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From: dbush <dbush.mobile@gmail.com>
Newsgroups: comp.theory
Subject: Re: Every sufficiently competent C programmer knows --- Semantic
 Property reiterated
Date: Thu, 13 Mar 2025 12:12:50 -0400
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On 3/13/2025 12:09 PM, olcott wrote:
> On 3/13/2025 10:44 AM, Ben Bacarisse wrote:
>> Mike Terry <news.dead.person.stones@darjeeling.plus.com> writes:
>>
>>> On 11/03/2025 18:23, Richard Heathfield wrote:
>>>> On 11/03/2025 17:42, Mike Terry wrote:
>>>>> Finally, if you really want to see the actual HHH code, its in the
>>>>> halt7.c file (along with DDD) that PO provides links to from time to
>>>>> time.  However it's not very illuminating due to bugs/design
>>>>> errors/misunderstandings which only serve to obfuscate PO's errors in
>>>>> thinking.
>>>> [I've now seen the code. Oh deary deary me.]
>>>
>>> :)
>>>
>>>> Thank you for a spirited attempt to be cogent - or at least as 
>>>> cogent as
>>>> it is possible to be in the circumstances!
>>>> I think PO's first step must be to demonstrate that HHH() correctly
>>>> diagnoses some easy functions, such as these:
>>>
>>> Not really necessary - PO is not trying or claiming to have a (full)
>>> halt decider.
>>>
>>> Originally his claim was that he had a program which worked for the
>>> counter-example TM used in the common (e.g. Linz book) proof.
>>
>> That, of course, depends on the way the wind's blowing.  For example in
>> 2020:
>>
>>    "The non-halting decider that I defined accepts any and all
>>    non-halting inputs and rejects any and all halting inputs."
>>
>> But then he retreated to the "once case" argument again until:
>>
>> Me: "Recent posts have said that you really do claim to have a halting
>>      decider.  Have you extended your claim or was that a
>>      misunderstanding?"
>>
>> PO: "I really do have a halting decider."
>>
>>> ... Such a
>>> program is impossible, as Linz and others prove, so having a program 
>>> H and
>>> its corresponding "counter-example" D, such that H correctly decides D,
>>> would certainly show that the Linz proof is wrong.  His claim was always
>>> that he had "refuted the HP proof", or sometimes that he had refuted 
>>> the HP
>>> theorem itself although he's been told dozens of times that there are 
>>> many
>>> alternative proofs for the result.
>>
>> Way back in 2004 he was sure that:
>>
>>    "I have correctly refuted each and every mechanism by which the
>>    [halting theorem] has been proven to be true. I have not shown that
>>    solving the Halting Problem is possible, merely refuted every proof
>>    that it is impossible."
>>
>> I expect a publication anytime.  20 years is just about enough to get
>> all the details right.
>>
>>> [As it turned out, PO's D(D) halted when run under his x86utm 
>>> environment,
>>> while H(D,D) which is required to return the halting status of 
>>> computation
>>> D(D) returned 0 (=non-halting).  That is exactly what the Linz proofs
>>> claim!]
>>
>> We must always remember that PO has re-defined what it means for the
>> answer to be correct:
>>
>> Me: "Here's the key question: do you still assert that H(P,P) == false
>>      is the "correct" answer even though P(P) halts?"
>>
>> PO: "Yes that is the correct answer even though P(P) halts."
>>
>> He's been quite clear about it:
>>
>>    "When we make the single change that I suggest the halting problem
>>    ceases to be impossible to solve because this revised question is not
>>    subject to pathological self-reference."
>>
>>    "This transforms an undecidable problem into a decidable problem."
>>
>> I hope you forgive me just chipping in with stuff you know perfectly
>> well, but I thought I'd just give some background as Richard is a new
>> participant and my comments fit better with your post than his.
>>
> 
> typedef void (*ptr)();
> int HHH(ptr P);
> 
> int DD()
> {
>    int Halt_Status = HHH(DD);
>    if (Halt_Status)
>      HERE: goto HERE;
>    return Halt_Status;
> }
> 
> When N steps of DD are correctly emulated by
> any HHH then each DD cannot possibly reach
> its own final state and terminate normally.
> 
> We we recall Rice's Theorem we know that the
> issue to be decided must be based on the semantic
> property that the input finite string specifies.
> 

And the semantic property we care about, which you implicitly agreed is 
one, is the property of the directly executed DD.