Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: olcott Newsgroups: comp.theory Subject: Re: Turing Machine computable functions apply finite string transformations to inputs VERIFIED FACT Date: Tue, 29 Apr 2025 16:38:49 -0500 Organization: A noiseless patient Spider Lines: 88 Message-ID: References: <65dddfad4c862e6593392eaf27876759b1ed0e69@i2pn2.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Tue, 29 Apr 2025 23:38:48 +0200 (CEST) Injection-Info: dont-email.me; posting-host="7c9197f4fd609c81b36b8199e294c573"; logging-data="2854053"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+deIcQJFc4KDh6sUDOBYWh" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:yAF7I3OdYcsvEJUp0yqIQdHrFvQ= Content-Language: en-US X-Antivirus-Status: Clean In-Reply-To: X-Antivirus: Norton (VPS 250429-28, 4/29/2025), Outbound message Bytes: 4863 On 4/29/2025 3:06 PM, Richard Heathfield wrote: > On 29/04/2025 20:56, olcott wrote: >> On 4/29/2025 2:39 PM, Richard Heathfield wrote: >>> On 29/04/2025 20:06, olcott wrote: >>>> On 4/29/2025 8:46 AM, Richard Heathfield wrote: >>>>> On 29/04/2025 14:11, olcott wrote: >>>>>> On 4/29/2025 2:10 AM, Richard Heathfield wrote: >>>>>>> On 29/04/2025 03:50, olcott wrote: >>>>> >>>>> >>>>> >>>>>>>> Yet it is H(P,D) and NOT P(D) that must be measured. >>>>>>> >>>>>>> Nothing /has/ to be measured. P's behaviour (halts, doesn't halt) >>>>>>> when given D as input must be /established/. >>>>>> >>>>>> No H can possibly see the behavior of P(D) >>>>> >>>>> It doesn't have to. >>>> >>>> IF IT CAN'T SEE IT THEN  IT CAN'T REPORT ON  IT. >>> >>> Yes, it can. There is no need to see the behaviour to establish >>> whether it halts. All the decider has to be able to see is the code. >>> >> >> THE CODE THAT IT CAN SEE >> unequivocally specifies that the INPUT DOES NOT HALT > > Fine. Either it's right or it's wrong. > int DD() { int Halt_Status = HHH(DD); if (Halt_Status) HERE: goto HERE; return Halt_Status; } HHH is correct DD as non-halting BECAUSE THAT IS WHAT THE INPUT TO HHH(DD) SPECIFIES. > If it's wrong, it's wrong. And if it's right we can use it to write a > program that it can't figure out. Turing proved this. > > >> >>> I, as a decider, do not need to see the following program's behaviour >>> to determine whether it halts... >>> >>> int main(void) >>> { >>>    while(1); >>>    return 0; >>> } >>> >>> ...because I can tell just by reading the code that it enters an >>> infinite loop and so will not halt. I can report on whether the >>> program halts without having to execute it. >>> >> >> IT DOES NOT WORK THAT WAY WITH PATHOLOGICAL SELF-REFERENCE. > > There's nothing in the rules to stop it. Reading the code is a perfectly > valid way of establishing whether a program halts, and Turing machines > are more than capable of reading and analysing code. Compilers do it all > the time. > Because the input to HHH(DD) specifies pathological self-reference IT CANNOT POSSIBLY HALT. > What we /can't/ do by reading the code is devise a universally accurate > termination analyser, HHH(DD) correctly rejects its input as non-halting. DD the Halting Problem counter-example input to HHH. > for the same reason we can't devise a universally > accurate termination analyser that executes the code to see what happens. > There is no evidence of that. -- Copyright 2025 Olcott "Talent hits a target no one else can hit; Genius hits a target no one else can see." Arthur Schopenhauer