|
 |
 |
 |
 |
 |
 |
 |
 |
 |
D.5.4.10 effective
Procedure from librarydivisors.lib (see divisors_lib).
- Usage:
- effective(A); A = divisor.
- Assume:
- A is a divisor on X which is linearly equivalent to an effective divisor.
- Return:
- divisor on X.
- Theory:
- We compute an effective divisor linearly equivalent to A.
LIB "divisors.lib"; 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)); divisor D = divisorplus(multdivisor(2,B),negativedivisor(A)); effective(D); ==> (z,x) - (1) ==> |