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From: Mikko <mikko.levanto@iki.fi>
Newsgroups: comp.theory
Subject: Re: How do computations actually work?
Date: Tue, 27 May 2025 11:31:37 +0300
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On 2025-05-26 16:26:47 +0000, olcott said:

> On 5/26/2025 11:05 AM, Fred. Zwarts wrote:
>> Op 26.mei.2025 om 17:50 schreef olcott:
>>> On 5/26/2025 3:38 AM, Mikko wrote:
>>>> On 2025-05-25 14:50:58 +0000, olcott said:
>>>> 
>>>>> On 5/25/2025 4:09 AM, Mikko wrote:
>>>>>> On 2025-05-24 15:25:21 +0000, olcott said:
>>>>>> 
>>>>>>> On 5/24/2025 2:54 AM, Mikko wrote:
>>>>>>>> On 2025-05-23 16:04:49 +0000, olcott said:
>>>>>>>> 
>>>>>>>>> On 5/23/2025 2:09 AM, Mikko wrote:
>>>>>>>>>> On 2025-05-23 02:47:40 +0000, olcott said:
>>>>>>>>>> 
>>>>>>>>>>> On 5/22/2025 8:24 PM, Mike Terry wrote:
>>>>>>>>>>>> On 22/05/2025 06:41, Richard Heathfield wrote:
>>>>>>>>>>>>> On 22/05/2025 06:23, Keith Thompson wrote:
>>>>>>>>>>>>>> Richard Heathfield <rjh@cpax.org.uk> writes:
>>>>>>>>>>>>>>> On 22/05/2025 00:14, olcott wrote:
>>>>>>>>>>>>>>>> On 5/21/2025 6:11 PM, Richard Heathfield wrote:
>>>>>>>>>>>>>> [...]
>>>>>>>>>>>>>>>>> Turing proved that what you're asking is impossible.
>>>>>>>>>>>>>>>>> 
>>>>>>>>>>>>>>>> That is not what he proved.
>>>>>>>>>>>>>>> 
>>>>>>>>>>>>>>> Then you'll be able to write a universal termination analyser that can
>>>>>>>>>>>>>>> correctly report for any program and any input whether it halts. Good
>>>>>>>>>>>>>>> luck with that.
>>>>>>>>>>>>>> 
>>>>>>>>>>>>>> Not necessarily.
>>>>>>>>>>>>> 
>>>>>>>>>>>>> Of course not. But I'm just reflecting. He seemed to think that my 
>>>>>>>>>>>>> inability to write the kind of program Turing envisaged (an inability 
>>>>>>>>>>>>> that I readily concede) is evidence for his argument. Well, what's 
>>>>>>>>>>>>> sauce for the goose is sauce for the gander.
>>>>>>>>>>>>> 
>>>>>>>>>>>>>> Even if olcott had refuted the proofs of the
>>>>>>>>>>>>>> insolvability of the Halting Problem -- or even if he had proved
>>>>>>>>>>>>>> that a universal halt decider is possible
>>>>>>>>>>>>> 
>>>>>>>>>>>>> And we both know what we both think of that idea.
>>>>>>>>>>>>> 
>>>>>>>>>>>>>> -- that doesn't imply
>>>>>>>>>>>>>> that he or anyone else would be able to write one.
>>>>>>>>>>>>> 
>>>>>>>>>>>>> Indeed.
>>>>>>>>>>>>> 
>>>>>>>>>>>>>> I've never been entirely clear on what olcott is claiming.
>>>>>>>>>>>>> 
>>>>>>>>>>>>> Nor I. Mike Terry seems to have a pretty good handle on it, but no 
>>>>>>>>>>>>> matter how clearly he explains it to me my eyes glaze over and I start 
>>>>>>>>>>>>> to snore.
>>>>>>>>>>>> 
>>>>>>>>>>>> Hey, it's the way I tell 'em!
>>>>>>>>>>>> 
>>>>>>>>>>>> Here's what the tabloids might have said about it, if it had made the 
>>>>>>>>>>>> front pages when the story broke:
>>>>>>>>>>>> 
>>>>>>>>>>>>   COMPUTER BOFFIN IS TURING IN HIS GRAVE!
>>>>>>>>>>>> 
>>>>>>>>>>>>   An Internet crank claims to have refuted Linz HP proof by creating a
>>>>>>>>>>>>   Halt Decider that CORRECTLY decides its own "impossible input"!
>>>>>>>>>>>>   The computing world is underwhelmed.
>>>>>>>>>>>> 
>>>>>>>>>>>> Better?  (Appologies for the headline, it's the best I could come up with.)
>>>>>>>>>>>> 
>>>>>>>>>>>> Mike.
>>>>>>>>>>>> 
>>>>>>>>>>> 
>>>>>>>>>>> There is a key detail about ALL of these proofs
>>>>>>>>>>> that no one has paid attention to for 90 years.
>>>>>>>>>>> 
>>>>>>>>>>> It is impossible to define *AN INPUT* to HHH that
>>>>>>>>>>> does the opposite of whatever value that HHH returns.
>>>>>>>>>> 
>>>>>>>>>> That is a key detail about HHH. Your HHH is not a part of those proofs.
>>>>>>>>> 
>>>>>>>>> All of the proofs work this same way.
>>>>>>>> 
>>>>>>>> No, they don't. Some proofs derive the same conclusion with an essentially
>>>>>>>> different approach.
>>>>>>>> 
>>>>>>>> However, in spite of the differences, they do share a common fieature:
>>>>>>>> your HHH is not a part of any of the proofs.
>>>>>>> 
>>>>>>> All of the conventional proofs of the HP assume that
>>>>>>> there is an *input D* that can actually do the opposite
>>>>>>> of whatever value that HHH returns.
>>>>>> 
>>>>>> Depends on what you mean by "conventional". If you merely mean proofs
>>>>>> that apply ordinary logic then there are proofs with a different
>>>>>> strategy. If you mean only proofs that use the same strategy that
>>>>>> Turing used then you are closer to the truth. But there is no assumption
>>>>>> about the exstence of such D. Its existence is proven.
>>>>> 
>>>>> In seems that way until you pay much closer attention.
>>>> 
>>>> No, it seems that way when you pay enough attention.
>>>> 
>>>>> int main()
>>>>> {
>>>>>    DDD(); // The HHH that DDD calls cannot report on the
>>>>> }        // behavior of its caller because it cannot see
>>>>>           // is caller.
>>>> 
>>>> If HHH is correctly constructed it does see DDD and everything DDD
>>>> calls. Nothing else is relevant.
>>>> 
>>> 
>>> Try to show how HHH can see anything about its own caller
>>> when HHH is not even allowed to look at its caller.
>>> 
>> 
>> It is irrelevant whether DDD is the caller of HHH or not.
>> int main()
>>  {
>>     HHH(DDD);
>>     return;
>>  }
>> 
>> Now HHH is not called from HHH, but has the same input and it should 
>> see that DDD includes the Halt7.c code, which aborts, so it should see: 
>> a halting program.
> 
> In other words you fail to understand that
> halting requires reaching a final halt state.

It is a sin to present false claims about tother peoples understanding.

-- 
Mikko