Exponential of constant polynomial

[fredrik-johansson]

A user reported this:

julia> F=Nemo.AcbField(20)
Complex Field with 20 bits of precision and error bounds

julia> S1, x = PowerSeriesRing(F, 3, "x")
(Univariate power series ring over complex Field with 20 bits of precision and error bounds, x + O(x^4))

julia> exp(1+x)
[2.71828 +/- 4.63e-6] + [2.71828 +/- 4.63e-6]*x + [1.35914 +/- 2.32e-6]*x^2 + O(x^3)

julia> P,a=AbstractAlgebra.PolynomialRing(F,["a"])
(Multivariate polynomial ring in 1 variable over complex Field with 20 bits of precision and error bounds, AbstractAlgebra.Generic.MPoly{acb}[a])

julia> S2, y = PowerSeriesRing(P, 3, "y")
(Univariate power series ring over multivariate polynomial ring, y + O(y^4))

julia> exp(1+y)
ERROR: Exponential of nonzero element

One could define exp() and similar functions for constant polynomials to act on the constant.