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Re: How to write a self-referencial TM?

From Mikko <mikko.levanto@iki.fi>
Newsgroups comp.theory
Subject Re: How to write a self-referencial TM?
Date 2025-05-15 10:24 +0300
Organization -
Message-ID <10044ri$3108g$1@dont-email.me> (permalink)
References (7 earlier) <1002nvo$2k04b$5@dont-email.me> <87plgb9d4i.fsf@nosuchdomain.example.com> <1002tma$2k04c$5@dont-email.me> <87ldqyapfk.fsf@nosuchdomain.example.com> <PH7VP.224787$JJT6.10824@fx16.ams4>

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On 2025-05-14 21:13:19 +0000, Mr Flibble said:

> On Wed, 14 May 2025 13:49:03 -0700, Keith Thompson wrote:
> 
>> Richard Heathfield <rjh@cpax.org.uk> writes:
>>> On 14/05/2025 21:00, Keith Thompson wrote:
>>> <snip>
>>> 
>>>> I presume that one-way and two-way infinite tapes are computationally
>>>> equivalent, so the distinction doesn't matter all that much.
>>>> (Though with a one-way tape, I'm not sure what happens if the TM runs
>>>> off the end of the tape.)
>>> 
>>> I should imagine that you could build one hell of a stack on one-way
>>> tape.
>>> 
>>> Of course, the tape doesn't /have/ to be infinite. It only has to be
>>> long enough so that you /don't/ run off the end. Just how long that is
>>> depends on what problem you're addressing.
>>> 
>>> In the Real World, tapes can't be infinite, so an implementor has to
>>> decide how long 'long enough' is.
>> 
>> TM's don't necessarily operate in the Real World.
>> 
>>> If the TM's alphabet consisted of 256 discrete symbols (no reason why
>>> not) a megabyte would give you a disk-based 'tape' a million cells
>>> long.
>>> 
>>> Ought to be enough for `take one down and pass it around'.
>> 
>> Sure.  "Infinite tape" might be more precisely expressed as "sufficient
>> tape".  But a TM that advances in one direction along the tape in a loop
>> will require more than any finite length of tape if you leave it running
>> long enough, though the amount of tape it consumes in any finite number
>> of steps is still finite.  For that kind of TM in particular, "infinite
>> tape" is a convenient shorthand.
> 
> Flibble's Law still applies:
> 
> If a problem permits infinite behavior in its formulation, it permits
> infinite analysis of that behavior in its decidability scope.

You cannot pose in finite time a problem that has an infinite behaviour
in its formulation. If the problem will not be posed in a finite time
it will never be solved.

-- 
Mikko

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Thread

How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-14 13:13 +0800
  Re: How to write a self-referencial TM? Richard Heathfield <rjh@cpax.org.uk> - 2025-05-14 07:02 +0100
  Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-14 09:51 -0500
    Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-15 00:43 +0800
      Re: How to write a self-referencial TM? Richard Heathfield <rjh@cpax.org.uk> - 2025-05-14 18:14 +0100
        Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-15 01:33 +0800
          Re: How to write a self-referencial TM? Richard Heathfield <rjh@cpax.org.uk> - 2025-05-14 18:49 +0100
            Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-15 02:01 +0800
              Re: How to write a self-referencial TM? Richard Heathfield <rjh@cpax.org.uk> - 2025-05-14 19:38 +0100
                Re: How to write a self-referencial TM? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-14 13:00 -0700
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-14 15:02 -0500
                Re: How to write a self-referencial TM? Richard Heathfield <rjh@cpax.org.uk> - 2025-05-14 21:19 +0100
                Re: How to write a self-referencial TM? Richard Heathfield <rjh@cpax.org.uk> - 2025-05-14 21:16 +0100
                Re: How to write a self-referencial TM? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-14 13:49 -0700
                Re: How to write a self-referencial TM? Mr Flibble <flibble@red-dwarf.jmc.corp> - 2025-05-14 21:13 +0000
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-15 10:24 +0300
                Re: How to write a self-referencial TM? Richard Heathfield <rjh@cpax.org.uk> - 2025-05-14 22:28 +0100
                Re: How to write a self-referencial TM? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-14 14:40 -0700
                Re: How to write a self-referencial TM? Richard Heathfield <rjh@cpax.org.uk> - 2025-05-14 23:02 +0100
                Re: How to write a self-referencial TM? Andy Walker <anw@cuboid.co.uk> - 2025-05-15 01:09 +0100
                Re: How to write a self-referencial TM? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-05-14 17:19 -0700
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-15 09:38 +0800
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-15 09:58 +0800
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-15 10:11 +0800
                Re: How to write a self-referencial TM? Ben Bacarisse <ben@bsb.me.uk> - 2025-05-15 00:55 +0100
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-15 10:17 +0300
      Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-14 12:24 -0500
        Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-15 01:39 +0800
          Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-14 12:45 -0500
            Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-15 02:13 +0800
        Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-15 01:53 +0800
          Re: How to write a self-referencial TM? Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2025-05-15 17:08 +0100
            Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-15 11:47 -0500
              Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-16 03:57 +0800
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-15 15:50 -0500
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-16 10:33 +0300
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-16 10:43 -0500
                Re: How to write a self-referencial TM? Richard Damon <richard@damon-family.org> - 2025-05-16 12:10 -0400
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-17 11:58 +0300
              Re: How to write a self-referencial TM? Richard Damon <richard@damon-family.org> - 2025-05-15 19:37 -0400
              Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-16 10:27 +0300
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-16 10:40 -0500
                Re: How to write a self-referencial TM? "Fred. Zwarts" <F.Zwarts@HetNet.nl> - 2025-05-19 10:21 +0200
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-19 13:39 +0300
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-20 23:41 -0500
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-21 11:47 +0300
                Re: How to write a self-referencial TM? Richard Damon <richard@damon-family.org> - 2025-05-21 07:11 -0400
            Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-16 02:49 +0800
              Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-15 14:15 -0500
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-16 04:08 +0800
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-16 10:45 +0300
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-16 10:47 -0500
                Re: How to write a self-referencial TM? "Fred. Zwarts" <F.Zwarts@HetNet.nl> - 2025-05-16 21:34 +0200
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-16 10:40 +0300
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-16 10:44 -0500
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-17 12:02 +0300
              Re: How to write a self-referencial TM? Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2025-05-16 01:40 +0100
                Re: How to write a self-referencial TM? Richard Heathfield <rjh@cpax.org.uk> - 2025-05-16 01:59 +0100
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-16 09:47 +0800
                Re: How to write a self-referencial TM? Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2025-05-16 03:26 +0100
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-16 19:40 +0800
                Re: How to write a self-referencial TM? Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2025-05-16 16:33 +0100
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-17 03:35 +0800
                Re: How to write a self-referencial TM? Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2025-05-16 23:51 +0100
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-17 11:01 +0800
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-16 22:12 -0500
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-17 11:23 +0800
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-16 22:40 -0500
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-17 11:49 +0800
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-16 22:58 -0500
                Re: How to write a self-referencial TM? Richard Damon <richard@damon-family.org> - 2025-05-17 09:02 -0400
                Re: How to write a self-referencial TM? Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2025-05-17 15:45 +0100
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-18 03:26 +0800
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-17 14:39 -0500
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-18 11:20 +0300
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-19 04:35 +0800
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-18 15:57 -0500
                Re: How to write a self-referencial TM? Richard Damon <richard@damon-family.org> - 2025-05-18 17:45 -0400
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-19 05:46 +0800
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-18 17:09 -0500
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-19 06:35 +0800
                Re: How to write a self-referencial TM? Richard Damon <richard@damon-family.org> - 2025-05-18 19:09 -0400
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-19 07:54 +0800
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-19 13:52 +0300
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-19 13:48 +0300
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-20 23:36 -0500
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-21 11:56 +0300
                Re: How to write a self-referencial TM? André G. Isaak <agisaak@gm.invalid> - 2025-05-18 15:58 -0600
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-18 17:08 -0500
                Re: How to write a self-referencial TM? Richard Damon <richard@damon-family.org> - 2025-05-18 19:19 -0400
                Re: How to write a self-referencial TM? André G. Isaak <agisaak@gm.invalid> - 2025-05-18 21:21 -0600
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-18 23:07 -0500
                Re: How to write a self-referencial TM? "Fred. Zwarts" <F.Zwarts@HetNet.nl> - 2025-05-19 09:54 +0200
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-19 15:29 +0300
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-20 23:33 -0500
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-21 12:03 +0300
                Re: How to write a self-referencial TM? Richard Damon <richard@damon-family.org> - 2025-05-21 07:16 -0400
                Re: How to write a self-referencial TM? "Fred. Zwarts" <F.Zwarts@HetNet.nl> - 2025-05-21 21:43 +0200
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-21 14:49 -0500
                Re: How to write a self-referencial TM? "Fred. Zwarts" <F.Zwarts@HetNet.nl> - 2025-05-23 13:03 +0200
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-19 13:44 +0300
                Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-19 13:41 +0300
                Re: How to write a self-referencial TM? Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2025-05-17 20:46 +0100
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-17 14:55 -0500
                Re: How to write a self-referencial TM? Richard Damon <richard@damon-family.org> - 2025-05-17 16:07 -0400
                Re: How to write a self-referencial TM? Andy Walker <anw@cuboid.co.uk> - 2025-05-16 12:22 +0100
                Re: How to write a self-referencial TM? Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2025-05-16 16:57 +0100
                Re: How to write a self-referencial TM? Andy Walker <anw@cuboid.co.uk> - 2025-05-16 21:04 +0100
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-16 15:38 -0500
                Re: How to write a self-referencial TM? wij <wyniijj5@gmail.com> - 2025-05-17 05:21 +0800
                Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-16 16:40 -0500
                Re: How to write a self-referencial TM? Richard Damon <richard@damon-family.org> - 2025-05-16 20:32 -0400
                Re: How to write a self-referencial TM? Richard Damon <richard@damon-family.org> - 2025-05-16 17:59 -0400
        Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-16 10:24 +0300
          Re: How to write a self-referencial TM? olcott <polcott333@gmail.com> - 2025-05-16 10:37 -0500
  Re: How to write a self-referencial TM? Mikko <mikko.levanto@iki.fi> - 2025-05-15 10:07 +0300

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