[Types-sig] MetaClasses (Non-ASCII art)

[M.-A. Lemburg]

David Ascher wrote:
> 
> On Wed, 2 Dec 1998, Just van Rossum wrote:
> 
> > At 10:40 AM +0100 12/2/98, M.-A. Lemburg wrote:
> > >It does... also looks a lot like what I posted to the egroups
> > >list. I'll just repost it here for simplicity:
> >
> > Thanks, that is an interesting approach, which actually looks a lot like
> > the current class/type scheme...
> 
> Both of you (MAL and JvR) present schemes in which the notion of class and
> instance (and something else, call it metaclass) are reified.  This is in
> contrast, I believe, to GvR's view, which allows unlimited 'levels of
> metaness', aka turtledepth.

Can't speak for Just, but in the scheme I have in mind there
can be any number of objects between Object and the top level
objects.

I just left them out to avoid confusion (see my note at the bottom
of the drawing).
 
> This may be a good thing, or not.  I'm not sure.  Smalltalk, I believe,
> also has only three levels.  Does it make sense to have arbitrary
> turtledepth?

Well, I think practically speaking there's probably not much use
for arbitrary depth in meta-structures.

Just to clarify this a little: I'm talking about real meta levels
here not inheritance levels. Meta levels are always recursed into
while inheritance does not enforce this.

-- 
Marc-Andre Lemburg                               Y2000: 394 days left
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