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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 13:37:11 +0300
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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
>>> 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