Re: C arithmetic question.

From	Ike Naar <ike@sverige.freeshell.org>
Newsgroups	comp.lang.c
Subject	Re: C arithmetic question.
Date	2012-01-19 08:41 +0000
Organization	A noiseless patient Spider
Message-ID	<slrn3vfsjhflpb.8kc.ike@sverige.freeshell.org> (permalink)
References	<rubrum-90D33D.10325618012012@news.albasani.net> <0eb6c644-ac1e-4de6-8d8a-c1978a8ce255@b10g2000pbd.googlegroups.com> <rubrum-05D6FB.15510218012012@news.albasani.net> <1bhazss041.fsf@pfeifferfamily.net> <rubrum-72E0E9.23142118012012@news.albasani.net>

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On 2012-01-19, Michael Press <rubrum@pacbell.net> wrote:
> In article <1bhazss041.fsf@pfeifferfamily.net>,
>  Joe Pfeiffer <pfeiffer@cs.nmsu.edu> wrote:
>
>> Michael Press <rubrum@pacbell.net> writes:
>> 
>> > In article 
>> > <0eb6c644-ac1e-4de6-8d8a-c1978a8ce255@b10g2000pbd.googlegroups.com>,
>> >  Peter Nilsson <airia@acay.com.au> wrote:
>> >
>> >> Michael Press <rub...@pacbell.net> wrote:
>> >> > [-58ul % 37 == 23]
>> >> > ...
>> >> > 23 cannot be the right answer because
>> >> > 37 does not divide -58 - 23 = -81.
>> >> 
>> >> You have the explanation in the other posts. I just wanted to say...
>> >> 
>> >> > Is this a bug in the compiler or a problem with the C standard?
>> >> 
>> >> From experience, I can tell you that you're in for a lifetime of pain
>> >> and embarrassment if these continue to be your first thoughts every
>> >> time you encounter unexplained output!
>> >
>> > I am not embarrassed; the pain is slight.
>> > The lesson is to use a library designed to
>> > do arithmetic rather than expecting it from C.
>> 
>> Of course, there are several lessons possible from any example.  But I
>> think "understand how unsigneds work" might be a better one in this
>> case.
>
> I prefer mine. C does not have a consistent approach to arithmetic.
> The soi disant mod operator violates the fundamental law:
>
> x = y (mod m) if and only if x - y  is divisible by m.

The mod operator does not violate that law.
Your problem is not with the mod operator, it's
that the numbers that are given to the mod operator
are not what you think they are.

Thread

C arithmetic question. Michael Press <rubrum@pacbell.net> - 2012-01-18 10:32 -0800
  Re: C arithmetic question. James Kuyper <jameskuyper@verizon.net> - 2012-01-18 14:03 -0500
    Re: C arithmetic question. TheGunslinger <mikiesrunsbaal.sec@sbcglobal.net> - 2012-01-18 19:30 -0800
      Re: C arithmetic question. James Kuyper <jameskuyper@verizon.net> - 2012-01-19 08:10 -0500
  Re: C arithmetic question. Markus Wichmann <nullplan@gmx.net> - 2012-01-18 21:14 +0100
    Re: C arithmetic question. "BartC" <bc@freeuk.com> - 2012-01-19 10:44 +0000
      Re: C arithmetic question. Seebs <usenet-nospam@seebs.net> - 2012-01-21 21:32 +0000
  Re: C arithmetic question. Peter Nilsson <airia@acay.com.au> - 2012-01-18 13:51 -0800
    Re: C arithmetic question. Michael Press <rubrum@pacbell.net> - 2012-01-18 15:51 -0800
      Re: C arithmetic question. James Kuyper <jameskuyper@verizon.net> - 2012-01-18 20:50 -0500
        Re: C arithmetic question. Michael Press <rubrum@pacbell.net> - 2012-01-20 12:41 -0800
          Re: C arithmetic question. Keith Thompson <kst-u@mib.org> - 2012-01-20 14:11 -0800
            Re: C arithmetic question. gazelle@shell.xmission.com (Kenny McCormack) - 2012-01-20 22:43 +0000
          Re: C arithmetic question. James Kuyper <jameskuyper@verizon.net> - 2012-01-20 17:19 -0500
            Re: C arithmetic question. James Kuyper <jameskuyper@verizon.net> - 2012-01-20 17:32 -0500
              And jacob navia <jacob@spamsink.net> - 2012-01-20 23:52 +0100
                Re: And Markus Wichmann <nullplan@gmx.net> - 2012-01-21 19:23 +0100
                Re: And Keith Thompson <kst-u@mib.org> - 2012-01-21 13:20 -0800
                Re: And jacob navia <jacob@spamsink.net> - 2012-01-21 23:02 +0100
                Re: And Markus Wichmann <nullplan@gmx.net> - 2012-01-22 15:24 +0100
                Re: And Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-22 15:40 +0000
                Re: And blp@cs.stanford.edu (Ben Pfaff) - 2012-01-21 11:02 -0800
          Re: C arithmetic question. Rui Maciel <rui.maciel@gmail.com> - 2012-01-24 18:53 +0000
      Re: C arithmetic question. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-19 02:09 +0000
      Re: C arithmetic question. Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2012-01-18 23:00 -0700
        Re: C arithmetic question. Michael Press <rubrum@pacbell.net> - 2012-01-18 23:14 -0800
          Re: C arithmetic question. Ike Naar <ike@sverige.freeshell.org> - 2012-01-19 08:41 +0000
            Re: C arithmetic question. Michael Press <rubrum@pacbell.net> - 2012-01-20 12:43 -0800
              Re: C arithmetic question. Kaz Kylheku <kaz@kylheku.com> - 2012-01-20 22:17 +0000
                Re: C arithmetic question. Michael Press <rubrum@pacbell.net> - 2012-01-21 00:12 -0800
              Re: C arithmetic question. Seebs <usenet-nospam@seebs.net> - 2012-01-21 21:32 +0000
                Re: C arithmetic question. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-21 23:21 +0000
                Re: C arithmetic question. Robert Wessel <robertwessel2@yahoo.com> - 2012-01-22 00:48 -0600
                Re: C arithmetic question. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-22 11:45 +0000
                Re: C arithmetic question. Robert Wessel <robertwessel2@yahoo.com> - 2012-01-22 21:46 -0600
                Re: C arithmetic question. Kaz Kylheku <kaz@kylheku.com> - 2012-01-23 04:17 +0000
                Re: C arithmetic question. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-23 11:19 +0000
                Re: C arithmetic question. Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-26 10:41 -0800
                Re: C arithmetic question. Seebs <usenet-nospam@seebs.net> - 2012-01-23 07:58 +0000
                Re: C arithmetic question. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-23 11:06 +0000
                Re: C arithmetic question. James Kuyper <jameskuyper@verizon.net> - 2012-01-23 07:03 -0500
                Re: C arithmetic question. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-23 17:27 +0000
          Re: C arithmetic question. Keith Thompson <kst-u@mib.org> - 2012-01-19 02:38 -0800
            Re: C arithmetic question. Dr Nick <3-nospam@temporary-address.org.uk> - 2012-01-20 07:30 +0000
          Re: C arithmetic question. Nomen Nescio <nobody@dizum.com> - 2012-01-19 12:28 +0100
            Re: C arithmetic question. Michael Press <rubrum@pacbell.net> - 2012-01-20 12:44 -0800
              Re: C arithmetic question. 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-20 13:14 -0800
          Re: C arithmetic question. James Kuyper <jameskuyper@verizon.net> - 2012-01-19 08:45 -0500
          Re: C arithmetic question. Chad <cdalten@gmail.com> - 2012-01-24 08:14 -0800
            Re: C arithmetic question. James Kuyper <jameskuyper@verizon.net> - 2012-01-24 12:15 -0500
              Re: C arithmetic question. Chad <cdalten@gmail.com> - 2012-01-24 09:26 -0800
                Re: C arithmetic question. James Kuyper <jameskuyper@verizon.net> - 2012-01-24 12:39 -0500
                Re: C arithmetic question. Chad <cdalten@gmail.com> - 2012-01-24 10:03 -0800
                Re: C arithmetic question. James Kuyper <jameskuyper@verizon.net> - 2012-01-24 13:23 -0500
                Re: C arithmetic question. Chad <cdalten@gmail.com> - 2012-01-24 10:40 -0800
                Re: C arithmetic question. James Kuyper <jameskuyper@verizon.net> - 2012-01-24 14:35 -0500
                Re: C arithmetic question. Chad <cdalten@gmail.com> - 2012-01-24 12:04 -0800
                Re: C arithmetic question. Chad <cdalten@gmail.com> - 2012-01-24 12:02 -0800
                Re: C arithmetic question. Kleuske <kleuske@nowhere.net> - 2012-01-24 20:26 +0000
                Re: C arithmetic question. Chad <cdalten@gmail.com> - 2012-01-24 13:45 -0800
                Re: C arithmetic question. James Kuyper <jameskuyper@verizon.net> - 2012-01-24 15:40 -0500
                Re: C arithmetic question. Chad <cdalten@gmail.com> - 2012-01-24 12:09 -0800
      Re: C arithmetic question. Rui Maciel <rui.maciel@gmail.com> - 2012-01-24 18:48 +0000
    Re: C arithmetic question. "osmium" <r124c4u102@comcast.net> - 2012-01-19 08:12 -0600
  Re: C arithmetic question. Geoff <geoff@invalid.invalid> - 2012-01-20 15:33 -0800
    Re: C arithmetic question. Kleuske <kleuske@nowhere.net> - 2012-01-27 08:17 +0000
      Re: C arithmetic question. Geoff <geoff@invalid.invalid> - 2012-01-27 13:37 -0800

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