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From: immibis <news@immibis.com>
Newsgroups: comp.theory
Subject: Re: Every D(D) simulated by H presents non-halting behavior to H ###
Date: Sat, 18 May 2024 10:54:05 +0200
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On 16/05/24 16:50, olcott wrote:
> On 5/16/2024 5:48 AM, Mikko wrote:
>> On 2024-05-15 15:24:57 +0000, olcott said:
>>
>>> On 5/15/2024 3:18 AM, Mikko wrote:
>>>> On 2024-05-14 14:35:42 +0000, olcott said:
>>>>
>>>>> On 5/14/2024 4:52 AM, Mikko wrote:
>>>>>> On 2024-05-13 14:43:09 +0000, olcott said:
>>>>>>
>>>>>>> On 5/13/2024 4:14 AM, Mikko wrote:
>>>>>>>> On 2024-05-13 04:54:30 +0000, immibis said:
>>>>>>>>
>>>>>>>>> On 10/05/24 19:55, Alan Mackenzie wrote:
>>>>>>>>>> [ Followup-To: set ]
>>>>>>>>>>
>>>>>>>>>> In comp.theory olcott <polcott333@gmail.com> wrote:
>>>>>>>>>>
>>>>>>>>>> [ .... ]
>>>>>>>>>>
>>>>>>>>>> I've tried out your much spammed code on GCC (see below).  It 
>>>>>>>>>> is clear
>>>>>>>>>> you have never built or run this code, which ironically can't 
>>>>>>>>>> reach Line
>>>>>>>>>> 06.  It can't even reach line 00.
>>>>>>>>>>
>>>>>>>>>>> Richard tried to get away with D never simulated by H as an 
>>>>>>>>>>> example
>>>>>>>>>>> of D simulated by H:
>>>>>>>>>>
>>>>>>>>>>> Message-ID: <v0ummt$2qov3$2@i2pn2.org>
>>>>>>>>>>> On 5/1/2024 7:28 PM, Richard Damon wrote:
>>>>>>>>>>
>>>>>>>>>>> *That people say they know I am wrong yet will not show the 
>>>>>>>>>>> detailed*
>>>>>>>>>>> *steps of how I am wrong indicates that they are probably liars*
>>>>>>>>>>
>>>>>>>>>> You have said, or at least implied that your code fragment is 
>>>>>>>>>> runnable.
>>>>>>>>>> I think you are the liar, here.
>>>>>>>>>>
>>>>>>>>>>> 00 int H(ptr x, ptr x)  // ptr is pointer to int function
>>>>>>>>>>> 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 }
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> .  These are the diagnostics generated by GCC:
>>>>>>>>>>
>>>>>>>>> And the halting problem is about Turing machines, anyway.
>>>>>>>>
>>>>>>>> Not necessarily. The same question can be asked about different 
>>>>>>>> machines.
>>>>>>>> The restriction to Turing machines is just one way to ensure 
>>>>>>>> that the
>>>>>>>> problem is well defined.
>>>>>>>>
>>>>>>>
>>>>>>> Well put. All computable functions even if written in C.
>>>>>>
>>>>>> You still must ensure that the problem is well defined. With C 
>>>>>> there is
>>>>>> the problem that conforming C programs often fail to be strictly 
>>>>>> conforming.
>>>>>> If a program is not strictly conforming it may be interpreted as 
>>>>>> halting
>>>>>> by some implementation and non-halting or incorrect by another.
>>>>>>
>>>>>
>>>>> 00 int H(ptr x, ptr x)  // ptr is pointer to int function
>>>>> 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 }
>>>>>
>>>>> One can correctly determine that every D simulated by H
>>>>> never reaches past its own line 03.
>>>>
>>>> That is not strictly conforming and hardly conforming at all.
>>>>
>>>
>>> What trivial syntactic error that has no effect
>>> what-so-ever on the semantics do you believe remains?
>>
>> A trivial sysntactic error means that the program is not strictly
>> conforming. It may be conforming if some liberal compiler accepts
>> it.
>>
>>> A missing semi-colon?
>>
>> Normal semantics is that the program is not executed.
>>
>>> 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 }
>>
>> Can you find any compiler that is liberal enough to accept that?
>>
> 
> It has been fully operational code under Windows and
> Linux for two years.
> 

and it halts and it thinks it does not halt