truncate(ZZ,WittPolynomialRing) -- Crop Witt ring to the ring of Witt vectors of a given length

• Function: truncate

• Usage:

  V=truncate(n,W)

• Inputs:
  • n, an integer,
  • W, an instance of the type WittPolynomialRing,
• Outputs:
  • V, an instance of the type WittPolynomialRing,

i1 : S=ZZ/3[x,y]

o1 = S

o1 : PolynomialRing

i2 : W=witt(3,S)

o2 = Witt (S)
         3

o2 : WittPolynomialRing

i3 : truncate(2,W)

o3 = WittRingMap Witt (S) <-- Witt (S)
                     2            3

o3 : WittRingMap