Description
L must be a list of weights, exactly one for each ray of the fan. Then the Cartier index is the smallest strictly positive natural number $N$ such that $N$ times the Weil divisor is Cartier. If the Weil divisor defined by these weights is not
QQ-Cartier, then $N$ would be infinity. In this case
cartierIndex returns an error. Otherwise it returns $N$.
i1 : F = fan posHull matrix {{1,5},{5,1}}
o1 = F
o1 : Fan
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i2 : L = {2,2}
o2 = {2, 2}
o2 : List
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i3 : cartierIndex(L,F)
o3 = 3
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If we change the Weil divisor we get a different Cartier index:
i4 : L = {3,3}
o4 = {3, 3}
o4 : List
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i5 : cartierIndex(L,F)
o5 = 2
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