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conv.m    86 lines (74 with data), 2.5 kB

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## 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.
## @seealso{deconv}
## @end deftypefn
function y = conv (a, b)
if (nargin != 2)
print_usage ();
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
%%Test input validation
%!error conv (gf (1, 2), gf (1, 3))
%!error conv (gf (eye (3), 3), gf (eye (3), 3))