/usr/share/octave/packages/communications-1.1.1/minpol.m is in octave-communications-common 1.1.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 | ## 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} {} minpol (@var{v})
##
## Finds the minimum polynomial for elements of a Galois Field. For a
## vector @var{v} with @math{N} components, representing @math{N} values
## in a Galois Field GF(2^@var{m}), return the minimum polynomial in GF(2)
## representing thos values.
## @end deftypefn
function r = minpol (v)
if (nargin != 1)
error("usage: r = minpol(v)");
endif
if (!isgalois(v))
error("minpol: argument must be a galois variable");
endif
if (min (size (v)) > 1 || nargin != 1)
usage ("minpol (v), where v is a galois vector");
endif
n = length (v);
m = v.m;
prim_poly = v.prim_poly;
r = zeros(n,m+1);
## Find cosets of GF(2^m) and convert from cell array to matrix
cyclocoset = cosets(m, prim_poly);
cyclomat = zeros(max(size(cyclocoset)),m);
for j=1:max(size(cyclocoset))
cyclomat(j,1:length(cyclocoset{j})) = cyclocoset{j};
end
for j =1:n
if (v(j) == 0)
## Special case
r(j,m-1) = 1;
else
## Find the coset within which the current element falls
[rc, ignored] = find(cyclomat == v(j));
rv = cyclomat(rc,:);
## Create the minimum polynomial from its roots
ptmp = gf([1,rv(1)], m, prim_poly);
for i=2:length(rv)
ptmp = conv(ptmp, [1,rv(i)]);
end
## Need to left-shift polynomial to divide by x while can
i = 0;
while (!ptmp(m+1-i))
i = i + 1;
end
ptmp = [zeros(1,i), ptmp(1:m+1-i)];
r(j,:) = ptmp;
endif
end
## Ok, now put the return value into GF(2)
r = gf(r,1);
endfunction
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