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Re: Need help with Class-Allocated Slots

Andreas Bogk <andreas@andreas.org> wrote:
> "Scott McKay" <swm@mediaone.net> writes:
> 
> > During the design of Dylan, I proposed that class slots be accessible
> > by calling the accessor on the class object itself, but Moon didn't like
> > it because it confuses class vs. instance.  I agree with Moon on the
> > exact point, but I still think that the semantics of my dumb-ass proposal
> > are well enough understood, that it is probably reasonable.
> 
> Maybe it's time to resurrect the Dylan Language discussion at
> 
> http://www.isr.com/dylan/dylan-language/
> 
> I agree that it should be possible to access class slots without
> having an instance.

The big problems with this that is it's hard to know what to do if
there is a specialized method shadowing the basic getter. For example:

  define class <super> (<object>)
     class slot foo :: <integer>,
       init-value: 6;
  end class;

  define class <perverse-subclass> (<super>)
    slot bar :: <integer>,
      init-value: 24;
  end class;

  define method foo (obj :: <perverse-subclass>, #next next-method)
    obj.bar * next-method()
  end method;

Then it's totally unclear what you should return with a method like

  class-slot(class, getter-generic)

when you call class-slot(<perverse-subclass>, foo). IMO, in this case,
half a loaf is definitely worse than either no loaf. 


Neel
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