# UnivariatePolynomialCategoryFunctions2(R, PR, S, PS)¶

Mapping from polynomials over R to polynomials over S given a map from R to S assumed to send zero to zero.
map(f, p) takes a function f from R to S, and applies it to each (non-zero) coefficient of a polynomial p over R, getting a new polynomial over S. Note: since the map is not applied to zero elements, it may map zero to zero.