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From: dbush <dbush.mobile@gmail.com>
Newsgroups: comp.theory
Subject: Re: Every sufficiently competent C programmer knows
Date: Tue, 11 Mar 2025 16:40:09 -0400
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On 3/11/2025 1:09 PM, olcott wrote:
> On 3/11/2025 11:41 AM, Fred. Zwarts wrote:
>> Op 11.mrt.2025 om 14:31 schreef olcott:
>>> On 3/11/2025 5:28 AM, Mikko wrote:
>>>> On 2025-03-10 23:41:13 +0000, olcott said:
>>>>
>>>>> 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.
>>>>
>>>> Every competent programmer knows that the information given is
>>>> insufficient to determine whether HHH emulates at all, and whether
>>>> it emulates correctly if it does.
>>>>
>>>>> Since HHH does see that same pattern that competent
>>>>> C programmers see it correctly aborts its emulation
>>>>> and rejects these inputs as non terminating.
>>>>
>>>> Whether HHH does see those patterns cannot be inferred from the 
>>>> information
>>>> given. Only about DDD one can see that it halts if HHH returns. In 
>>>> addition,
>>>> the given information does not tell whether HHH can see patterns 
>>>> that are
>>>> not there.
>>>>
>>>> How many competent programmers you have asked?
>>>>
>>>
>>> Two C programmers with masters degrees in computer science
>>> agree that DDD correctly emulated by HHH cannot possibly
>>> reach its own "return" instruction and terminate normally.
>>>
>>
>> It is clear that that HHH cannot possibly simulate itself up to the end.
> 
> I say that the cat is black and you say
> No you are wrong because the dog is white.
> 

Precisely, because we asked if the dog is white.