Re: "unspecified" and SET!

[Vincent Manis <att!alberta!ubc-cs!grads.cs.ubc.ca!manis@bloom-beacon.mit.edu>]

In article <81872@ti-csl.csc.ti.com> gateley@m2.UUCP (John Gateley) writes:
>Do you mean Matthias Felleisen's calculus for Scheme? It is neither a 
>calculus of unspecified values nor silly. It is a better theoretical
>basis for Scheme than the lambda value calculus: it includes both
>set! style side effects and continuations in its equations.

To clarify, let me say emphatically that I *don't* mean Felleisen's
calculus. As John says, Felleisen's work is not at all silly. I was
instead referring to the proposals for #!unspecified, which, is either
the same as `bottom' in denotational semantics or it is not. In the
former case, #!unspecified should be returned, also, in both a
division by 0 and a non-terminating recursion. In the latter case,
#!unspecified is somewhat pointless (set! could just as easily return
`()), unless one has some reason for distinguishing the two.

While I do not care for William of Ockham's metaphysics, there is much
to say for his Razor. 

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