Re: How to write a self-referencial TM?

On Wed, 2025-05-14 at 18:49 +0100, Richard Heathfield wrote:

On 14/05/2025 18:33, wij wrote:

On Wed, 2025-05-14 at 18:14 +0100, Richard Heathfield wrote:

On 14/05/2025 17:43, wij wrote:

On Wed, 2025-05-14 at 09:51 -0500, olcott wrote:

 
<snip>
 

 

To make a TM that references itself the closest
thing is a UTM that simulates its own TM source-code.

 
How does a UTM simulate its own TM source-code?

 
It doesn't have to simulate anything. All it has to do is to
restore the state into which the programmer wishes to recurse.

 
So, when you say "A UTM simulates X", it means 'the UTM' doesn't have to do
anything. So, 'UTM' is human (e.g. you), not a real TM?

 
No, it doesn't mean that.

You said "It doesn't have to simulate anything. All it has to do is to
restore the state into which the programmer wishes to recurse."

Then, what is it?

 

I've already shown how this can be done.

 
Where?
 

Message-ID: <1001bmf$2ao7o$2@dont-email.me>
 
Here's the gist of that article...
 
Here's the tape:
[0]
 
current state: 0
content of the square being scanned: 0
new content of the square: 0
move left, right, or stay: stay
next state: 0
 
This TM functions by returning the state of the machine to its
starting state.
 
The only functional difference between this code and yours is
that yours will blow the stack. (Mine doesn't have a stack to blow.)
 

1. Apparently your TM (one single symbol '0') is not what you say.
2. D() should have at least one final state