5.1.65 kernel

Syntax:

kernel ( ring_name, map_name )
preimage ( ring_name, ideal_expression )

Type:

ideal

Purpose:

returns the kernel of a given map.
The second argument has to be a map from the basering to the given ring (or an ideal defining such a map).

Example:

ring r1=32003,(x,y,z,w),lp; ring r=32003,(x,y,z),dp; ideal i=x,y,z; map f=r1,i; setring r1; // the kernel of f kernel(r,f); ==> _[1]=w