[self-interest] Re: Nil

Randy Smith Randall.Smith at Eng.Sun.COM
Wed Jul 7 16:46:56 UTC 1999


Douglas, I think you get the basic idea, and your own refinement of
having a common nil-like parent is kind of interesting. Though the
behavior shared by these "not yet specified" or nil-like objects is
curiously hard to articulate. I mean, what is the essence of vagueness?

If you can come up with something, implement it, use it, and extract a
lesson or two, it might be an interesting OOPSLA paper.

(In my opinion!)

	--Randy

> 
> Remember that discussion on the usefulness of nil and the default
> initialization of slots? I was reading the Self 4.0 Programmer´s
> Reference Manual this weekend and thought a little bit more about the
> purpose of nil. If I got the idea, nil should not be used as a default
> initializer, instead a specific object should be created to mean "no
> object here" in the particular context. Well, perhaps (I don't remember
> if anyone said this) nil could be used as a prototype of this kind of
> object, or a traits, so that the common behavior of all "null" objects
> would be concentrated on it.
> Is it already so?
> I understand that nil is one object, and as such it has one type. So if
> one uses it to represent "no object" in places where different types are
> being represented, then one is losing type information. If we create
> other objects to play this role, so that nil is their parent, or so that
> they are cloned from nil, perhaps we can keep the commonality of the nil
> "family" and also keep different nil's for different "types".
> Did I get the idea, folks?
> Do I make a point?
> 
> Douglas
> 
> 
> 
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