% quadf - scalar quadratic form
%
% quadf :: [Size], real -> [Size].
% quadf :: [Size] -> [Size].
%
% Scalar function: quadf(x,s) = -x^2/(2*s), s defaults to 1.
function y=quadf(x,s), if nargin<2, y=-(x.^2)/2; else y= -(x.^2)/(2*s); end
