Plus, I don't think you have any unit tests of this feature (evan for easy functions).  Do we need this feature?  I'd be ok with just requiring xmin,xmax be supplied when giving a function.  Otherwise, I think we need some unit tests of this, at least for single modal distributions. And (either way) it would be worth adding unit tests with the function being a LookupTable to make sure xmin,xmax are correctly inferred from that.