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From: "Fred. Zwarts" <F.Zwarts@HetNet.nl>
Newsgroups: comp.theory
Subject: Re: DDD simulated by HHH cannot possibly halt (Halting Problem)
Date: Fri, 11 Apr 2025 10:21:28 +0200
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Op 11.apr.2025 om 01:20 schreef olcott:
> On 4/10/2025 3:49 AM, Fred. Zwarts wrote:
>> Op 09.apr.2025 om 21:20 schreef olcott:
>>> On 4/9/2025 1:58 PM, Fred. Zwarts wrote:
>>>> Op 09.apr.2025 om 19:29 schreef olcott:
>>>>>
>>>>> On 4/8/2025 10:31 AM, Fred. Zwarts wrote:
>>>>>> Op 08.apr.2025 om 17:13 schreef olcott:
>>>>>>> On 4/8/2025 2:45 AM, Fred. Zwarts wrote:
>>>>>>>> Op 08.apr.2025 om 06:33 schreef olcott:
>>>>>>>>>
>>>>>>>>> typedef void (*ptr)();
>>>>>>>>> int HHH(ptr P);
>>>>>>>>>
>>>>>>>>> int DD()
>>>>>>>>> {
>>>>>>>>>    int Halt_Status = HHH(DD);
>>>>>>>>>    if (Halt_Status)
>>>>>>>>>      HERE: goto HERE;
>>>>>>>>>    return Halt_Status;
>>>>>>>>> }
>>>>>>>>>
>>>>>>>>> int main()
>>>>>>>>> {
>>>>>>>>>    HHH(DD);
>>>>>>>>> }
>>>>>>>>>
>>>>>>>>> *Simulating termination analyzer Principle*
>>>>>>>>> It is always correct for any simulating termination
>>>>>>>>> analyzer to stop simulating and reject any input that
>>>>>>>>> would otherwise prevent its own termination.
>>>>>>>>
>>>>>>>>
>>>>>>>> In this case there is nothing to prevent, because the finite 
>>>>>>>> string specifies a program that halts. 
>>>>>>>
>>>>>>> int DD()
>>>>>>> {
>>>>>>>    int Halt_Status = HHH(DD);
>>>>>>>    if (Halt_Status)
>>>>>>>      HERE: goto HERE;
>>>>>>>    return Halt_Status;
>>>>>>> }
>>>>>>>
>>>>>>> This stuff is simply over-your-head.
>>>>>>> HHH(DD) meets the above: *Simulating termination analyzer Principle*
>>>>>>> Anyone with sufficient competence with the C programming language
>>>>>>> will understand this.
>>>>>>>
>>>>>> Everyone with a little bit of C knowledge understands that if HHH 
>>>>>> returns with a value 0, then DDD halts. 
>>>>>
>>>>> DDD CORRECTLY SIMULATED BY HHH
>>>>> NOT ANY OTHER DAMN DDD IN THE UNIVERSE NITWIT.
>>>>>
>>>> If HHH would correctly simulate DD (and the functions called by DD) 
>>>> then the simulated HHH would return to DD and DD would halt.
>>>
>>> No way, José:
>>> By "correctly simulate" I mean a simulation or an emulation
>>> of DD by HHH that obeys the semantics of the C or the x86utm
>>> programming languages respectfully. This expressly includes
>>> that HHH simulates/emulates itself simulating/emulating DD.
> 
>> That would make HHH to never halt.
> 
> *Simulating termination analyzer Principle*
> It is always correct for any simulating termination
> analyzer to stop simulating and reject any input that
> would otherwise prevent its own termination.
> 
Once you change the input to a DD using a HHH that aborts, there is 
nothing to prevent. It is only your dream of na infinite recursion that 
makes HHH abort, although the input has a behaviour with only finite 
recursions.