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From: olcott <polcott333@gmail.com>
Newsgroups: comp.theory
Subject: Re: Every D(D) simulated by H presents non-halting behavior to H ###
Date: Wed, 15 May 2024 10:24:57 -0500
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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 missing semi-colon?

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 }

The example must be simple enough so that people unfamiliar
with C will not be overwhelmed by things such as: typedef int (*ptr)();
a return value of 0 from main() also might be a little confusing.
I am trying to fit the essence of my proof on a single page.

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 past its own line 03.
This is a simple software engineering verified fact.

-- 
Copyright 2024 Olcott "Talent hits a target no one else can hit; Genius
hits a target no one else can see." Arthur Schopenhauer