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From: olcott <polcott333@gmail.com>
Newsgroups: comp.theory,comp.lang.c,comp.lang.c++
Subject: Re: Every sufficiently competent C programmer knows --- Paraphrase of
 Sipser's agreement
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Date: Sat, 15 Mar 2025 16:27:00 -0500
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On 3/15/2025 5:12 AM, Mikko wrote:
> On 2025-03-14 14:39:30 +0000, olcott said:
> 
>> On 3/14/2025 4:03 AM, Mikko wrote:
>>> On 2025-03-13 20:56:22 +0000, olcott said:
>>>
>>>> On 3/13/2025 4:22 AM, Mikko wrote:
>>>>> On 2025-03-13 00:36:04 +0000, olcott said:
>>>>>
>>>>>>
>>>>>> void DDD()
>>>>>> {
>>>>>>    HHH(DDD);
>>>>>>    return;
>>>>>> }
>>>>>>
>>>>>> int DD()
>>>>>> {
>>>>>>    int Halt_Status = HHH(DD);
>>>>>>    if (Halt_Status)
>>>>>>      HERE: goto HERE;
>>>>>>    return Halt_Status;
>>>>>> }
>>>>>>
>>>>>> When HHH correctly emulates N steps of the
>>>>>> above functions none of them can possibly reach
>>>>>> their own "return" instruction and terminate normally.
>>>>>
>>>>> Nevertheless, assuming HHH is a decider, Infinite_Loop and 
>>>>> Infinite_Recursion
>>>>> specify a non-terminating behaviour, DDD specifies a terminating 
>>>>> behaviour
>>>>
>>>> _DDD()
>>>> [00002172] 55         push ebp      ; housekeeping
>>>> [00002173] 8bec       mov  ebp,esp  ; housekeeping
>>>> [00002175] 6872210000 push 00002172 ; push DDD
>>>> [0000217a] e853f4ffff call 000015d2 ; call HHH(DDD)
>>>> [0000217f] 83c404     add  esp,+04
>>>> [00002182] 5d         pop  ebp
>>>> [00002183] c3         ret
>>>> Size in bytes:(0018) [00002183]
>>>>
>>>> What is the sequence of machine language
>>>> instructions of DDD emulated by HHH such that DDD
>>>> reaches its machine address 00002183?
>>>
>>> Irrelevant off-topic distraction.
>>
>> Proving that you don't have a clue that Rice's Theorem
>> is anchored in the behavior that its finite string input
>> specifies. The depth of your knowledge is memorizing
>> quotes from textbooks.
> 
> Another irrelevant off-topic distraction, this time involving
> a false claim.
> 
> One can be a competent C programmer without knowing anyting about Rice's
> Theorem.
> 

YES.

> Rice's Theorem is about semantic properties in general, not just 
> behaviours.
> The unsolvability of the halting problem is just a special case.
> 

A property about Turing machines can be represented as the language of 
all Turing machines, encoded as strings, that satisfy that property.
http://kilby.stanford.edu/~rvg/154/handouts/Rice.html

Does THE INPUT TO simulating termination analyzer
HHH encode a C function that reaches its "return"
instruction [WHEN SIMULATED BY HHH] (The definition
of simulating termination analyzer) ???

<MIT Professor Sipser agreed to ONLY these verbatim words 10/13/2022>
     If simulating halt decider H correctly simulates its input D
     until H correctly determines that its simulated D would never
     stop running unless aborted then

     H can abort its simulation of D and correctly report that D
     specifies a non-halting sequence of configurations.
</MIT Professor Sipser agreed to ONLY these verbatim words 10/13/2022>

<Accurate Paraphrase>
     If emulating termination analyzer H emulates its input
     finite string D of x86 machine language instructions
     according to the semantics of the x86 programming language

     until H correctly determines that this emulated D cannot
     possibly reach its own "ret" instruction in any finite
     number of correctly emulated steps then

     H can abort its emulation of input D and correctly report
     that D specifies a non-halting sequence of configurations.
</Accurate Paraphrase>

> Memorizing quotes from textbooks is useful for practical purposes but
> if it is too hard for you there are other ways.
> 

The whole X represents TM X that halts on its input is inaccurate.
If you did not merely learn-by-rote you would already know this.

*Input Y to TM Z specifies a TM that halts when directly measured by Z*

-- 
Copyright 2025 Olcott "Talent hits a target no one else can hit; Genius
hits a target no one else can see." Arthur Schopenhauer