Charles,

Maybe I am looking at interfaces from the wrong angle. I see an Interface as
a kind of contract. If an Object implements an interface, you can make lots
of otherwise dangerous assumptions about what messages it understands.
Similar to IDL or Types (I know, that word makes Smalltalkers cringe). If
Distributed Objects are to be the next big thing, how will you talk to them?
Discovering an Interface is a good way. As I have explained, the current
Interfaces are 'leaky' in that an Object can have Interface A, you can send
it an Interface A message, but the object will not understand it. I gave an
example of this in my previous post -

>>To truly reason
>>about Interfaces it is not enough to treat them as a bunch of selectors.
To
>>me, the function of an Interface is as a prerequisite for communcation
>>between objects. In its present form, objects with compatible interfaces
may
>>NOT be able to communicate.
>>
>>For example, the interfaces
>>1: do: [^1]
>>2: do: [: aNumber | ^aNumber printString]
>>
>>Are incompatible and most definitely not interchangeable. However, they
are declared to be compatible with the present Interfaces approach.


>Would you mind explaining what the real practical benefits of incorporating
>something as you suggest into
>Smalltalk ?


Well, I am assuming that when you say an object implements an Interface,
that I can send it any message in that interface. Is this assumption flawed?
You will not be able to build very complex stuff without this foundation in
place. With the present Interfaces, this assumption does not work.

>Will not the addition of complexity outweigh the benefits in this case?


To be honest, I havent played around with Interfaces to determine how
difficult this is. Once the primitive classes have well-defined interfaces
it may not be as bad as it looks.

>Being aware of "interfaces" from a design perspective is important of
>course but I'm still not sold on the usefulness of enforcing them as an
>actual language construct.


How can you make a safe design if there is no guarantee that objects
implementing the interfaces can actually communicate with each other?

>SmallInterfaces as currently implemented provide a certain utility. To take
>this further as you suggest would over constrain things from my
perspective.


I think Interfaces could be hugely useful in interfacing to the outside
world. This includes compiling to C, C++, Objective C and back, implementing
IDL, communication objects across the net, etc. However, you may find that
you are getting 80% of the functionality with 20% of the complexity, which
seems like a reasonable tradeoff.

Peter