Darren New schrieb:
> clipka wrote:
>> Note that I'm interpreting the grammatical construct "unbounded memory 
>> tape" to read "unbounded thing called a memory tape", not "tape 
>> constituting an unbounded [amount of] memory"; your interpretation may 
>> differ.
> 
> Given the mathematical definition of the memory tape in a TM, this 
> interpretation makes no sense. Everyone says "unbounded tape" because 
> that implies "unbounded amount of storage" given how the tape is 
> defined. (I.e., it's defined as having one end as well as operations to 
> move left and right.)

Erm... do you /really/ know what you're talking about?

Whenever a Turing machine's tape is defined as having /any/ end at all, 
then it is defined as having /two/ ends, /both/ of which will be 
automatically extended as needed.

But I prefer to stick to Turing's own description:

"...an infinite memory capacity obtained in the form of an /infinite 
tape/..." (Turing 1948, p. 61)


There. Emphasis added. Any further questions?


(Yes, there /are/ variations on the theme that use a tape which is 
bounded in /one/ direction only; these are, however, not classic generic 
Turing machines.)

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