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Re: "unspecified" and SET!
In article <firstname.lastname@example.org> 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.
____________ Vincent Manis | email@example.com
___ \ _____ The Invisible City of Kitezh | firstname.lastname@example.org
____ \ ____ Department of Computer Science | email@example.com
___ /\ ___ University of British Columbia | uunet!ubc-cs!manis
__ / \ __ Vancouver, BC, Canada V6T 1W5 | (604) 228-2394
_ / __ \ _ "Theoretical computer science helps me convince people that
____________ my indecisiveness is really Nondeterminism, which sounds like
a much more positive characteristic." -- a student