Dear Squeakers,
(sorry for cross-posting; already posted to comp.lang.smalltalk)
For a piece of research I am currently working on, I have been
reviewing the arsenal of publications on the genealogy of Smalltalk(s)
for some hints on the origin of the
Smalltalk-specific "subclass responsibility" approach, i.e. the
Smalltalk dialect for "abstract object-classes",
roughly speaking. I am particularly interested in references to design
decisions. It would be particularly enlightening to know
whether the Xerox crew was aware of the "virtual quantity" feature
introduced in Simula-67 and their perception (beyond the mere difference
with respect to type checking). I do have thoroughly
studied "original" Smalltalk-related contributions, far beyond the
Blue Book, but could not find explicit references beyond the mere fact
that this is the Smalltalk way of doing it; but why?
Note that I am well aware of more recent discussions on that very
matter, especially in your community on the semantic consistency of
subclassResponsibility:
http://wiki.squeak.org/squeak/472I am also aware of other language families that approach the idea of
deferred-required implementation by means of a /placebo/ (what I would
call it as a strategy).
Over at comp.lang.smalltalk, I was given as part of a more thorough answer:
> Because we also need a way to respond
> for the general case of a message received
> that is not understood.
So, abstract super-classes are considered a special case deriving
from a more general issue.
Is anybody aware of some nuggets out there? I would be grateful for
any hint + your thoughts when looking at your languages' history ...
Best,
//stefan
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