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M0nbar :: isEffectiveExpression(DivisorClassRepresentativeM0nbar)

isEffectiveExpression(DivisorClassRepresentativeM0nbar) -- determines whether a divisor class expression is effective

Synopsis

Description

This function tests whether the coefficients in an object of type DivisorClassRepresentativeM0nbar are all nonnegative.

Warning: this function tests only the input representative of a divisor class. That is, it answers whether the input is an effective expression, not whether there exists an effective expression equivalent to the input.

i1 : L1= { {{3,1},-1}, {{1,4},1} };
i2 : D1=divisorClassRepresentativeM0nbar(6,L1)

o2 = DivisorClassRepresentativeM0nbar{DivisorExpression => HashTable{{1, 3} => -1}}
                                                                     {1, 4} => 1
                                      NumberOfMarkedPoints => 6

o2 : DivisorClassRepresentativeM0nbar
i3 : isEffectiveExpression(D1)

o3 = false
i4 : L2= { {{3,1},1}, {{1,4},1} };
i5 : D2=divisorClassRepresentativeM0nbar(6,L2)

o5 = DivisorClassRepresentativeM0nbar{DivisorExpression => HashTable{{1, 3} => 1}}
                                                                     {1, 4} => 1
                                      NumberOfMarkedPoints => 6

o5 : DivisorClassRepresentativeM0nbar
i6 : isEffectiveExpression(D2)

o6 = true