Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Richard Heathfield <rjh@cpax.org.uk>
Newsgroups: comp.theory
Subject: Re: Halting Problem: What Constitutes Pathological Input
Date: Mon, 5 May 2025 22:08:51 +0100
Organization: Fix this later
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On 05/05/2025 21:10, olcott wrote:

<snip>

> That question is in many textbooks yet is still
> wrong because functions computed by models of
> computation such as Turing Machines or RASP machines
> are only allowed to use actual inputs as their basis.

Allowed by whom?

There's no law to stop people writing a TM and passing it any 
damn input they please; "only allowed" is a nonsense.

> When everyone here insists is that we simply ignore
> the above fundamental rule of how functions must be
> computed they are necessarily incorrect.

So by 'incorrect' you mean 'undecidable'. 'Incorrect' is the 
wrong word, of course.

You miss the whole point of Turing's proof, which is to show that 
some questions simply do not lend themselves to being answered by 
computers. You call such questions 'incorrect'. Everybody else 
(except for Mr Flibble) follows Turing's lead and call them 
'undecidable'. What word you use doesn't matter all that much if 
you don't need to discuss such questions with others, but the 
concept is very real and very clear. Quite why you rail against 
it is beyond me.

<snip>

-- 
Richard Heathfield
Email: rjh at cpax dot org dot uk
"Usenet is a strange place" - dmr 29 July 1999
Sig line 4 vacant - apply within