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Re: C/C++ pitfalls related to 64-bits (unsigned long & double)

From glen herrmannsfeldt <gah@ugcs.caltech.edu>
Newsgroups comp.lang.c, comp.lang.c++
Subject Re: C/C++ pitfalls related to 64-bits (unsigned long & double)
Date 2012-02-13 21:52 +0000
Organization Aioe.org NNTP Server
Message-ID <jhc0mt$4os$1@speranza.aioe.org> (permalink)
References <2d5ceb71-98bb-440a-be68-69c4c736532a@s13g2000yqe.googlegroups.com> <jhb2b8$cmt$1@dont-email.me> <jhb2h2$cmt$2@dont-email.me>

Cross-posted to 2 groups.

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In comp.lang.c++ Eric Sosman <esosman@ieee-dot-org.invalid> wrote:
> On 2/13/2012 8:14 AM, Eric Sosman wrote:
>> [...] Since hardware that offers 64 bits of precision in the
>> floating-point format used for `double', some loss of precision in
>> `b = a' must be expected.

>     Oh, drat.  There was supposed to be an "is fairly rare" just
> before the comma ...

x87 hardware isn't that rare. Depending on the implementation,
the compiler might do the calculation in temporary real form,
with all 64 bits.

But, yes, the usual double is 64 total bits, so fewer than 64
for the significand. As far as I know, though, there is no
restriction in C or C++ against a larger double, such as
a 64 bit float and 128 bit double.

-- glen

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Thread

C/C++ pitfalls related to 64-bits (unsigned long & double) Alex Vinokur <alex.vinokur@gmail.com> - 2012-02-13 04:41 -0800
  Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Leigh Johnston <leigh@i42.co.uk> - 2012-02-13 12:49 +0000
    Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Alex Vinokur <alex.vinokur@gmail.com> - 2012-02-13 04:59 -0800
      Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Leigh Johnston <leigh@i42.co.uk> - 2012-02-13 13:07 +0000
  Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Goran <goran.pusic@gmail.com> - 2012-02-13 04:54 -0800
    Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Alex Vinokur <alex.vinokur@gmail.com> - 2012-02-13 05:00 -0800
    Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-13 13:27 +0000
    Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Goran <goran.pusic@gmail.com> - 2012-02-13 07:14 -0800
  Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-13 08:14 -0500
    Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-13 08:17 -0500
      Re: C/C++ pitfalls related to 64-bits (unsigned long & double) glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-02-13 21:52 +0000
        Re: C/C++ pitfalls related to 64-bits (unsigned long & double) James Kuyper <jameskuyper@verizon.net> - 2012-02-13 17:08 -0500
        Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-13 20:44 -0500
  Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-13 13:16 +0000
    Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-13 11:18 -0700
      Re: C/C++ pitfalls related to 64-bits (unsigned long & double) "MikeWhy" <boat042-nospam@yahoo.com> - 2012-02-13 15:18 -0600
        Re: C/C++ pitfalls related to 64-bits (unsigned long & double) James Kuyper <jameskuyper@verizon.net> - 2012-02-13 16:26 -0500
          Re: C/C++ pitfalls related to 64-bits (unsigned long & double) "MikeWhy" <boat042-nospam@yahoo.com> - 2012-02-13 16:05 -0600
            Re: C/C++ pitfalls related to 64-bits (unsigned long & double) James Kuyper <jameskuyper@verizon.net> - 2012-02-13 17:13 -0500
              Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-13 23:35 +0000
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-13 17:25 -0700
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-14 01:45 +0000
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-13 18:55 -0700
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Miles Bader <miles@gnu.org> - 2012-02-14 11:51 +0900
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-14 03:13 +0000
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-13 20:39 -0700
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Miles Bader <miles@gnu.org> - 2012-02-14 13:25 +0900
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-13 23:22 -0700
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) "MikeWhy" <boat042-nospam@yahoo.com> - 2012-02-14 02:56 -0600
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-14 09:13 -0700
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) "MikeWhy" <boat042-nospam@yahoo.com> - 2012-02-14 11:16 -0600
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-14 12:27 -0700
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-13 23:04 -0500
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Miles Bader <miles@gnu.org> - 2012-02-14 14:00 +0900
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Robert Wessel <robertwessel2@yahoo.com> - 2012-02-14 00:45 -0600
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-02-14 14:22 +0000
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Robert Wessel <robertwessel2@yahoo.com> - 2012-02-14 13:06 -0600
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-14 12:40 -0700
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) James Kuyper <jameskuyper@verizon.net> - 2012-02-13 23:05 -0500
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Miles Bader <miles@gnu.org> - 2012-02-14 14:01 +0900
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Keith Thompson <kst-u@mib.org> - 2012-02-14 03:01 -0800
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Lowell Gilbert <lgusenet@be-well.ilk.org> - 2012-02-14 12:53 -0500
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) James Kuyper <jameskuyper@verizon.net> - 2012-02-14 14:39 -0500
            Re: C/C++ pitfalls related to 64-bits (unsigned long & double) jgk@panix.com (Joe keane) - 2012-02-14 20:45 +0000
              Re: C/C++ pitfalls related to 64-bits (unsigned long & double) glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-02-14 22:57 +0000
              Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Keith Thompson <kst-u@mib.org> - 2012-02-14 15:38 -0800
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-02-15 00:22 +0000
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Robert Wessel <robertwessel2@yahoo.com> - 2012-02-15 00:39 -0600
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-02-15 08:00 +0000
      Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-13 22:00 +0000
        Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-13 17:04 -0700
          Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-13 16:15 -0800
          Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-14 00:46 +0000
            Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-13 18:31 -0700
              Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-13 18:41 -0700
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-14 02:33 +0000
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-13 20:20 -0700
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-14 03:26 +0000
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-13 20:49 -0700
              Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Robert Wessel <robertwessel2@yahoo.com> - 2012-02-14 00:24 -0600
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-13 23:42 -0700
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) James Kuyper <jameskuyper@verizon.net> - 2012-02-14 06:48 -0500
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-14 13:51 +0000
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-14 08:42 -0700
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-02-14 19:58 +0000
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-02-14 14:27 +0000
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) BGB <cr88192@hotmail.com> - 2012-02-14 09:10 -0700
                Re: C/C++ pitfalls related to 64-bits (unsigned long & double) glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-02-14 20:02 +0000
  Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Noob <root@127.0.0.1> - 2012-02-13 15:22 +0100
  Re: C/C++ pitfalls related to 64-bits (unsigned long & double) legalize+jeeves@mail.xmission.com (Richard) - 2012-02-13 18:49 +0000
    Re: C/C++ pitfalls related to 64-bits (unsigned long & double) James Kuyper <jameskuyper@verizon.net> - 2012-02-13 13:55 -0500
      Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Juha Nieminen <nospam@thanks.invalid> - 2012-02-13 19:14 +0000
  Re: C/C++ pitfalls related to 64-bits (unsigned long & double) Barry Schwarz <schwarzb@dqel.com> - 2012-02-13 12:14 -0800

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