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

Function: isEffectiveExpression
Usage:

isEffectiveExpression(D)
Inputs:
- D, an instance of the type DivisorClassRepresentativeM0nbar,
Outputs:
- a Boolean value,

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

Ways to use this method:

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

The source of this document is in M0nbar.m2:1938:0.