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From: Richard Damon <richard@damon-family.org>
Newsgroups: comp.theory
Subject: Re: Every sufficiently competent C programmer knows
Date: Tue, 11 Mar 2025 18:46:58 -0400
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On 3/11/25 9:26 AM, olcott wrote:
> On 3/11/2025 5:01 AM, Richard Heathfield wrote:
>> On 11/03/2025 08:55, Fred. Zwarts wrote:
>>> Op 11.mrt.2025 om 00:41 schreef olcott:
>>>> typedef void (*ptr)();
>>>> int HHH(ptr P);
>>>>
>>>> void Infinite_Loop()
>>>> {
>>>>    HERE: goto HERE;
>>>>    return;
>>>> }
>>>>
>>>> void Infinite_Recursion()
>>>> {
>>>>    Infinite_Recursion();
>>>>    return;
>>>> }
>>>>
>>>> void DDD()
>>>> {
>>>>    HHH(DDD);
>>>>    return;
>>>> }
>>>>
>>>> int DD()
>>>> {
>>>>    int Halt_Status = HHH(DD);
>>>>    if (Halt_Status)
>>>>      HERE: goto HERE;
>>>>    return Halt_Status;
>>>> }
>>>>
>>>> That when HHH correctly emulates N steps of the
>>>> above functions that none of these functions can
>>>> possibly reach their own "return" instruction
>>>> and terminate normally.
>>>> >
>>>>
>>>> Since HHH does see that same pattern that competent
>>>> C programmers see it correctly aborts its emulation
>>>> and rejects these inputs as non terminating. 
>>>
>>> All competent C programmers see that HHH correctly reports that it 
>>> cannot possibly reach the 'return' instruction.
>>
>> First, my credentials. I've been programming in C for over 35 years; 
>> I'm told that my book on C has been used on two undergraduate Comp Sci 
>> courses (one in the States and one in the UK); and I have my Knuth 
>> cheque. I don't claim to be any kind of programming guru, but I hope I 
>> do not overstate the case when I suggest that I can be regarded as 
>> competent not just as a programmer but specifically in the C language.
>>
>> And yet I can't even /see/ HHH, let alone judge what it does or does 
>> not do correctly. All I see is a call to it.
>>
> 
> It is stipulated that HHH correctly emulates N
> steps of the x86 machine code of its input functions.
> This may or may not include HHH emulating itself
> emulating an input.

And thus you have stipulated that all calls to HHH will return in finite 
time, as it only take finite time to emulate a finite number of 
instructions.

Thus HHH must, to do that, must treat the call to HHH(DD) within DD as 
returning a value, and since you claim it is correct to return 0, 
obviously that number is 0, and thus it is OBVIOUS, that DD correctly 
emulated to call an HHH(DD) that WILL return 0, must reach its final 
halting state,

If it stops before it gets there, because it only emulates N steps, that 
doesn't mean that the behavior of the input is non-halting, as that 
requires it to NEVER reach a final state no matter how long you process 
the input.

> 
>> And ld concurs. It can't see HHH either.
>>
>> I suggest that Mr Olcott should supply the missing source code if he 
>> wishes to be taken seriously.
>>
> 
> Not required for the above thought experience where
> every relevant behavior has been fully specified. This
> is merely another lame attempt on your part to perpetually
> dodge the point.
> 

THen we just need to use the fact that HHH is claimed to return the answer.

You don't seem to understand that you can't depend on the Truth Fairy.

DD, by your definitions, HALTS, it just takes longer than HHH will look, 
and thus HHH gets the wrong answer.

Since you can't show why HHH needs to get to the end in its simulation, 
you are admitting that part of the requirement is just part of your FRAUD.