ln fails on create-standalone

[chrisvfritz]

When including ln in a model, this error results:

unknown primitive: org.nlogo.prim.etc._ln

This can be worked around by essentially re-implementing a natural log function to the accuracy you need with something like the Maclaurin series, but I think that's a bit tedious and would be completely beyond many people for whom ln is a black box.

[TheBizzle]

Duplicate of NetLogo/Tortoise#119.