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## Copyright (C) 1996 John W. Eaton
##
## 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.
## usage: gcd (a, ...)
##
## [g [, v]] = gcd (a) returns the greatest common divisor g of the
## entries of the integer vector a, and an integer vector v such that
## g = v(1) * a(k) + ... + v(k) * a(k).
##
## [g [, v]] = gcd (a1, ..., ak) is the same with a = [a1, ..., ak].
## Author: KH <Kurt.Hornik@ci.tuwien.ac.at>
## Created: 16 September 1994
## Adapted-By: jwe
function [g, v] = gcd (a, ...)
if (nargin == 0)
usage ("[g, v] = gcd (a, ...)");
endif
if (nargin > 1)
va_start;
for k = 2:nargin;
a = [a, (va_arg ())];
endfor
endif
if (round (a) != a)
error ("gcd: all arguments must be integer");
endif
g = abs (a(1));
v = sign (a(1));
for k = 1:(length (a) - 1)
x = [g, 1, 0];
y = [(abs (a(k+1))), 0, 1];
while (y(1) > 0)
r = x - y * floor (x(1) / y(1));
x = y;
y = r;
endwhile
g = x(1);
v = [x(2) * v, x(3) * (sign (a(k+1)))];
endfor
endfunction
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