X-Message-Number: 9328
Date:  Fri, 20 Mar 98 17:03:38 
From: Mike Perry <>
Subject: Re: CryoNet #9322

Thomas Donaldson writes,

>Just like a true Turing machine, the Siegelmann device is an
>intellectual construction only. Why is an infinite tape not laughable
>while use of infinite decimal numbers is?

I would say, because the "infinite tape" is not really a requirement. 
Instead you can just assume a *growing supply* of tape, i.e. make 
sure the machine has extra tape as needed, starting from some
finite base, which includes the initial inscription, assumed to be
finite, that the machine must work with. The extra tape is 
*blank* tape, which the machine may then proceed to inscribe as it 
goes about its work. The infinite decimal number is, in effect, an 
*infinitely inscribed* tape, already written, which is something else entirely.

Mike Perry

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