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From: Richard Heathfield <rjh@cpax.org.uk>
Newsgroups: comp.theory
Subject: Re: How do computations actually work?
Date: Sun, 25 May 2025 10:39:24 +0100
Organization: Fix this later
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In-Reply-To: <100un10$1a22r$1@dont-email.me>

On 25/05/2025 10:14, Mikko wrote:
> On 2025-05-24 15:18:57 +0000, olcott said:

<snip>

>> All termination analyzers are required to report on the
>> behavior that their input finite string specifies.
> 
> To report correctly. Though the input string to a termination 
> analyzer usially is incomlete: the input string usually
> specifies different behavours depending on the input that is
> not shown to the termination analyzer, and the analyzer's
> report must cover all of them.


I think 'input string' is ambiguous here.

It would be clearer if people used 'program string' if they mean 
the program whose halting behaviour is being investigated and 
reserved 'input string' for when they mean the data - that is:

The analyser must determine whether the program string would 
terminate if applied to the input string.

Clearer still would be to drop 'string' and set up a couple of 
unambiguous aliases:

The analyser must determine whether program P would terminate if 
applied to input tape T.

In the above, requoted here:

 > To report correctly. Though the input string to a termination
 > analyzer usially is incomlete: the input string usually
 > specifies different behavours depending on the input that is
 > not shown to the termination analyzer, and the analyzer's
 > report must cover all of them.

I can't decide which 'input string' means P and which means T.

-- 
Richard Heathfield
Email: rjh at cpax dot org dot uk
"Usenet is a strange place" - dmr 29 July 1999
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