import pylab as pl

def p_margin(H, type='d', Ts=1):

    // |h(e^(i*w*dt))|=1 <-- h(e^(i*w*dt))*h(e^(-i*w*dt))

    z=poly(0,varn(h.den));

    den = H.den

    sm=simp_mode();simp_mode(%f);hh=h*horner(h,1/z)-1;simp_mode(sm)

    //find the numerator roots

    z=roots(hh.num);

    z(abs(abs(z)-1)>eps)=[];// retain only roots with modulus equal to 1

    w=log(z)/(%i*dt);

    ws=real(w(abs(imag(w))<eps&real(w)>0)); //frequency points with unitary modulus

    if ws==[] then phm=%inf,fr=[],return,end

    f=horner(h,exp(%i*ws*dt));

  end

    return phm, fr

def g_margin(H, type='d', Ts=1):

    return gm, fr