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D.2.11.14 preimageLoc

Procedure from library ring.lib (see ring_lib).

Usage:
preimageLoc ( ring_name, map_name, ideal_name );
all input parameters of type string

Return:
ideal

Purpose:
compute the preimage of an ideal under a given map for non-global orderings.
The 2nd argument has to be the name of a map from the basering to the given ring (or the name of an ideal defining such a map), and the ideal has to be an ideal in the given ring.

Example:
 
LIB "ring.lib";
ring S =0,(x,y,z),dp;
ring R0=0,(x,y,z),ds;
qring R=std(x+x2);
map psi=S,x,y,z;
ideal null;
setring S;
ideal nu=preimageLoc("R","psi","null");
nu;
==> nu[1]=x
See also: preimage.