Re: How to write a self-referencial TM?

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:

On 5/14/2025 12:13 AM, wij wrote:

Q: Write a turing machine that performs D function (which calls itself):
 
void D() {
   D();
}
 
Easy?
 
 

 
That is not a TM.

 
It is a C program that exists. Therefore, there must be a equivalent TM..
 

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?

I've already shown how this can be done.

Where?