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D.15.17.2 SGNF

Procedure from library sagbigrob.lib (see sagbigrob_lib).

Usage:
SGNF(f,I,A); f polynomial, I ideal of subalgebra
A, A ideal (which is a finite Sagbi bases).

Return:
a polynomial h: the normalform of f wrt. I in A

Example:
 
LIB "sagbigrob.lib";
ring r=0,(x,y),Dp;
ideal A=x2,xy;
ideal I=x3y+x2,x4+x2y2,-x3y3-x2y2;
poly f=x6y6+x2;
poly g=x12+x6y6-x8+x5y;
SGNF(f,I,A);
==> x2y2+x2
SGNF(g,I,A);
==> 0