# Differentiation of a power series.

I wonder whether it is too hard to implement the derivative function for multivariate Power Series Ring. Since it is already implemented for one variable, is it not possible to implement it for multivariable, by treating the ring in one var over the ring in other vars.

e.g.

QQ[[x,y,z]] = QQ[[x,y]][z]]

Thanks and regards

--VInay