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D.15.2.19 pdivisorplus

Procedure from library divisors.lib (see divisors_lib).

Usage:
pdivisorplus(A ,B); A + B; A = pdivisor, B = pdivisor.

Assume:
A and B are polyhedral divisors on X.

Return:
a pdivisor on X

Theory:
The procedure will add the polyhedral formal sums by doing Minkowski sums.

Example:
 
LIB "divisors.lib";
LIB("polymake.so");
==> Welcome to polymake
==> Copyright (c) 1997-2012
==> 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 A = makeDivisor(ideal(x,z),ideal(1));
divisor B = makeDivisor(ideal(x,y),ideal(1));
intmat M[4][4]= 1,4,0,0,
1,0,3,0,
0,0,0,2,
1,1,1,1;
polytope PP = polytopeViaPoints(M);
pdivisor pD = makePDivisor(list(list(PP,A),list(PP,B)));
pdivisorplus(pD,pD);
==> polymake: used package cddlib
==>   Implementation of the double description method of Motzkin et al.
==>   Copyright by Komei Fukuda.
==>   http://www.ifor.math.ethz.ch/~fukuda/cdd_home/cdd.html
==> 
==> tail=<cone>
==> summands=<list>

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