From bug-octave-request at bevo dot che dot wisc dot edu Wed Jan 29 21:42:19 2003
Subject: Re: Trivial 0ctave bug
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Mirek Kwasniak <mirek at zind dot ikem dot pwr dot wroc dot pl>
Cc: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>,    "Richard E. Borcherds" <reb@Math.Berkeley.EDU>,    bug-octave@bevo.che.wisc.edu
Date: Wed, 29 Jan 2003 21:42:01 -0600

On 23-Jan-2003, Mirek Kwasniak <mirek at zind dot ikem dot pwr dot wroc dot pl> wrote:

| On Wed, Jan 22, 2003 at 02:15:30PM -0600, John W. Eaton wrote:
| > BTW, Matlab also seems to behave this way, so any fix is likely to
| > break compatibility.
| 
| Yes we have compatibility, in fuctions rem, mod remainder can be greater
| then divisor :)
| 
| In a message:
|   http://groups.google.pl/groups?selm=eeb79a1.-1%40WebX.raydaftYaTP
| 
|  In MATLAB version 6.1 and 6.5,
| 
| 
|  >> rem(3.0782817340933185e+099,1e7)
|  ans =
|      4.856672230564323e+083
|  >> mod(3.0782817340933185e+099,1e7)
|  ans =
|      4.856672230564323e+083
| 
| 
| $ octave2.1
| GNU Octave, version 2.1.43 (i386-pc-linux-gnu).
| octave2.1:1> rem(3.0782817340933185e+099,1e7)
| ans =  4.8567e+83

Rather than try to "fix" this, I've introduced yet another function,
fmod, which simply calls the C library funciton fmod.  FWIW, with that
function I get the following result for your crazy numbers:

  octave:1> fmod (3.0782817340933185e+099, 1e7)
  ans = 7011968


jwe



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