--- /dev/null
+## Copyright (C) 2002 David Bateman
+##
+## This program 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 3 of the License, or (at your option) any later
+## version.
+##
+## This program 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
+## this program; if not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} conv (@var{a}, @var{b})
+## Convolve two Galois vectors.
+##
+## @code{y = conv (a, b)} returns a vector of length equal to
+## @code{length (a) + length (b) - 1}.
+## If @var{a} and @var{b} are polynomial coefficient vectors, @code{conv}
+## returns the coefficients of the product polynomial.
+## @end deftypefn
+## @seealso{deconv}
+
+function y = conv (a, b)
+
+ if (nargin != 2)
+ usage ("conv(a, b)");
+ endif
+
+ if (!isgalois (a) && !isgalois (b))
+ error("conv: at least one argument must be a galois variable");
+ elseif (!isgalois (a))
+ a = gf(a, b.m, b.prim_poly);
+ elseif (!isgalois (b))
+ b = gf(b, a.m, a.prim_poly);
+ elseif (a.m != b.m && a.prim_poly != b.prim_poly)
+ error("conv: both vectors must be in the same galois field");
+ endif
+
+ if (min(size(a)) > 1 || min(size(b)) > 1)
+ error("conv: both arguments must be vectors");
+ endif
+
+ la = length (a);
+ lb = length (b);
+
+ ly = la + lb - 1;
+
+ ## Ensure that both vectors are row vectors.
+ if (rows (a) > 1)
+ a = reshape (a, 1, la);
+ endif
+ if (rows (b) > 1)
+ b = reshape (b, 1, lb);
+ endif
+
+ ## Use the shortest vector as the coefficent vector to filter.
+ if (la < lb)
+ if (ly > lb)
+ ## Can't concatenate galois variables like this yet
+ ## x = [b, (zeros (1, ly - lb))];
+ x = gf([b, (zeros (1, ly - lb))], b.m, b.prim_poly);
+ else
+ x = b;
+ endif
+ y = filter (a, 1, x);
+ else
+ if(ly > la)
+ ## Can't concatenate galois variables like this yet
+ ## x = [a, (zeros (1, ly - la))];
+ x = gf([a, (zeros (1, ly - la))], a.m, a.prim_poly);
+ else
+ x = a;
+ endif
+ y = filter (b, 1, x);
+ endif
+
+endfunction