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D.5.4.1 makeDivisor

Procedure from library divisors.lib (see divisors_lib).

Usage:
makeDivisor(I ,J); I = ideal, J = ideal.

Assume:
I and J are ideals in a qring Q of a smooth irreducible variety X such that any ideal in Q satisfies the S2 condition.

Return:
a divisor on X

Theory:
The procedure will eliminate all components which are not of codimension 1. The S2 condition requires that every proper nonzero principal ideal has pure codimension 1.

Example:
 
LIB "divisors.lib";
==> Welcome to polymake version
==> Copyright (c) 1997-2015
==> Ewgenij Gawrilow, Michael Joswig (TU Darmstadt)
==> http://www.polymake.org
ring r=31991,(x,y,z),dp;
ideal I = y^2*z - x*(x-z)*(x+3*z);
qring Q = std(I);
divisor P = makeDivisor(ideal(x,z),ideal(1));