X-Message-Number: 9338
Subject: a reply to more boring text from Thomas Donaldson.
Date: Mon, 23 Mar 1998 12:25:02 -0500
From: "Perry E. Metzger" <>

> From: Thomas Donaldson <>
> Date: Sun, 22 Mar 1998 15:07:14 -0800 (PST)

> I am glad to be considered a Markov chain.

At last, you've shown some sign of actually having READ a message I
sent. Contgratulations.

> As for "statistical functional equivalence", IF we can simulate a human being
> without running into the chaos problem, THEN I will accept your notion of
> statistical functional equivalence.

The "statistical functional equivalence" notion explains why "chaos"
is not a problem in this sort of simulation, which is not designed to
be predictive in nature.

Did you bother to read my extensive explanation of the notion, which I 
repeated in four or five separate messages? Or do I have to repeat it again.


> My own sources do not raise the need for a stack in defining
> recursion.

Not in DEFINING. In IMPLEMENTING.

If you want to implement recursion on a machine designed the way
current computers are (and, indeed, the way any practical computer
could be designed) then you either need to use a stack, or you need to 
change the algorithm into one that is more naturally expressed in an
iterative mode. (It is trivial to do the latter with tail recurive
algorithms (do you even know what tail recursion is, Mr. Donaldson?)
but not always simple to do it for other algorithms.)

I'm still waiting for your counterexample, by the way. Its been six
days. If you knew what you were talking about, presumably you could
have shown us one by now.

> And now about Turing machines: you have agreed, yourself, that their use
> lies in showing the IMPOSSIBILITY of a computation, as distinct from its
> possibility.

So?

You were the one who brought up this notion of "neurons can do things
Turing Machines can't", not me.

> Furthermore, you are simply wrong when you claim to have solved the problem
> of a finite tape. The machine can do 4 things: halt, mark 0, mark 1, or  move
> forward or backward. To have it accept a new length of tape you must
> allow additional instructions.

Those aren't the instructions a Turing Machine takes. Were they the
instructions a Turing Machine took, and were an additional instruction 
needed (it would not be even on the machine you hypothesize), the new
machine would be mathematically provable to be Turing equivalent.

In other words, you're boring, Mr. Donaldson.

> I am sure that you can devise a suitable model here, though it will most
> certainly lack the simple beauty of a true Turing machine.

You don't even understand true Turing Machines. No one ever said they
take only "0"s and "1"s in their input or output language. In fact,
I've never seen them defined that way, for example. Saying they would
hang on the right as well as on the left would not be any sort of
"inelegance", and if it were, what would it matter?

Perry

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