matrix(RingMap) -- the matrix associated to a ring map

Synopsis

Usage:
matrix f
Function: matrix
Inputs:
- f, a ring map
Outputs:
- the matrix associated to the ring map f, computed by applying f to the matrix of variables of its source ring
Optional inputs:
- Degree => ..., -- not really an option?
- DegreeMap => ..., -- not really an option

i1 : R = QQ[x,y]

o1 = R

o1 : PolynomialRing

i2 : S = QQ[s,t,u]

o2 = S

o2 : PolynomialRing

i3 : f = map(R,S,{x^2,x*y,y^2})

               2        2
o3 = map(R,S,{x , x*y, y })

o3 : RingMap R <--- S

i4 : matrix f

o4 = | x2 xy y2 |

             1       3
o4 : Matrix R  <--- R