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From: Richard Heathfield <rjh@cpax.org.uk>
Newsgroups: comp.theory
Subject: Re: Functions computed by Turing Machines MUST apply finite string
transformations to inputs
Date: Sun, 4 May 2025 07:25:42 +0100
Organization: Fix this later
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On 04/05/2025 01:20, Mike Terry wrote:
> On 03/05/2025 20:45, Richard Heathfield wrote:
<snip>
>>
>> I am conscious that you have already explained to me (twice!)
>> that Mr O's approach is aimed not at overturning the
>> overarching indecidability proof but a mere detail of Linz's
>> proof. Unfortunately, your explanations have not managed to
>> establish a firm root in what passes for my brain.
Third time's a charm, I think, or at least I'm further forward.
(See question about a mile VVVVVsouthVVVVV of here.)
In case I ever bail again, you have my full permission to remind
me of <~/alldata/usenet/M_Terry_explains_olcott_reasoning.eml>
where I have saved your reply for future re-enlightenment.
>> This may be
>> because I'm too dense to grok them, or possibly it's because
>> your explanations are TOAST (see above).
Turned out to be 50/50.
> I generally think I post way too much,
I think Usenauts are best measured by their S/N ratio. That is,
it's what you post rather than how much there is of it.
> and tend to wander off
> topic with unnecessary background and so on,
Isaac Asimov was always at his happiest when starting an essay
with the magic words "The Ancient Greeks..." In 1965 he wrote a
book to be called "The Neutrino". He spent the first three
quarters or so of the book on what he considered to be
/necessary/ background, and Chapter 500-or-so is called "Enter
The Neutrino". When he got the proofs back for checking, he saw
that his copy editor had pencilled into the margin "AT LAST!"
> and probably I write
> too much from a "maths" perspective, because that's my
> background. Not sure if I can change any of that! :) Just ask
> if I use obscure notation or let me know if I'm going too
> fast/slow. Part of the problem is I don't know your background
> and what things you're super familiar with.
ISTR that I have recently gone on record as claiming (when asked
if I have ever done any programming) to be a professional potato
painter. The claim is rather less accurate than I generally try
to be, and whilst it is true that I am super familiar (and
perhaps too familiar) with potatoes, I haven't actually painted
one since infants' school.
My background? Unfortunately my potato-painting career never
really took off, so I decided instead to earn my corn writing
computer programs for a living.
Any good?
Well, maybe, maybe not. But I'll let my peers answer that one, if
I can find some for you.
They say you should never Google yourself because you might not
like what you read. But what the hell, yeah? My seventh hit was
for an ancient Usenet thread entitled "Richard HeathField. Bad
ideas!" in which I am severely taken to task by a chap called
"paulcr". It makes an entertaining read. His beef is with my
claim that there's no /one/ way to do non-blocking input that can
be guaranteed to work.
https://groups.google.com/g/comp.lang.c.moderated/c/W9ViD37NpzE
I would draw your attention not so much to my accuser as to the
counsel for the defence. Doug Gwyn's name, for example, can be
found in the acknowledgements section of K&R, and Francis
Glassborow was for many years the chairman of the Association of
C and C++ Users.
Or if you prefer pictures, here's one I prepared earlier.
Figuring out what it does is easy - suck it and see the Olcott
way. Figuring out how it works, though, is a touch more
challenging, and I leave it as an exercise with which to while
away a Sunday morning:
#include <stdlib.h>
#include <stdio.h>
#define O int
#define B main
#define F char
#define U if
#define S atoi
#define C for
#define A putchar
#define T '*'
#define E ' '
#define D '\n'
#define c ==
#define o =
#define d ++
#define e return
#define r ||
O
B (
O k
, F
* v
[ ]
) {
O i
, j = 9
; U ( k > 1
) { j = S
( v [ 1
] ) ; }
U ( ! (
j > 0 )
) { j =
5 ; } U ( (
j & 1 ) c 0 ) {
d j ; } C (
i = 0 ;
i < j * j
; A ( i / j
c ( 3 * j
) / 2 -
( i % j + 1
) r i / j c j /
2 - i % j r
i / j c
j / 2 +
i % j r
i / j c
i % j -
j / 2 ? T
: E ) , i d
, i % j
c 0
? A
( D
) :
0 )
; e
0 ;
}
>> You have said, I think, that Olcott doesn't need a universal
>> decider in order to prove his point. But a less ambitious
>> decider doesn't contradict Linz's proof, surely? So once more
>> for luck, what exactly would PO be establishing with his
>> non-universal and impatient simulator if he could only get it
>> to work?
>
> Yes. PO is aiming to refute the /proof method/ that Linz (and
> similar) proofs use, i.e. to attack the /reasoning/ behind the
> proof. In effect, he is saying that his HHH/DD provide a
> counter-example to that reasoning. His HHH/DD are not full halt
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