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From: Mikko <mikko.levanto@iki.fi>
Newsgroups: comp.theory
Subject: Re: Every D correctly simulated by H never reaches its final state and halts
Date: Sun, 19 May 2024 16:43:16 +0300
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On 2024-05-19 12:36:08 +0000, olcott said:

> On 5/19/2024 5:37 AM, Mikko wrote:
>> On 2024-05-18 14:38:53 +0000, olcott said:
>> 
>>> On 5/18/2024 4:45 AM, Mikko wrote:
>>>> On 2024-05-17 15:55:03 +0000, olcott said:
>>>> 
>>>>> On 5/17/2024 4:08 AM, Mikko wrote:
>>>>>> On 2024-05-17 07:25:52 +0000, Fred. Zwarts said:
>>>>>> 
>>>>>>> Op 17.mei.2024 om 03:15 schreef olcott:
>>>>>>>> The following is self-evidently true on the basis of the
>>>>>>>> semantics of the C programming language.
>>>>>>>> 
>>>>>>>> typedef int (*ptr)();  // ptr is pointer to int function
>>>>>>>> 00 int H(ptr x, ptr x);
>>>>>>>> 01 int D(ptr x)
>>>>>>>> 02 {
>>>>>>>> 03   int Halt_Status = H(x, x);
>>>>>>>> 04   if (Halt_Status)
>>>>>>>> 05     HERE: goto HERE;
>>>>>>>> 06   return Halt_Status;
>>>>>>>> 07 }
>>>>>>>> 08
>>>>>>>> 09 int main()
>>>>>>>> 10 {
>>>>>>>> 11   H(D,D);
>>>>>>>> 12   return 0;
>>>>>>>> 13 }
>>>>>>>> 
>>>>>>>> In the above case a simulator is an x86 emulator that correctly
>>>>>>>> emulates at least one of the x86 instructions of D in the order
>>>>>>>> specified by the x86 instructions of D.
>>>>>>>> 
>>>>>>>> This may include correctly emulating the x86 instructions of H
>>>>>>>> in the order specified by the x86 instructions of H thus calling
>>>>>>>> H(D,D) in recursive simulation.
>>>>>>>> 
>>>>>>>> Any H/D pair matching the above template where
>>>>>>>> D(D) is simulated by the same H(D,D) that it calls
>>>>>>>> cannot possibly reach its own line 06 and halt.
>>>>>>>> 
>>>>>>>> *This is a simple software engineering verified fact*
>>>>>>>> 
>>>>>>> 
>>>>>>> Note that olcott defines 'verified fact' as 'proven fact', but he is 
>>>>>>> unable to show the proof. So, it must be read as 'my belief'.
>>>>>> 
>>>>>> A "proven fact" without a proof is not worse than a "verified fact"
>>>>>> without a verification.
>>>>>> 
>>>>> 
>>>>> *I updated my wording*
>>>>> It is self-evidently true to anyone having sufficient knowledge
>>>>> of the semantics of the C programming language.
>>>> 
>>>> No, it is not. I would know if it were.
>>>> 
>>> 
>>> If you do not understand that a single valid counter-example
>>> would refute my claim then you don't know enough about proofs.
>> 
>> Your claim
>> 
> 
> Most people to not know the difference between deductive proof
> ]and inductive evidence.

Most people don't read comp.theory so here we needn't care.

>>>>> It is self-evidently true to anyone having sufficient knowledge
>>>>> of the semantics of the C programming language.
>> 
>> is a little unclear about the meaning of "It" but I think it
>> is false for any reasonable interpretation. Can I call myself
>> a counter-example?


-- 
Mikko