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5.1.106 preimage

Syntax:
preimage ( map )
preimage ( ring_name, map_name, ideal_name )
preimage ( ring_name, ideal_expression, ideal_name )
Type:
ring
ideal
Purpose:
returns the source ring of a map (in the first case) or returns the preimage of an ideal under 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), and the ideal has to be an ideal in the given ring.
Note:
As preimage is handling ideals (not polynomials), the result of a preimage calculation of a principal ideal is (the closure of) the preimage of the ideal, not that of the polynomial.
Example:
 
See ideal; kernel; map; ring.

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            User manual for Singular version 3-1-6, Dec 2012, generated by texi2html.