On 4/9/2012 21:14, nemesis wrote:
> Em 09/04/2012 02:39, Darren New escreveu:
>> We're confusing two things here. One is that real computers can perform
>> computations that TMs can't, because TM's don't have cameras,
>> microphones, etc.
>
> Those are still tapes, minus time.

No, they're really not. They're (possibly) isomorphic to a tape, but they're 
not tape. That's my point.

 > If you recorded all user input from any
> device and fed it to a TM,

... you would need to use something other than a TM to do that.

> it'd still work the same.

For *some* meaning of "work." Certainly if you tried to do that with (say) 
google's self-driving automobile, you'd be in trouble if the computer in the 
car didn't have a connection to the laser eye thing.

>> One TM can't program another TM at all, because a TM
>> can only write to its own tape.
>
> I'm not sure I'm following,

I don't know how else to say it. If you have two turing machines sitting 
next to each other in a room, the one can't program the other. By 
definition, the I/O of a turing machine is too limited to allow that. The 
output of one machine is not suitable as the program for the other machine.

It's really not all that deep. I just found it amusing when made 
self-referential.

-- 
Darren New, San Diego CA, USA (PST)
   "Oh no! We're out of code juice!"
   "Don't panic. There's beans and filters
    in the cabinet."

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