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From: Alan Mackenzie <acm@muc.de>
Newsgroups: comp.theory,sci.logic
Subject: Re: D correctly simulated by pure function H cannot possibly reach its, own line 06
Followup-To: comp.theory
Date: Sat, 25 May 2024 21:09:27 -0000 (UTC)
Organization: muc.de e.V.
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[ Followup-To: set ]

In comp.theory olcott <polcott333@gmail.com> wrote:

[ .... ]

> Not at all. I simply utterly reject the dishonest dodge
> of the strawman deception change-the-subject rebuttal.

> typedef int (*ptr)();  // ptr is pointer to int function in C
> 00       int H(ptr p, ptr i);
> 01       int D(ptr p)
> 02       {
> 03         int Halt_Status = H(p, p);
> 04         if (Halt_Status)
> 05           HERE: goto HERE;
> 06         return Halt_Status;
> 07       }
> 08
> 09       int main()
> 10       {
> 11         H(D,D);
> 12         return 0;
> 13       }

> The above template refers to an infinite set of H/D pairs where D is
> correctly simulated by pure function H. This was done because many
> reviewers used the shell game ploy to endlessly switch which H/D pair
> was being referred to.

> *Correct Simulation Defined*
>    This is provided because many reviewers had a different notion of
>    correct simulation that diverges from this notion.

>    A simulator is an x86 emulator that correctly emulates at least one
>    of the x86 instructions of D in the order specified by the x86
>    instructions of D.

Having simulated at least one x86 instruction, what does a correct
simulator then do?  This isn't made clear.  I'm assuming it must return
an integer, as its C specification says.

>    This may include correctly emulating the x86 instructions of H in the
>    order specified by the x86 instructions of H thus calling H(D,D) in
>    recursive simulation.

> *Execution Trace*
> Line 11: main() invokes H(D,D); H(D,D) simulates lines 01, 02, and 03 of
> D. This invokes H(D,D) again to repeat the process in endless recursive
> simulation.

Not if the simulation is "correct"; suppose the simulation emulates just
one instruction of D.  Supposing it then returns 0 (somewhat extending
your definition of a "correct simulator").  The execution trace will then
be somewhat different from what you've outlined above.

> -- 
> Copyright 2024 Olcott "Talent hits a target no one else can hit; Genius
> hits a target no one else can see." Arthur Schopenhauer

-- 
Alan Mackenzie (Nuremberg, Germany).