/usr/share/octave/packages/communications-1.1.1/cosets.m is in octave-communications-common 1.1.1-1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 | ## 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} {} cosets (@var{m}, @var{prim})
##
## Finds the elements of GF(2^@var{m}) with primitive polynomial
## @var{prim}, that share the same minimum polynomial. Returns a
## cell array of the paratitioning of GF(2^@var{m}).
## @end deftypefn
function c = cosets(m, prim)
if (nargin == 1)
prim = 0; ## This flags to use default primitive
elseif (nargin != 2)
error ("usage: c = cosets (m [, prim])");
endif
n = 2^m-1;
found = zeros(1,n);
c{1} = gf(1,m,prim);
found(1) = 1;
nc = 2;
f = log(gf(1:n,m,prim));
while ((!all(found)))
t = find(!found);
idx = f(t(find(f(t) == min(f(t).x)))).x;
set = idx;
r = rem(idx*2,n);
while (r > idx)
set =[set,r];
r = rem(r*2,n);
end
c{nc} = gf(sort(exp(gf(set,m,prim)).x),m,prim);
found(c{nc}.x) = ones(1,length(c{nc}));
nc = nc + 1;
end
endfunction
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