def hum1_wei(x,y,n=24):
    t = y-1.0j*x
    cerf=1/sqrt(pi)*t/(0.5+t**2)
    """
    z = x+1j*y
    cerf = 1j*z/sqrt(pi)/(z**2-0.5)
    """
    mask = abs(x)+y<15.0
    if any(mask):
        w24 = weideman(x[mask],y[mask],n)
        place(cerf,mask,w24)
    return cerf.real,cerf.imag