FormalGroupPoint - FormalGroupPoint -- difference of points of a formal group

i1 : ZZ[x,y]

o1 = ZZ[x..y]

o1 : PolynomialRing

i2 : f = FGL(series(x+y+x*y,10))

o2 = FormalGroupLaw{x*y + x + y, 10}

o2 : FormalGroupLaw

i3 : ZZ[u]

o3 = ZZ[u]

o3 : PolynomialRing

i4 : s = formalGroupPoint(f,series(u^2+u,5))

                                                                     2
o4 = FormalGroupPoint{FormalGroupLaw{x*y + x + y, 10}, FormalSeries{u  + u, 5}}

o4 : FormalGroupPoint

i5 : t = formalGroupPoint(f,series(u^3,5))

                                                                     3
o5 = FormalGroupPoint{FormalGroupLaw{x*y + x + y, 10}, FormalSeries{u , 5}}

o5 : FormalGroupPoint

i6 : s-t

                                                                       5    4    3    2
o6 = FormalGroupPoint{FormalGroupLaw{x*y + x + y, 10}, FormalSeries{- u  - u  - u  + u  + u, 5}}

o6 : FormalGroupPoint