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D.15.5.14 negativeformaldivisor
Procedure from librarydivisors.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.
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)); formaldivisor fE= makeFormalDivisor(list(list(-5,A),list(2,B))); negativeformaldivisor(fE); |