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From: olcott <polcott333@gmail.com>
Newsgroups: comp.lang.c,comp.lang.c++
Subject: Re: Can D correctly simulated by H reach its own line 06 and halt?
Date: Tue, 21 May 2024 21:22:27 -0500
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On 5/21/2024 8:31 PM, Sam wrote:
> olcott writes:
> 
>> I learned C when K & R was the standard.
>> I met Bjarne Stroustrup are our local university when he
>> was promoting his new language. I have been a professional
>> programmer since 1984, and a professional C++ software
>> engineer since Y2K.
> 
> And I have been Lord High Posterchild Of The Known Universe, since 
> birth. So what?
> 
>>
>> I know that my C function template will not execute.
> 
> Not only that, there is no such thing as "C function template" in the 
> first place. Templates are a C++ thing. There are not templates in C.
> 
>> I can't provide the details of this because this template refers to
>> an infinite set of H/D pairs where H is only required to correctly
>> simulate N steps of D using an x86 emulator. H must be a pure function.
> 
> Unfortunately, all our psychics are out to lunch and there's noone in 
> the office who knows how to operate the magical mind ray-beam machine 
> that's needed in order to extract all the relevant details from your 
> head. You'll need to patiently wait until the lunch break is over.
> 
> We apologize for the inconvenience.
> 

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       }

It is trivial to see that for every H/D pair of the infinite
set of H/D pairs that match the above template that

D correctly correctly simulated by H cannot possibly reach
its own final state at line 06 and halt because D correctly
simulated by H remains stuck in recursive simulation.

This provides the basis for simulating termination analyzer H to
correctly determine that the halting problem's counter-example
input D cannot possibly halt.

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