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From: wij <wyniijj5@gmail.com>
Newsgroups: comp.theory
Subject: Re: How to write a self-referencial TM?
Date: Fri, 16 May 2025 02:49:45 +0800
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On Thu, 2025-05-15 at 17:08 +0100, Mike Terry wrote:
> On 14/05/2025 18:53, wij wrote:
> > On Wed, 2025-05-14 at 12:24 -0500, olcott wrote:
> > > On 5/14/2025 11:43 AM, 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):
> > > > > >=20
> > > > > > void D() {
> > > > > > =C2=A0=C2=A0=C2=A0 D();
> > > > > > }
> > > > > >=20
> > > > > > Easy?
> > > > > >=20
> > > > > >=20
> > > > >=20
> > > > > That is not a TM.
> > > >=20
> > > > It is a C program that exists. Therefore, there must be a equivalen=
t TM.
> > > >=20
> > > > > To make a TM that references itself the closest
> > > > > thing is a UTM that simulates its own TM source-code.
> > > >=20
> > > > How does a UTM simulate its own TM source-code?
> > > >=20
> > >=20
> > > You run a UTM that has its own source-code on its tape.
> >=20
> > What is exactly the source-code on its tape?
> >=20
>=20
> Every UTM has some scheme which can be applied to a (TM & input tape) tha=
t is to be simulated.=C2=A0 The=20
> scheme says how to turn the (TM + input tape) into a string of symbols th=
at represent that=20
> computation.
>=20
> So to answer your question, the "source-code on its tape" is the result o=
f applying the UTM's=20
> particular scheme to the combination (UTM, input tape) that is to be simu=
lated.
>=20
> If you're looking for the exact string symbols, obviously you would need =
to specify the exact UTM=20
> being used, because every UTM will have a different answer to your questi=
on.
>=20
>=20
> Mike.

People used to say UTM can simulate all TM. I was questing such a UTM.
Because you said "Every UTM ...", so what is the source of such UTM?