```
function b=ucp(c)
% UCP(C) tests if the polynomial C is a Unit-Circle-Polynomial.
% It tests if all roots lie inside the unit circle like
% B=ucp(C) does the same as
% B=all(abs(roots(C))<1) but much faster.
% The Algorithm is based on the Jury-Scheme.
% C are the elements of the Polynomial
% C(1)*X^N + ... + C(N)*X + C(N+1).
%
% REFERENCES:
% O. Foellinger "Lineare Abtastsysteme", Oldenburg Verlag, Muenchen, 1986.
% F. Gausch "Systemtechnik", Textbook, University of Technology Graz, 1993.
% This library is free software; you can redistribute it and/or
% modify it under the terms of the GNU Library General Public
% License as published by the Free Software Foundation; either
% Version 2 of the License, or (at your option) any later version.
%
% This library 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
% Library General Public License for more details.
%
% You should have received a copy of the GNU Library General Public
% License along with this library; If not, see <http://www.gnu.org/licenses/>.
% Version 2.62
% 07.04.1999
% Copyright (C) 1996-1999 by Alois Schloegl <a.schloegl@ieee.org>
%
[lr,lc] = size(c);
% JURY-Scheme
b=ones(lr,1);
lambda=zeros(lr,1);
while (lc > 1),
lambda = c(:,lc)./c(:,1);
% disp([lc,size(lambda), sum(b),toc]);
% ratio must be less then 1
b = b & (abs(lambda) < 1);
% and reduced polynomial must be a UCP, too.
c(:,1:lc-1) = c(:,1:lc-1) - lambda(:,ones(1,lc-1)).*c(:,lc:-1:2);
lc = lc-1;
end;
```

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