isEffective(ToricDivisor) -- whether a torus-invariant Weil divisor is effective

• Function: isEffective

• Usage:

  isEffective D

• Inputs:
  • D, a toric divisor,
• Outputs:
  • a Boolean value, that is true if all the coefficients of the irreducible torus-invariant divisors are nonnegative

i1 : PP3 = toricProjectiveSpace 3;

i2 : K = toricDivisor PP3

o2 = - PP3  - PP3  - PP3  - PP3
          0      1      2      3

o2 : ToricDivisor on PP3

i3 : isEffective K

o3 = false

i4 : isEffective (-K)

o4 = true