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D.5.4.13 formaldivisorplus
Procedure from library divisors.lib (see divisors_lib).
- Usage:
- formaldivisorplus(A ,B); A + B; A = formaldivisor, B = formaldivisor.
- Assume:
- A and B are formal divisors on X.
- Return:
- a formal divisor on X
- Theory:
- The procedure will add the formal sums.
Example:
| | 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 C = makeDivisor(ideal(x-z,y),ideal(1));
formaldivisor fE= makeFormalDivisor(list(list(-5,A),list(2,B)));
formaldivisor fE2= makeFormalDivisor(list(list(-5,A),list(2,C)));
formaldivisorplus(fE,fE2);
==> [1]:
==> [1]:
==> -10
==> [2]:
==> (z,x) - (1)
==>
==> [2]:
==> [1]:
==> 2
==> [2]:
==> (y,x) - (1)
==>
==> [3]:
==> [1]:
==> 2
==> [2]:
==> (y,x-z) - (1)
==>
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