Re: Double problem in Matlab's magic.m

[Quentin Spencer]

Henry F. Mollet wrote:

> Presumably, 'mod' is modulus function but it's not in the GNU Octave
> Function Index (Hard Copy for Octave version 2.0.13) and  help cannot find
> it in my copy either (GNU Octave, version 2.1.35 (powerpc-apple-darwin6.2).
> However, the Octave program 'magic' by PK is using it?
> Henry
>  
The mod function was in octave-forge, but has been moved into the main 
octave distribution sometime after 2.1.35. Here's the current CVS 
version (minus some commented stuff at the end):


## Copyright (C) 1999, 2000 Paul Kienzle
##
## This file is part of Octave.
##
## Octave is free software; you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2, or (at your option)
## any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
## General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING.  If not, write to the Free
## Software Foundation, 59 Temple Place - Suite 330, Boston, MA
## 02111-1307, USA.

## -*- texinfo -*-
## @deftypefn {Mapping Function} {} mod (@var{x}, @var{y})
## Compute modulo function, using
##
## @example
## x - y .* floor (x ./ y)
## @end example
##
## Note that this handles negative numbers correctly:
## @code{mod (-1, 3)} is 2, not -1 as @code{rem (-1, 3)} returns.
## Also, @code{mod (@var{x}, 0)} returns @var{x}.
##
## An error message is printed if the dimensions of the arguments do not
## agree, or if either of the arguments is complex.
## @end deftypefn
## @seealso{rem, round}

## Author: Paul Kienzle <address@hidden>
## Modified by: Teemu Ikonen <address@hidden>
## Adapted by: jwe

function r = mod (x, y)

 if (nargin != 2)
   usage ("r = mod (x, y)");
 endif

 if (any (size (x) != size (y)) && ! (isscalar (x) || isscalar (y)))
   error ("mod: argument sizes must agree");
 endif

 ## Matlab allows complex arguments, but as far as I can tell, that's a
 ## bunch of hooey.

 if (isreal (x) && isreal (y))
   nz = y != 0.0;
   if (all (nz(:)))
     ## No elements of y are zero.
     r = x - y .* floor (x ./ y);
   elseif (isscalar (y))
     ## y must be zero.
     r = x;
   else
     ## Some elements of y are zero.
     if (isscalar (x))
       r = x * ones (size (y));
     else
       r = x;
       x = x(nz);
     endif
     y = y(nz);
     r(nz) = x - y .* floor (x ./ y);
   endif
 else
   error ("mod: complex arguments are not allowed");
 endif

endfunction




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