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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
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