Re: complex number in struct form in C

From	glen herrmannsfeldt <gah@ugcs.caltech.edu>
Newsgroups	comp.lang.c
Subject	Re: complex number in struct form in C
Date	2014-12-28 07:28 +0000
Organization	Aioe.org NNTP Server
Message-ID	<m7obf8$op6$1@speranza.aioe.org> (permalink)
References	(6 earlier) <f03e9ap9a4qac9er1qb2hi4dtb5nq00978@4ax.com> <62472149-c09e-42d6-9789-3d62b9b3cdf0@googlegroups.com> <YRjnw.322428$607.90723@fx21.am4> <e7414fe4-cc6d-42f6-968d-76170f8d3172@googlegroups.com> <m7mnob$s2p$1@dont-email.me>

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James Kuyper <jameskuyper@verizon.net> wrote:
> On 12/27/2014 03:22 AM, asetofsymbols@gmail.com wrote:
>> If one has a fixed point number, if I understand right, one has too 
>> a way for check if result is correct... For float not fixed point 
>> one can not be sure... Than one can make errors with fixed point too...

> Could you explain that comment further? I see no inherent reason why
> fixed point formats couldn't implement something similar to a floating
> point NaN.

They could, but traditionally haven't done that.

If might be convenient to use the most negative twos complement
value as a NaN. That would remove the problem with negating it.
It might even be nice to have an exception for operations on that
value, similar to a signaling NaN.

But in the beginning of twos complement computing it wasn't done,
and people got used to hardware not doing it.

Well, partly many early systems used sign magnitude, and then a little
later, ones complement. In those cases, one might have used -0 as
a trap (NaN) representation, but most didn't. When building adders
out of vacuum tubes, anything that made it simpler made it faster
and cheaper.

(Fortran originated on the 36 bit sign magnitude vacuum tube
based IBM 709. Actually, it stores 16 bit (15 plus sign) in 
the 36 bit words.)

-- glen

Thread

complex number in struct form in C Dexterr <dejangru@gmail.com> - 2014-12-21 07:20 -0800
  Re: complex number in struct form in C James Kuyper <jameskuyper@verizon.net> - 2014-12-21 11:30 -0500
    Re: complex number in struct form in C Dexterr <dejangru@gmail.com> - 2014-12-21 08:35 -0800
      Re: complex number in struct form in C "Osmium" <r124c4u102@comcast.net> - 2014-12-21 10:54 -0600
        Re: complex number in struct form in C James Kuyper <jameskuyper@verizon.net> - 2014-12-21 12:00 -0500
          Re: complex number in struct form in C "Osmium" <r124c4u102@comcast.net> - 2014-12-21 11:08 -0600
            Re: complex number in struct form in C Barry Schwarz <schwarzb@dqel.com> - 2014-12-21 10:12 -0800
              Re: complex number in struct form in C "Osmium" <r124c4u102@comcast.net> - 2014-12-21 13:22 -0600
                Re: complex number in struct form in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-21 22:21 +0000
              Re: complex number in struct form in C asetofsymbols@gmail.com - 2014-12-26 11:34 -0800
                Re: complex number in struct form in C "Osmium" <r124c4u102@comcast.net> - 2014-12-26 14:10 -0600
                Re: complex number in struct form in C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-28 07:04 +0000
                Re: complex number in struct form in C BartC <bc@freeuk.com> - 2014-12-28 13:14 +0000
                Re: complex number in struct form in C Robert Wessel <robertwessel2@yahoo.com> - 2014-12-28 10:45 -0600
                Re: complex number in struct form in C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-28 08:56 -0800
                Re: complex number in struct form in C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-29 10:10 +0000
                Re: complex number in struct form in C Kaz Kylheku <kaz@kylheku.com> - 2014-12-29 19:40 +0000
                Re: complex number in struct form in C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-29 20:54 +0000
                Re: complex number in struct form in C BartC <bc@freeuk.com> - 2014-12-29 21:55 +0000
                Re: complex number in struct form in C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-30 03:07 +0000
                Re: complex number in struct form in C BartC <bc@freeuk.com> - 2014-12-30 10:51 +0000
                Re: complex number in struct form in C Rosario193 <Rosario@invalid.invalid> - 2014-12-30 12:15 +0100
                Re: complex number in struct form in C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-30 03:31 -0800
                Re: complex number in struct form in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-30 12:17 +0000
                Re: complex number in struct form in C BartC <bc@freeuk.com> - 2014-12-30 13:18 +0000
                Re: complex number in struct form in C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-30 05:28 -0800
                Re: complex number in struct form in C BartC <bc@freeuk.com> - 2014-12-30 13:53 +0000
                Re: complex number in struct form in C "Osmium" <r124c4u102@comcast.net> - 2014-12-30 08:53 -0600
                Re: complex number in struct form in C "Chris M. Thomasson" <no@spam.invalid> - 2014-12-30 20:05 -0800
                Re: complex number in struct form in C Jeff Higgins <jeff@invalid.invalid> - 2014-12-30 17:40 -0500
                Re: complex number in struct form in C Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-24 08:58 -0700
                Re: complex number in struct form in C Les Cargill <lcargill99@comcast.com> - 2015-03-24 19:41 -0500
                Re: complex number in struct form in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-30 14:59 +0000
                Re: complex number in struct form in C David Thompson <dave.thompson2@verizon.net> - 2015-01-12 15:33 -0500
                Re: complex number in struct form in C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-01-12 22:51 +0000
                Re: complex number in struct form in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-01-12 23:34 +0000
                Re: complex number in struct form in C James Kuyper <jameskuyper@verizon.net> - 2014-12-26 15:25 -0500
                Re: complex number in struct form in C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-28 07:17 +0000
                Re: complex number in struct form in C BartC <bc@freeuk.com> - 2014-12-26 20:49 +0000
                Re: complex number in struct form in C asetofsymbols@gmail.com - 2014-12-27 00:22 -0800
                Re: complex number in struct form in C "Osmium" <r124c4u102@comcast.net> - 2014-12-27 08:25 -0600
                Re: complex number in struct form in C Geoff <geoff@invalid.invalid> - 2014-12-27 10:20 -0800
                Re: complex number in struct form in C "Osmium" <r124c4u102@comcast.net> - 2014-12-27 13:21 -0600
                Re: complex number in struct form in C Geoff <geoff@invalid.invalid> - 2014-12-27 13:11 -0800
                Re: complex number in struct form in C "Osmium" <r124c4u102@comcast.net> - 2014-12-27 15:36 -0600
                Re: complex number in struct form in C Geoff <geoff@invalid.invalid> - 2014-12-27 14:54 -0800
                Re: complex number in struct form in C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-27 15:45 -0800
                Re: complex number in struct form in C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-27 13:40 -0800
                Re: complex number in struct form in C James Kuyper <jameskuyper@verizon.net> - 2014-12-28 06:50 -0500
                Re: complex number in struct form in C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-28 04:25 -0800
                Re: complex number in struct form in C James Kuyper <jameskuyper@verizon.net> - 2014-12-28 06:44 -0500
                Re: complex number in struct form in C Richard Damon <Richard@Damon-Family.org> - 2014-12-28 08:33 -0500
                Re: complex number in struct form in C James Kuyper <jameskuyper@verizon.net> - 2014-12-27 11:46 -0500
                Re: complex number in struct form in C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-28 07:28 +0000
                Re: complex number in struct form in C Kaz Kylheku <kaz@kylheku.com> - 2014-12-27 17:23 +0000
            Re: complex number in struct form in C James Kuyper <jameskuyper@verizon.net> - 2014-12-21 14:37 -0500
          Re: complex number in struct form in C Keith Thompson <kst-u@mib.org> - 2014-12-21 12:37 -0800
          Re: complex number in struct form in C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-22 00:54 +0000
      Re: complex number in struct form in C James Kuyper <jameskuyper@verizon.net> - 2014-12-21 11:54 -0500
      Re: complex number in struct form in C Vincenzo Mercuri <nomail@yahoo.it> - 2014-12-21 18:07 +0100
        Re: complex number in struct form in C Dexterr <dejangru@gmail.com> - 2014-12-21 10:37 -0800
          Re: complex number in struct form in C "Chris M. Thomasson" <no@spam.invalid> - 2014-12-21 10:55 -0800
          Re: complex number in struct form in C raltbos@xs4all.nl (Richard Bos) - 2014-12-22 12:15 +0000
            Re: complex number in struct form in C Dexterr <dejangru@gmail.com> - 2014-12-22 05:51 -0800
              Re: complex number in struct form in C BartC <bc@freeuk.com> - 2014-12-22 14:01 +0000
                Re: complex number in struct form in C Keith Thompson <kst-u@mib.org> - 2014-12-22 08:02 -0800
            Re: complex number in struct form in C Keith Thompson <kst-u@mib.org> - 2014-12-22 08:03 -0800
    Re: complex number in struct form in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-21 22:27 +0000
  Re: complex number in struct form in C "Chris M. Thomasson" <no@spam.invalid> - 2014-12-21 10:51 -0800
    Re: complex number in struct form in C Dexterr <dejangru@gmail.com> - 2014-12-21 11:14 -0800
  Re: complex number in struct form in C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-21 17:17 -0800

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