Singular Manual: pdivisorplus

| #### D.15.5.19 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 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 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 ppl
    ==>   The Parma Polyhedra Library (PPL): A C++ library for convex polyhedra
    ==>   and other numerical abstractions.
    ==>   http://www.cs.unipr.it/ppl/
    ==>
    ==> polymake: used package cdd
    ==>   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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