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From: stephen@estragon.uchicago.edu (Stephen P Spackman)
Newsgroups: comp.lang.misc
Subject: Re: Halting Problem Solved! Film at 11! (Was Re:
Message-ID: <STEPHEN.91May9022258@estragon.uchicago.edu>
Date: 9 May 91 08:22:58 GMT
References: <2953@optima.cs.arizona.edu>
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In-Reply-To: gudeman@cs.arizona.edu's message of 8 May 91 17: 56:03 GMT

In article <2953@optima.cs.arizona.edu> gudeman@cs.arizona.edu (David Gudeman) writes:
|In article  <STEPHEN.91May7205714@pesto.uchicago.edu> Stephen P Spackman writes:
|]In article <2861@optima.cs.arizona.edu> gudeman@cs.arizona.edu (David Gudeman) writes:
|]
|]|If you want to get theoretical, then you can _theoretically_ keep
|]|buying tapes...
|]
|]There is definitely and without question a finite amount of matter in
|]the universe that I am willing to make tapes out of.
|]
|]Evidently, I disagree. I am PERSONALLY willing to engineer my
|]compilers on the assumption that (a) FTL travel, (b) many-worlds
|]parallelism and (c) anything comparably revolutionary will not become
|]available within the useful lifetime of the software.
|
|Not fair, Stephen.  You took the theoretical argument and made
|practical objections to it.  Your objections do not address the issue
|of whether a computer is _theoretically_ a finite state machine -- and
|I covered the practical issues in the part you did not cite.

I wasn't cheating, I was just trying to reiterate - and defend - a
particular cut on the problem. There was a particular view given here
that it is interesting to study the THEORETICAL properties of
PRACTICAL machines.  I *could* talk about the theoretical properties
of theoretical machines or about the practical properties of practical
machines, yes, and that would be "fairer pool" in that it would
address what, perhaps, you thought I was talking about. But I
disagree!

The point is: bar some MAJOR breakthroughs in physics, the machines we
WORK with have limits. The fact that machines have limits has
potential theoretical implications. It is proposed by some to explore
them.

Objections that theoretical machines lack practical limits or that the
practical limits of practical machines are more immediate are SIMPLY
NOT GERMANE.

I addressed your comment that I understood to address my argument.

Let me try one more time. PRACTICAL computers are FSMs and not fully
general turing machines because PRACTICAL computers are finite. The
fact that PRACTICAL computers are finite is an important THEORETICAL
property of PRACTICAL computers and may need to be addressed before
certain ideas are dismissed. And this is true even if you include all
the input they're ever going to get as state space.

...I feel a bit like you're telling me that it's impossible to code a
correct sort, because you never know when your input is going to be
an infinite stream and the function just might not terminate....
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stephen p spackman         Center for Information and Language Studies
systems analyst                                  University of Chicago
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