Path: ...!weretis.net!feeder9.news.weretis.net!news.quux.org!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: dbush Newsgroups: comp.theory Subject: Re: Every sufficiently competent C programmer knows --- Semantic Property of Finite String Date: Wed, 12 Mar 2025 18:36:19 -0400 Organization: A noiseless patient Spider Lines: 129 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Wed, 12 Mar 2025 23:36:20 +0100 (CET) Injection-Info: dont-email.me; posting-host="8716d0356783f046d50792ab42ba1cd2"; logging-data="2957945"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+oluRZnyYWUgjpVZ+FOOvX" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:Tpi2ab4mP4Wrwwv5ppAfLUrzrew= In-Reply-To: Content-Language: en-US Bytes: 6976 On 3/12/2025 6:31 PM, olcott wrote: > On 3/12/2025 5:03 PM, dbush wrote: >> On 3/12/2025 5:38 PM, olcott wrote: >>> On 3/12/2025 3:53 PM, dbush wrote: >>>> On 3/12/2025 4:29 PM, olcott wrote: >>>>> On 3/12/2025 2:16 PM, dbush wrote: >>>>>> On 3/11/2025 10:46 PM, olcott wrote: >>>>>>> On 3/11/2025 9:41 PM, dbush wrote: >>>>>>>> On 3/11/2025 10:39 PM, olcott wrote: >>>>>>>>> On 3/11/2025 9:37 PM, dbush wrote: >>>>>>>>>> On 3/11/2025 10:36 PM, olcott wrote: >>>>>>>>>>> On 3/11/2025 9:32 PM, dbush wrote: >>>>>>>>>>>> On 3/11/2025 10:31 PM, olcott wrote: >>>>>>>>>>>>> On 3/11/2025 9:18 PM, dbush wrote: >>>>>>>>>>>>>> On 3/11/2025 10:06 PM, olcott wrote: >>>>>>>>>>>>>>> On 3/11/2025 9:02 PM, dbush wrote: >>>>>>>>>>>>>>>> On 3/11/2025 9:41 PM, Richard Heathfield wrote: >>>>>>>>>>>>>>>>> On 12/03/2025 01:22, olcott wrote: >>>>>>>>>>>>>>>>>> DDD correctly simulated by HHH never reaches its >>>>>>>>>>>>>>>>>> own "return" instruction and terminates normally >>>>>>>>>>>>>>>>>> in any finite or infinite number of correctly >>>>>>>>>>>>>>>>>> simulated steps. >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> If it correctly simulates infinitely many steps, it >>>>>>>>>>>>>>>>> doesn't terminate. Look up "infinite". >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> But your task is to decide for /any/ program, not just >>>>>>>>>>>>>>>>> DDD. That, as you are so fond of saying, is >>>>>>>>>>>>>>>>> 'stipulated', and you can't get out of it. The whole >>>>>>>>>>>>>>>>> point of the Entscheidungsproblem is its universality. >>>>>>>>>>>>>>>>> Ignore that, and you have nothing. >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> Given that his code has HHH(DD) returning 0, >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> THESE ARE THE WORDS ANYONE THAT DODGES THESE >>>>>>>>>>>>>>> WORDS WILL BE TAKEN FOR A LIAR >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> void DDD() >>>>>>>>>>>>>>> { >>>>>>>>>>>>>>>    HHH(DDD); >>>>>>>>>>>>>>>    return; >>>>>>>>>>>>>>> } >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> DDD correctly simulated by HHH never reaches its >>>>>>>>>>>>>>> own "return" instruction and terminates normally >>>>>>>>>>>>>>> in any finite or infinite number of correctly >>>>>>>>>>>>>>> simulated steps. >>>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> Changing the input is not allowed. >>>>>>>>>>>>> >>>>>>>>>>>>> *You are simply lying that any input was ever changed* >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> You did precisely that when you hypothesize different code >>>>>>>>>>>> for HHH. >>>>>>>>>>>> >>>>>>>>>>>> Changing the input is not allowed. >>>>>>>>>>> >>>>>>>>>>> *THIS IS WHAT MY ORIGINAL WORDS MEANT* >>>>>>>>>>> HHH is the infinite set of every possible C function >>>>>>>>>>> that correctly emulates N steps of its input where >>>>>>>>>>> N any finite positive integer. >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> In other words, you're changing the input. >>>>>>>>>> >>>>>>>>>> Changing the input is not allowed. >>>>>>>>> >>>>>>>>> It is an infinite set of HHH/DDD pairs having the >>>>>>>>> property that DDD[0] ... DDD[N] never halts. >>>>>>>>> >>>>>>>> >>>>>>>> In other words, you're not answering the question that a >>>>>>>> solution to the halting problem is required to answer: >>>>>>>> >>>>>>>> (,Y) maps to 1 if and only if X(Y) halts when executed directly >>>>>>>> (,Y) maps to 0 if and only if X(Y) does not halt when >>>>>>>> executed directly >>>>>>>> >>>>>>> >>>>>>> Yes I am yet you refuse to pay anywhere near close >>>>>>> enough attention to see how I already fully addressed this. >>>>>>> If you pay 100% perfect attention you might get it. >>>>>>> >>>>>> >>>>>> False.  (,null) maps to 1 as per the above requirements, but >>>>>> your HHH maps (,null) to 0, therefore it fails to meet the >>>>>> requirements. >>>>> >>>>> >>>>> >>>> >>>> >>>> So no response?  I'll take it that you agree with the above. >>> >>> Making sure to always give credit where credit is due this >>> point in our conversation is the point where I first translated >>> my perspective into the semantic property of a finite string. >>> >>> A decider is required to report on a semantic (or syntactic) >>> property of its input finite string (even if Rice incorrectly >>> says this is impossible in this case) and not allowed to report >>> on any damn thing else. >>> >>> The fact that DDD calls HHH(DDD) in recursive emulation >>> an aspect of the semantics of the input finite string >>> that cannot be correctly ignored. >>> >>> >> >> Remember the stipulative definition of a solution to the halting problem: >> >> > > Is to map the input finite string to the semantic property > of this finite string. Any other mapping contradicts the > definition of a decider. And that property is as follows: (,Y) maps to 1 if and only if X(Y) halts when executed directly (,Y) maps to 0 if and only if X(Y) does not halt when executed directly I should also point out that I never mentioned anything about a "decider", simply "a solution to the halting problem". Neither did Linz.