lstar( x, u , option )

function sys = lstar( x, u , option )

% This function must be created by the user to define
% the performance weighting function L*()

if  option == 'value' 

% Return the value of L*(x,u,t)

    sys =  x(1)^2+ x(2)^2+ 0.1*u(1)^2;

elseif  option == 'gradz'  

% Return the gradient of L*(x,u,t) with respect to x

     sys  = zeros( 2,1 );

     sys(1) = 2*x(1);
     sys(2) = 2*x(2);

elseif  option == 'gradv'  

% Return the gradient of L*(x,u,t) with respect to u

          sys  = zeros( 1,1 );

          sys(1) = 2*0.1*u(1);
     


else sys = [];


end;

return;