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From: Mikko <mikko.levanto@iki.fi>
Newsgroups: comp.theory
Subject: Re: Simulating termination analyzers by dummies --- What does halting mean?
Date: Thu, 20 Jun 2024 18:08:34 +0300
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On 2024-06-20 05:40:28 +0000, olcott said:

> On 6/20/2024 12:29 AM, Mikko wrote:
>> On 2024-06-19 14:05:29 +0000, olcott said:
>> 
>>> On 6/19/2024 4:29 AM, Alan Mackenzie wrote:
>>>> olcott <polcott333@gmail.com> wrote:
>>>>> On 6/18/2024 4:36 PM, Alan Mackenzie wrote:
>>>>>> [ Followup-To: set ]
>>>> 
>>>>>> In comp.theory olcott <polcott333@gmail.com> wrote:
>>>>>>> On 6/18/2024 12:57 PM, joes wrote:
>>>>>>>> Am Tue, 18 Jun 2024 12:25:44 -0500 schrieb olcott:
>>>>>>>>> On 6/18/2024 12:06 PM, joes wrote:
>>>>>>>>> void DDD()
>>>>>>>>> {
>>>>>>>>> H0(DDD);
>>>>>>>>> }
>>>>>>>>> DDD correctly simulated by any H0 cannot possibly halt.
>>>>>>>>>> DDD halts iff H0 halts.
>>>> 
>>>>>>>> So H0 returns "doesn't halt" to DDD, which then stops running,
>>>>>>>> so H0 should have returned "halts".
>>>> 
>>>>>>> This was three messages ago.
>>>>>>> I had to make sure that you understood that halting
>>>>>>> does not mean stopping for any reason and only includes
>>>>>>> the equivalent of terminating normally.
>>>> 
>>>>>> No.  You're wrong, here.  A turing machine is either running or it's
>>>>>> halted.  There's no third alternative.  If your C programs are not in one
>>>>>> of these two states, they're not equivalent to turing machines.
>>>> 
>>>>> Although I agree with this there seems to be nuances of
>>>>> disagreement across the experts.
>>>> 
>>>> I doubt that very much.  The whole point of turing machines is to remove
>>>> ambiguity and unneeded features from the theory of computation.  A third
>>>> alternative state is unneeded.
>>>> 
>>> 
>>> Some people say that a TM can halt in a non-final state.
>> 
>> People may use different words to express the same facts. What some
>> people call "halting in a non-final state" is called "rejecting" by
>> some other people. But the facts are what they are independently of
>> the words used to express them.
> 
> Ambiguity and vagueness make communication less effective.

As does use of common words and expressions for uncommon meanings.

> I use C because there are zero gaps in exactly what it means.

THere are lont of gaps in C. Some are mistakes that are corrected in
technical corrigenda. Others are undefined and implementation defined
behaviour. Your program uses non-standard extensions to C so it does
not communicate well. If also is too big to be a part of a publishable
article.

-- 
Mikko