Andrew,

Proxies don't subclass UndefinedObject, they
subclass nil, much like how Object subclasses nil.

i.e.

nil subclass: #Object [...]
nil subclass: #ObjectTracer [...]
nil subclass: #Proxy [...]


Ranjan 
--- "Andrew P. Black" <black at cse.ogi.edu> wrote:
> At 14:22 -0500 2000.2.28, Norton, Chris wrote:
> >In addition to the other fine responses to your
> question (ProtoObject is the
> >superclass of Object, et. al), I believe that
> people also define Proxy
> >objects by subclassing nil (UndefinedObject),
> rather than Object.  Proxy
> >objects are common ...
> 
> 
> Unfortunately, since UndefinedObject is itself a
> subclass of Object, 
> making Proxy a subclass of UndefinedObject does not
> achieve the 
> desired effect.  (It does achieve one _undesired_
> effect -- making 
> all the Proxy objects print as nil!
> 
> I believe that the reasons for the creation of
> ProtoObject include 
> the need to have a place to put Proxy objects that
> is not a subclass 
> of Object.  ObjectOut and ImageSegmentRootStub are
> two proxy objects 
> in the image that are subclsses of ProxyObject. 
> Marcel's Trampoline 
> code should probably be modified so that Trampoline
> is a subclass of 
> ProtoObject rather than UndefinedObject.
> 
> 
> 
> 
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