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Re: MISRA C

From Alan Mackenzie <acm@muc.de>
Newsgroups comp.lang.c
Subject Re: MISRA C
Date 2026-09-28 12:17 +0000
Organization muc.de e.V.
Message-ID <119dltm$1vnn$1@news.muc.de> (permalink)
References (10 earlier) <1195qr8$2aem2$1@dont-email.me> <1195u2r$16ah$1@news.muc.de> <119612d$2aem2$2@dont-email.me> <11962u0$16ah$2@news.muc.de> <119dhqt$1uucd$1@dont-email.me>

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Janis Papanagnou <janis_papanagnou+ng@hotmail.com> wrote:
> On 2026-09-25 17:10, Alan Mackenzie wrote:

[ .... ]

> > Yes, it was the Ackermann function I had in mind (though I'd forgotten
> > its name).  It's a function of two natural number arguments.  Simply
> > making both arguments the same gives a function of one argument.

> > [...]

> > This function can't be calculated iteratively, since there's no
> > non-recursive way of calculating how big the requisite static arrays
> > would have to be.  Or something like that.

> Franky, I'm too lazy now to derive the iterative form myself.

I understand the laziness.  ;-)

> But if you're not convinced by the principle considerations it's fairly
> easy to ask an AI to create some C-code, verify that it has no
> recursive calls, and check its results. - The code that the AI had
> provided to me seems to work well.[*]

David Brown clarified on Saturday what I really should have said, had I
been on the ball with computing theory.  The Ackermann function is not
_primitive recursive_.  It can't be calculated in any bounded amount of
storage which can be determined at the start of the calculation.

Your iterative solution will be continually increasing the amount of
store it uses as it goes along.  A normal way of doing this implicitly
is with recursion.

I don't think we're really in disagreement about anything substantial
here.

> Janis

> [*] http://volatile.gridbug.de/ack_iterative.c
> (only slightly adjusted version to accept command line arguments)

-- 
Alan Mackenzie (Nuremberg, Germany).

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MISRA C (was: buckle-up ....) Alan Mackenzie <acm@muc.de> - 2026-09-25 10:01 +0000
  Re: MISRA C Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-09-25 14:52 +0200
    Re: MISRA C Alan Mackenzie <acm@muc.de> - 2026-09-25 13:48 +0000
      Re: MISRA C Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-09-25 16:39 +0200
        Re: MISRA C Alan Mackenzie <acm@muc.de> - 2026-09-25 15:10 +0000
          Re: MISRA C bart <bc@freeuk.com> - 2026-09-25 16:57 +0100
          Re: MISRA C Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-09-25 11:42 -0700
            Re: MISRA C Alan Mackenzie <acm@muc.de> - 2026-09-25 20:21 +0000
              Re: MISRA C Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-09-25 14:05 -0700
                Re: MISRA C David Brown <david.brown@hesbynett.no> - 2026-09-26 08:43 +0200
                Re: MISRA C Alan Mackenzie <acm@muc.de> - 2026-09-26 17:55 +0000
                Re: MISRA C Ben Bacarisse <ben@bsb.me.uk> - 2026-10-03 23:55 +0100
                Re: MISRA C David Brown <david.brown@hesbynett.no> - 2026-10-04 16:10 +0200
                Re: MISRA C Ben Bacarisse <ben@bsb.me.uk> - 2026-10-05 01:22 +0100
                Re: MISRA C David Brown <david.brown@hesbynett.no> - 2026-10-05 07:59 +0200
                Re: MISRA C Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-05 01:23 -0700
                Re: MISRA C Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-05 01:24 -0700
                Re: MISRA C antispam@fricas.org (Waldek Hebisch) - 2026-10-05 09:02 +0000
                Re: MISRA C Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-10-05 12:07 +0200
                Re: MISRA C Ben Bacarisse <ben@bsb.me.uk> - 2026-10-05 15:29 +0100
                Re: MISRA C antispam@fricas.org (Waldek Hebisch) - 2026-10-05 20:29 +0000
                Re: MISRA C Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-06 22:13 -0700
                Re: MISRA C Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-06 22:14 -0700
          Re: MISRA C Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-09-27 10:52 -0700
          Re: MISRA C Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-09-28 13:08 +0200
            Re: MISRA C bart <bc@freeuk.com> - 2026-09-28 13:07 +0100
            Re: MISRA C David Brown <david.brown@hesbynett.no> - 2026-09-28 14:08 +0200
              Re: MISRA C Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-09-28 14:28 +0200
            Re: MISRA C Alan Mackenzie <acm@muc.de> - 2026-09-28 12:17 +0000
              Re: MISRA C Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-09-28 14:40 +0200
          Re: MISRA C "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-09-30 10:21 -0700
            Re: MISRA C Alan Mackenzie <acm@muc.de> - 2026-09-30 19:57 +0000
              Re: MISRA C "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-09-30 13:09 -0700
                Re: MISRA C David Brown <david.brown@hesbynett.no> - 2026-10-01 08:47 +0200
                Re: MISRA C "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-10-01 15:18 -0700
      Re: MISRA C Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-09-27 04:58 +0800
  Re: MISRA C David Brown <david.brown@hesbynett.no> - 2026-09-25 17:02 +0200
  Re: MISRA C "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-09-26 15:37 -0700

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