projectiveProduct -- Makes a product of projective spaces and a system of parameters

Synopsis

Usage:

(S, params) = projectiveProduct(A,dimList)
Inputs:
- A, a ring,
- dimList, a list, A the desired base ring. dimList a list of dimensions {d1..dn}
Outputs:
- S, a ring,
- params, a matrix, S is the iterated tower ring A[x_(0,0)..x_(0,d1)]..[..x_(n,dn)] representing the product P_A^{d1} x ..x P_A^{dn}, where the products are relative to A, and params is a system of multilinear forms in S. They are sparse if M is not present, or determined by M if it is.