Re: D correctly simulated by pure function H cannot possibly reach its, own line 06

On 5/25/2024 4:09 PM, Alan Mackenzie wrote:

[ 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.
 

D correctly simulated by pure function H means that H correctly emulates
1 to N of the machine language instructions of D with an x86 emulator
and this involves 0 to M recursive emulations of H emulating itself
emulating D.
Because H is a pure function we know that H halts and returns some
value. For simplicity we will say that this value is the meaningless 56.

    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.
 

I rephrased it to be more clear.
Thanks for your review.

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

 

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