# Singular

#### D.15.11.19 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"; ==> Welcome to polymake version ==> Copyright (c) 1997-2015 ==> Ewgenij Gawrilow, Michael Joswig (TU Darmstadt) ==> http://www.polymake.org LIB("polymake.so"); 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/ ==> ==> tail= ==> summands= ```