

function out = qcon(f,corners,n)
   if nargin < 3
        n = 50;
    end
   x = linspace( corners(1), corners(2), n+1);
   y = linspace( corners(3), corners(4), n+1);
   [X,Y] = meshgrid(x,y);
   Z = feval(f,X,Y);
   contour(X,Y,Z)