Home Online Manual
Top
Back: semidiv
Forward: cantorred
FastBack:
FastForward:
Up: hyperel_lib
Top: Singular Manual
Contents: Table of Contents
Index: Index
About: About this document

D.12.4.9 cantoradd

Procedure from library hyperel.lib (see hyperel_lib).

Usage:
cantoradd(D,Q,h,f);

Return:
list P

Note:
Cantor's Algorithm - composition
important: D and Q have to be semireduced!
Computes semireduced divisor div(P[1],P[2])= div(D[1],D[2]) + div(Q[1],Q[2]) The divisors are defined over the basering.
Curve C: y^2+h(x)y=f(x) is defined over the basering.

Example:
 
LIB "hyperel.lib";
ring R=7,x,dp;
// hyperelliptic curve y^2 + h*y = f
poly h=x;
poly f=x5+5x4+6x2+x+3;
// two divisors in rational representation
list D=x2-1,2x-1;
list Q=x2-3x+2,-3x+1;
cantoradd(D,Q,h,f);
==> [1]:
==>    x2-x-2
==> [2]:
==>    -3x+1