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5.1.68 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
See alg_kernel; hom_kernel; ideal; map; modulo; preimage; ring.