Home Online Manual
Top
Back: formaldivisorplus
Forward: multformaldivisor
FastBack:
FastForward:
Up: divisors_lib
Top: Singular Manual
Contents: Table of Contents
Index: Index
About: About this document

D.5.4.14 negativeformaldivisor

Procedure from library divisors.lib (see divisors_lib).

Usage:
negativeformaldivisor(A); A = formaldivisor.

Assume:
A is a formaldivisor on X.

Return:
a formal divisor on X

Theory:
The procedure will change the signs of the coefficients.

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 A = makeDivisor(ideal(x,z),ideal(1));
divisor B = makeDivisor(ideal(x,y),ideal(1));
formaldivisor fE= makeFormalDivisor(list(list(-5,A),list(2,B)));
negativeformaldivisor(fE);
==> 5*( (z,x) - (1) )
==> -2*( (y,x) - (1) )
==>