truncate(s,n)
This function truncates the formal series s at the precision n.
i1 : R=ZZ[x,y] o1 = R o1 : PolynomialRing
i2 : s = series(x^7+x^2+x+y,7) 7 2 o2 = FormalSeries{x + x + x + y, 7} o2 : FormalSeries
i3 : truncate(s,4) 2 o3 = FormalSeries{x + x + y, 4} o3 : FormalSeries