function ps82(a)
if nargin<1, a=1; end
z=tf('z');
G=(1-a^2+a/z)/z;
sig=hsvd(G);
if a>1,
    Gr=(1-a^2)/(z+1/a);
    GAM=1;
elseif a<1,
    Gr=(1-a^2)/(z-a);
    GAM=a^2;
else
    Gr=0;
    GAM=1;
end
Gr1=tf(hankelmr(G,1))
er=max(hsvd(Gr-Gr1));
fprintf('GAMMA:    analytical %f,  numerical %f\n',GAM,sig(2))
fprintf('MISMATCH: %e\n',er)
fprintf('HinfErr:  analytical %f,  numerical %f\n',norm(G-Gr,Inf),norm(G-Gr1,Inf))