|This article is about a function from ApCoCoA-2.|
This function returns a truncated SAGBI basis of a given standard-graded subalgebra.
SB.GetTruncSAGBI(ref S: TAGGED("$apcocoa/sagbi.Subalgebra"), d: INT): LIST of POLY
This function takes a subalgebra S generated by homogeneous polynomials as a reference, computes a d-truncated SAGBI basis, returns it and saves it into S if the function wasn't called previously. If the function was called previously on the same subalgebra with the same or a higher truncation degree d, then it just returns the truncated SAGBI basis of S.
@param S A subalgebra
@param d A positive integer
@return A d-truncated SAGBI basis of S
Use P ::= QQ[x,y,z]; S := SB.Subalgebra(P,[x^2 -z^2, x*y +z^2, y^2 -2*z^2]); PrintLn SB.GetTruncSAGBI(S,3); -- [y^2 -2*z^2, x*y +z^2, x^2 -z^2]