%
% Optical Imaging and Spectroscopy
%
% David J. Brady
% Duke University
% www.opticalimaging.org
%
% function to find the quadratic residues modulo prime number p between 1
% and p-1. The function returns a list with value 1 for all indices which
% are quadratic residues modulo p and value 0 for indices which are not
% quadratic residues.
%
function qr=qres(p)
qr=zeros(1,p-1);
for i=1:(p-1)
    qr(mod(i^2,p))=1;
end