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: Mikko Newsgroups: comp.theory Subject: Re: How do computations actually work? Date: Mon, 26 May 2025 11:38:33 +0300 Organization: - Lines: 108 Message-ID: <10119a9$1tver$1@dont-email.me> References: <100jo18$2mhfd$1@dont-email.me> <100jpv9$2m0ln$4@dont-email.me> <100kt0c$2tae8$3@dont-email.me> <100ktr7$2reaa$1@dont-email.me> <100l09v$2tae8$5@dont-email.me> <100l1ov$2ul3j$1@dont-email.me> <100l3jh$2v0e9$1@dont-email.me> <100l5c8$2ul3j$2@dont-email.me> <100l75g$2vpq3$1@dont-email.me> <100l887$2ul3i$2@dont-email.me> <100l9gh$30aak$1@dont-email.me> <100lc4o$30pgm$1@dont-email.me> <100ld1u$312c9$1@dont-email.me> <100lg4g$31jt3$1@dont-email.me> <100lkdv$32ib3$1@dont-email.me> <100lmif$32v06$1@dont-email.me> <100lmp3$32ven$1@dont-email.me> <100m319$38k55$2@dont-email.me> <87jz69xlpx.fsf@nosuchdomain.example.com> <100mder$39slu$2@dont-email.me> <100oipb$3oge1$1@dont-email.me> <100onkd$3t5cb$1@dont-email.me> <100p6vj$3vlgq$1@dont-email.me> <100q6b1$5buc$2@dont-email.me> <100rtvq$ji9l$1@dont-email.me> <100sod2$p071$6@dont-email.me> <100umo8$1a058$1@dont-email.me> <100vaoj$1d5lg$9@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Mon, 26 May 2025 10:38:34 +0200 (CEST) Injection-Info: dont-email.me; posting-host="481644667b235b9569d59ad7c3136bac"; logging-data="2031067"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18rIZcOiNdnen/5Xt/KgjRS" User-Agent: Unison/2.2 Cancel-Lock: sha1:fSf5BCs4blfOEuQ0IQXAFP/TQYw= Bytes: 6084 On 2025-05-25 14:50:58 +0000, olcott said: > On 5/25/2025 4:09 AM, Mikko wrote: >> On 2025-05-24 15:25:21 +0000, olcott said: >> >>> On 5/24/2025 2:54 AM, Mikko wrote: >>>> On 2025-05-23 16:04:49 +0000, olcott said: >>>> >>>>> On 5/23/2025 2:09 AM, Mikko wrote: >>>>>> On 2025-05-23 02:47:40 +0000, olcott said: >>>>>> >>>>>>> On 5/22/2025 8:24 PM, Mike Terry wrote: >>>>>>>> On 22/05/2025 06:41, Richard Heathfield wrote: >>>>>>>>> On 22/05/2025 06:23, Keith Thompson wrote: >>>>>>>>>> Richard Heathfield writes: >>>>>>>>>>> On 22/05/2025 00:14, olcott wrote: >>>>>>>>>>>> On 5/21/2025 6:11 PM, Richard Heathfield wrote: >>>>>>>>>> [...] >>>>>>>>>>>>> Turing proved that what you're asking is impossible. >>>>>>>>>>>>> >>>>>>>>>>>> That is not what he proved. >>>>>>>>>>> >>>>>>>>>>> Then you'll be able to write a universal termination analyser that can >>>>>>>>>>> correctly report for any program and any input whether it halts. Good >>>>>>>>>>> luck with that. >>>>>>>>>> >>>>>>>>>> Not necessarily. >>>>>>>>> >>>>>>>>> Of course not. But I'm just reflecting. He seemed to think that my >>>>>>>>> inability to write the kind of program Turing envisaged (an inability >>>>>>>>> that I readily concede) is evidence for his argument. Well, what's >>>>>>>>> sauce for the goose is sauce for the gander. >>>>>>>>> >>>>>>>>>> Even if olcott had refuted the proofs of the >>>>>>>>>> insolvability of the Halting Problem -- or even if he had proved >>>>>>>>>> that a universal halt decider is possible >>>>>>>>> >>>>>>>>> And we both know what we both think of that idea. >>>>>>>>> >>>>>>>>>> -- that doesn't imply >>>>>>>>>> that he or anyone else would be able to write one. >>>>>>>>> >>>>>>>>> Indeed. >>>>>>>>> >>>>>>>>>> I've never been entirely clear on what olcott is claiming. >>>>>>>>> >>>>>>>>> Nor I. Mike Terry seems to have a pretty good handle on it, but no >>>>>>>>> matter how clearly he explains it to me my eyes glaze over and I start >>>>>>>>> to snore. >>>>>>>> >>>>>>>> Hey, it's the way I tell 'em! >>>>>>>> >>>>>>>> Here's what the tabloids might have said about it, if it had made the >>>>>>>> front pages when the story broke: >>>>>>>> >>>>>>>>   COMPUTER BOFFIN IS TURING IN HIS GRAVE! >>>>>>>> >>>>>>>>   An Internet crank claims to have refuted Linz HP proof by creating a >>>>>>>>   Halt Decider that CORRECTLY decides its own "impossible input"! >>>>>>>>   The computing world is underwhelmed. >>>>>>>> >>>>>>>> Better?  (Appologies for the headline, it's the best I could come up with.) >>>>>>>> >>>>>>>> Mike. >>>>>>>> >>>>>>> >>>>>>> There is a key detail about ALL of these proofs >>>>>>> that no one has paid attention to for 90 years. >>>>>>> >>>>>>> It is impossible to define *AN INPUT* to HHH that >>>>>>> does the opposite of whatever value that HHH returns. >>>>>> >>>>>> That is a key detail about HHH. Your HHH is not a part of those proofs. >>>>> >>>>> All of the proofs work this same way. >>>> >>>> No, they don't. Some proofs derive the same conclusion with an essentially >>>> different approach. >>>> >>>> However, in spite of the differences, they do share a common fieature: >>>> your HHH is not a part of any of the proofs. >>> >>> All of the conventional proofs of the HP assume that >>> there is an *input D* that can actually do the opposite >>> of whatever value that HHH returns. >> >> Depends on what you mean by "conventional". If you merely mean proofs >> that apply ordinary logic then there are proofs with a different >> strategy. If you mean only proofs that use the same strategy that >> Turing used then you are closer to the truth. But there is no assumption >> about the exstence of such D. Its existence is proven. > > In seems that way until you pay much closer attention. No, it seems that way when you pay enough attention. > int main() > { > DDD(); // The HHH that DDD calls cannot report on the > } // behavior of its caller because it cannot see > // is caller. If HHH is correctly constructed it does see DDD and everything DDD calls. Nothing else is relevant. -- Mikko