Mod gives negative remainders

[Offtopic]

Binary package hint: gcalctool

By the mathematical definition of the division algorithm ( n = q.d + r ; 0 <= r < d ), the reminder of a division can never be a negative integer.

More information: http://en.wikipedia.org/wiki/Modular_arithmetic

ProblemType: Bug
Architecture: amd64
Date: Sun Jan 20 19:32:28 2008
DistroRelease: Ubuntu 7.10
ExecutablePath: /usr/bin/gcalctool
NonfreeKernelModules: fglrx
Package: gcalctool 5.20.2-0ubuntu1
PackageArchitecture: amd64
ProcCmdline: gcalctool
ProcCwd: /home/offtopic
ProcEnviron:
 PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
 LANG=en_CA.UTF-8
 SHELL=/bin/bash
SourcePackage: gcalctool
Uname: Linux morrocoy 2.6.22-14-generic #1 SMP Tue Dec 18 05:28:27 UTC 2007 x86_64 GNU/Linux

[Greg Grossmeier (greg.grossmeier)]

Can you please provide a specific set of steps to reproduce this problem? With a couple simple tries I couldn't reproduce it.

Thanks!

[Offtopic (usednick)]

Use the Scientific mode (View -> Scientific ; Crtl+S)
Try to do any mod operation with a negative dividend and a positive divisor. (The Mod button is just beside the Acc. button)
Ex: -20 Mod 9 yields -2 on gcalctool, while by definition it should be 7.

Offtopic.

[Greg Grossmeier (greg.grossmeier)]

Reported upstream: http://bugzilla.gnome.org/show_bug.cgi?id=511052

[Greg Grossmeier (greg.grossmeier)]

Quote from upstream:

====
The one thing that might still be wrong is something like:

5 mod -4

gcalctool (with or without this patch) gives an answer 0f 1

qalculate gives and answer of -3. I'm not sure how it got it.

Needs to be investigated further.

Greg, could you please ask Offtopic what s/he thinks the
answer to this should be (and how they derived it)?

Thanks.
====

[Greg Grossmeier (greg.grossmeier)]

Offtopic,

Sorry, I relayed the question too quickly. The developer figured it out.

There is a patch for left-to-right precedence, but not arithmetic yet. But they are working on it as we speak.

[Greg Grossmeier (greg.grossmeier)]

The developers have fixed this issue in their development version. Look for the changes in the next release of gcalctool.

[Offtopic (usednick)]

Thanks for your work and attention guys!

Regards,
Offtopic.

[Christophe Sauthier (christophe.sauthier)]

The fix is released in, at least the current hardy version (5.21.92)

[Christophe Sauthier (christophe.sauthier)]

Reput the old assignee, that I remove unwillingly... sorry...