Re: "unspecified" and SET!

[Dorai Sitaram <titan!dorai@rice.edu>]

In article <2281@ubc-cs.UUCP> manis@grads.cs.ubc.ca (Vincent Manis) writes:
>Going to the trouble to develop a calculus of unspecified values
>strikes me as almost as silly as some of the things I did when I was
>involved in writing an Algol 68 compiler.

If this is in response to my posting(s) entitled "unspecified and
set!"  (and I'm not sure it is -- Vincent doesn't say), I request
permission to shriek, "No! This is not what I meant!" ;-)

I was drawing attention to side-effecting constructs in the literature
(that they appeared in a calculus-definition is of secondary
importance) that give all the "power" of current Schemes WITHOUT
having to mess with (returning) unspecified values at all. I do, of
course, concur with Vincent that having an unspecified object like
#!unspecified is close to being the all-time great oxymoron of our
troubled times (though he might not use the selfsame words ;-]).

Second, the comparison that Vincent draws between "(#!)unspecified"
and "bottom" is not correct. "Bottom" stands for divergence
(non-termination) and occasionally, errors; "(#!)unspecified" is a
stopgap value concocted to stand for a meaningless value returned in a
TERMINATING computation.

--dorai
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