Path: ...!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 23:13:46 -0400 Organization: A noiseless patient Spider Lines: 170 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Thu, 13 Mar 2025 04:13:46 +0100 (CET) Injection-Info: dont-email.me; posting-host="bfda177ea2e5d824256b51a2c43e6950"; logging-data="3050027"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18BDFEt37WuiFyoI9bgC7xe" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:pKH3mEwq6uOVrlYra6fZ5Q7SIHw= Content-Language: en-US In-Reply-To: Bytes: 9031 On 3/12/2025 8:53 PM, dbush wrote: > On 3/12/2025 8:25 PM, olcott wrote: >> On 3/12/2025 6:34 PM, dbush wrote: >>> On 3/12/2025 7:28 PM, olcott wrote: >>>> On 3/12/2025 5:36 PM, dbush wrote: >>>>> 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. >>>>> >>>> >>>> >>>> Sure everyone knows that a halt decider is not kind of decider at all. >>>> >>>> >>>> >>> >>> So no answer.  Then you accept that HHH(DDD)==0 is wrong because it >>> isn't performing the above mapping required to be a solution to the >>> halting problem. >> >> A {halt decider} must be a {decider} or it is incorrect. >> > > This *is* a semantic property of the input: > > (,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 > > > And even if your claim is correct (it isn't) it doesn't matter because > we're talking about a solution to the halting problem. > > That's also what Linz is talking about.  Try to find the word "decider" > anywhere in the Linz proof. > ========== REMAINDER OF ARTICLE TRUNCATED ==========