Singular

D.2.9.7 pnormalform

Usage:

pnormalform(f,N,W);
f: the polynomial to be reduced modulo N,W (in parameters and variables)
N: the null conditions ideal
W: the non-null conditions (set of irreducible polynomials, ideal)

Return:

a reduced polynomial g of f, whose coefficients are reduced modulo N and having no factor in W.

Note:

Should be called from ring @R. Ideals N and W must be polynomials in the parameters forming a red-specification (see definition) the papers).

LIB "redcgs.lib";
ring R=(0,a,b,c),(x,y),dp;
setglobalrings();
poly f=(b^2-1)*x^3*y+(c^2-1)*x*y^2+(c^2*b-b)*x+(a-bc)*y;
ideal N=(ab-c)*(a-b),(a-bc)*(a-b);
ideal W=a^2-b^2,bc;
def r=redspec(N,W);
pnormalform(f,r[1],r[2]);
==> xy2+(b)*x