil)
> wars but after reading your paper it makes me wonder if anyone
> actually ever _tried_ to use a message eating nil (and not just
> reason about it) in Smalltalk.

Yes, there was at least one article that I'd read on the web from a 
Well Known Name In Smalltalk that discussed this as a good idea. 
Forget who, though. Perhaps it was Alan Wirfs-Brock? Jan Steinman?

I remember making one and using it for a while several years ago. I 
don't remember how it turned out, though.

You do have to watch out for "== nil" (and #ifNil: #ifNotNil: etc. 
that end up doing "== nil"). There's a mixture of

isNil ifTrue: (which would work, as it's a message send)
== nil ifTrue: (which wouldn't work)
ifNil: (which also wouldn't)

etc. in Squeak.

I know that Kent Beck has mentioned in some of his discussions about 
the Chrysler accounting system that using custom nil objects (i.e. 
NilEmployee) was helpful. I believe, though, that these were not 
message-eaters, but just harmless dummy objects.

-- 
Ned Konz
http://bike-nomad.com
GPG key ID: BEEA7EFE