There seems to be a problem with elevating z to the zeroth exponent.

julia> let z = Poly([0.0, 1]),
           z1 = z^3 + z^0;
           length(z1), z1[end]
       end
(5,0.0)

So, z1 has length 5, which does not seems correct. I would have expected a length 3 underlying array, corresponding to a degree 3 polynomial. Here I am trying to access the coefficient of greatest degree for the polynomial. Is there a degree function? A related problem is that 0*z^5 is of length 6 and thus the length does not give the degree.