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Groups > comp.lang.c > #176878

Re: bart again (UCX64)

From Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups comp.lang.c
Subject Re: bart again (UCX64)
Date 2023-10-01 11:03 -0700
Organization A noiseless patient Spider
Message-ID <86a5t2dxu2.fsf@linuxsc.com> (permalink)
References (11 earlier) <60jMM.5116$quJ8.2754@fx18.iad> <861qevmfym.fsf@linuxsc.com> <87edivkyfu.fsf@nosuchdomain.example.com> <86zg1gjlf5.fsf@linuxsc.com> <87il84158n.fsf@nosuchdomain.example.com>

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Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

> Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
>
>> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>>
>>> Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
>>>
>>>> scott@slp53.sl.home (Scott Lurndal) writes:
>>>>
>>>>> NaN is a term of art referring specifically to the IEEE
>>>>> floating point standard.   I've never seen "NaN" used in any
>>>>> other context (albeit some use it to refer to their grandmother :-).
>>>>
>>>> The C standard uses (and also defines) the word NaN as a generic
>>>> term applicable to floating-point representations in general.  In
>>>> section 5.2.4.2.2 paragraph 3, the C standard says this
>>>>
>>>>     A /NaN/ is an encoding signifying Not-a-Number.
>>>>
>>>> with the slant characters meaning italics, which indicates a
>>>> definition.  The same paragraph gives generic definitions for
>>>> the more specialized terms "quiet NaN" and "signaling NaN".
>>>>
>>>> There is a footnote that mentions the IEEE floating-point
>>>> standard, but makes clear that terms for the various kinds of NaN
>>>> can refer to values in other floating-point systems that have
>>>> similar behavior.
>>>
>>> Agreed, the C standard is careful not to assume that floating-point
>>> systems other than IEEE do or do not have NaNs.
>>>
>>> In the real world, as far as I can tell, IEEE happens to be the
>>> only floating-point system that has NaNs.
>>
>> That question is best left to a different newsgroup.  In any
>> case it makes no difference to my statement, which is only
>> about how the term NaN is used.
>
> You'll note that I started by saying I agreed with you.
>
> I'd say that since the C standard has a lot to say about floating-point,
> including NaNs and optional support for IEEE (IEC 60559) floating-point,
> it's a relevant issue.

I don't know what it is you think your comments are relevant to.
I don't see how they are relevant to what I said in my earlier
posting.

>>> IEEE introduced NaNs
>>> in 1985, and the introduction of the IEEE standard inhibited the
>>> creation of other floating-point formats.  (That's not *quite*
>>> true;  apparently at least some implementations of "posits" provide
>>> NaNs.  But I don't think any C implementation uses posits as its
>>> floating-point representation, and it might not be possible for a
>>> conforming implementation to do so.)
>>
>> A surprising statement.  What is it about posits that make
>> them impossible for a conforming C implementation?  TTBOMK
>> the C standard allows nearly unlimited latitude for how
>> floating-point numbers and operations work in C.  For the
>> record I know very little about posits.
>
> Posits, as I understand them, have a dynamically varying number of
> exponent bits.  That seems inconsistent with the floating point model
> described in N1570 5.2.4.2.2 (<float.h>).

The model you mention is used to define "the characteristics of
floating types", where "characteristics" is understood to be the
preprocessor-symbol numerical limits defined in that section.  There
is nothing in the C standard that requires the representation of
floating types to match the description outlined in model, or to "be
consistent" with it.  There is a footnote in the first paragraph of
5.2.4.2.2;  it says

   The floating-point model is intended to clarify the description
   of each floating-point characteristic and does not require the
   floating-point arithmetic of the implementation to be identical.

So I still don't know why you think a conforming C implementation
couldn't use posits, or some other similar scheme where the
number of significand bits varies depending on the exponent, as
its representation for floating types.

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Re: bart again (UCX64) candycane@f172.n1.z21.fsxnet (candycane) - 2023-09-06 19:53 +1300
  Re: bart again (UCX64) Richard Damon <Richard@Damon-Family.org> - 2023-09-07 12:00 -0700
    Re: bart again (UCX64) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-09-07 16:33 -0700
      Re: bart again (UCX64) Richard Damon <Richard@Damon-Family.org> - 2023-09-07 20:55 -0700
        Re: bart again (UCX64) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-09-07 22:16 -0700
          Re: bart again (UCX64) Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-08 07:09 +0000
            Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-08 10:10 +0200
              Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-08 01:30 -0700
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-08 11:26 +0200
                Re: bart again (UCX64) Bart <bc@freeuk.com> - 2023-09-08 10:44 +0100
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-08 13:26 +0200
                Re: bart again (UCX64) Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-09 01:57 +0000
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-09 18:36 +0200
                Re: bart again (UCX64) Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-09 18:19 +0000
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-10 13:28 +0200
                Re: bart again (UCX64) Bart <bc@freeuk.com> - 2023-09-10 13:20 +0100
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-10 15:19 +0200
                Re: bart again (UCX64) Bart <bc@freeuk.com> - 2023-09-10 16:07 +0100
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-10 18:33 +0200
                Re: bart again (UCX64) Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-10 15:44 +0000
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-10 18:36 +0200
                Re: bart again (UCX64) Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-09 01:48 +0000
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-09 19:04 +0200
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-08 02:47 -0700
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-08 16:03 +0200
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-08 16:06 -0700
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-09 01:52 +0100
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-08 18:16 -0700
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-09 21:31 +0100
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-10 12:03 +0200
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-10 21:36 -0700
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-11 08:51 +0200
                Re: bart again (UCX64) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-09-10 23:59 -0700
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-11 01:01 -0700
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-11 11:17 +0200
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-11 03:16 -0700
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-11 14:58 +0200
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-11 06:35 -0700
                Re: bart again (UCX64) Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-11 14:13 +0000
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-11 16:24 +0200
                Re: bart again (UCX64) Bart <bc@freeuk.com> - 2023-09-11 14:55 +0100
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-11 16:42 +0200
                Re: bart again (UCX64) Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-11 14:29 +0000
                Re: bart again (UCX64) Bart <bc@freeuk.com> - 2023-09-11 11:25 +0100
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-11 03:59 -0700
                Re: bart again (UCX64) Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-11 13:57 +0000
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-11 09:52 -0700
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-11 16:07 +0200
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-11 16:26 +0100
                Re: bart again (UCX64) Bart <bc@freeuk.com> - 2023-09-11 16:47 +0100
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-11 19:14 +0200
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-11 22:30 +0100
                Re: bart again (UCX64) Bart <bc@freeuk.com> - 2023-09-11 23:07 +0100
                Re: bart again (UCX64) scott@slp53.sl.home (Scott Lurndal) - 2023-09-11 23:31 +0000
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-12 09:18 +0200
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-12 03:01 +0100
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-11 10:08 -0700
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-11 23:18 +0100
                Re: bart again (UCX64) Bart <bc@freeuk.com> - 2023-09-11 23:37 +0100
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-11 15:46 -0700
                Re: bart again (UCX64) scott@slp53.sl.home (Scott Lurndal) - 2023-09-11 23:40 +0000
                Re: bart again (UCX64) Bart <bc@freeuk.com> - 2023-09-12 01:50 +0100
                Re: bart again (UCX64) Richard Damon <Richard@Damon-Family.org> - 2023-09-11 17:59 -0700
                Re: bart again (UCX64) scott@slp53.sl.home (Scott Lurndal) - 2023-09-12 01:03 +0000
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-12 02:39 +0100
                Re: bart again (UCX64) Bart <bc@freeuk.com> - 2023-09-12 11:28 +0100
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-12 14:49 +0100
                Re: bart again (UCX64) Bart <bc@freeuk.com> - 2023-09-12 15:18 +0100
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-12 03:58 +0100
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-12 02:25 -0700
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-12 16:17 +0100
                Re: bart again (UCX64) Bart <bc@freeuk.com> - 2023-09-12 17:28 +0100
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-12 21:07 +0200
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-13 03:01 +0100
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-13 09:38 +0200
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-13 10:00 +0200
                Re: bart again (UCX64) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-09-19 05:22 -0700
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-19 14:29 +0100
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-13 13:35 +0100
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-13 20:48 +0100
                Re: bart again (UCX64) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-09-19 05:53 -0700
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-12 09:33 -0700
                Re: bart again (UCX64) scott@slp53.sl.home (Scott Lurndal) - 2023-09-12 16:48 +0000
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-12 10:57 -0700
                Re: bart again (UCX64) scott@slp53.sl.home (Scott Lurndal) - 2023-09-12 18:07 +0000
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-12 21:23 +0200
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-13 02:07 -0700
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-13 12:43 +0200
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-13 04:04 -0700
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-13 14:07 +0200
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-13 01:47 -0700
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-13 13:02 +0200
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-13 04:45 -0700
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-13 14:36 +0200
                Re: bart again (UCX64) scott@slp53.sl.home (Scott Lurndal) - 2023-09-13 13:43 +0000
                Re: bart again (UCX64) James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-09-13 11:10 -0400
                Re: bart again (UCX64) Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-13 17:12 +0000
                [meta] spam in thread Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-13 11:22 -0700
                Re: [meta] spam in thread Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-13 18:40 +0000
                Re: [meta] spam in thread Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-13 11:48 -0700
                Re: [meta] spam in thread David Brown <david.brown@hesbynett.no> - 2023-09-13 21:01 +0200
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-13 19:58 +0100
                Re: bart again (UCX64) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-09-18 12:36 -0700
                Re: bart again (UCX64) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-09-18 13:40 -0700
                Re: bart again (UCX64) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-09-20 19:43 -0700
                Re: bart again (UCX64) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-09-20 20:14 -0700
                Re: bart again (UCX64) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-09-20 22:10 -0700
                Re: bart again (UCX64) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-10-01 11:03 -0700
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-13 07:39 -0700
                Re: bart again (UCX64) scott@slp53.sl.home (Scott Lurndal) - 2023-09-13 15:18 +0000
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-13 18:39 +0200
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-13 15:44 +0100
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-13 08:42 -0700
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-13 22:35 +0100
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-13 18:49 +0200
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-11 15:40 -0700
                Re: bart again (UCX64) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-12 03:36 +0100
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-12 12:58 +0200
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-12 12:49 +0200
                Re: bart again (UCX64) Bart <bc@freeuk.com> - 2023-09-12 12:52 +0100
                Re: bart again (UCX64) Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2023-09-12 05:22 -0700
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-12 15:05 +0200
                Re: bart again (UCX64) Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-09 02:17 +0000
                Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-10 14:44 +0200
                Re: bart again (UCX64) scott@slp53.sl.home (Scott Lurndal) - 2023-09-08 14:36 +0000
                Re: bart again (UCX64) Kaz Kylheku <864-117-4973@kylheku.com> - 2023-09-09 01:50 +0000
                Re: bart again (UCX64) scott@slp53.sl.home (Scott Lurndal) - 2023-09-09 15:40 +0000
          Re: bart again (UCX64) David Brown <david.brown@hesbynett.no> - 2023-09-08 09:57 +0200
          Re: bart again (UCX64) Richard Damon <Richard@Damon-Family.org> - 2023-09-09 10:23 -0700

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