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: Turing Machine computable functions apply finite string transformations to inputs +++ Date: Mon, 28 Apr 2025 18:11:52 -0400 Organization: A noiseless patient Spider Lines: 58 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 00:11:53 +0200 (CEST) Injection-Info: dont-email.me; posting-host="ffd05fb72978086508f1b479be465222"; logging-data="3585230"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+D+B3X3Ten9A0w/DAr+wWH" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:Qy7UB+/4SKdelyK1wV2xUeR/Qio= In-Reply-To: Content-Language: en-US Bytes: 3694 On 4/28/2025 5:47 PM, olcott wrote: > On 4/28/2025 3:21 PM, Richard Heathfield wrote: >> On 28/04/2025 21:03, olcott wrote: >>> On 4/28/2025 2:58 PM, dbush wrote: >> >> >> >>>> Category error.  The halting function below is fully defined, and >>>> this mapping is not computable *as you have explicitly admitted*. >>>> >>> >>> Neither is the square root of an actual onion computable. >>> >>> Turing Computable Functions are required to apply finite >>> string transformations to their inputs. The function defined >>> below ignores that requirement PROVING THAT IT IS INCORRECT. >> >> No, it proves that you agree that it's not a computable function. QED. >> > > Computing the actual behavior the direct execution > of any input is ALWAYS IMPOSSIBLE. So you again agree that Linz is correct. > > No halt decider So you assume that an algorithm exists that can perform the following mapping: Given any algorithm (i.e. a fixed immutable sequence of instructions) X described as with input Y: (,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 > can ever directly see the actual > behavior of any directly executed input. > And you reach a contradiction, proving the assumption false, as Linz proved and you *explicitly* agreed is correct. >>>> Given any algorithm (i.e. a fixed immutable sequence of >>>> instructions) X described as with input Y: >>>> >>>> (,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 >> >> > >