Something for rigid output.  Not looking correct though.
factor lambda in the return
BUG: return output, not just Z
BUG: Fix their typo on eq 18.

This gives a more sensible number for output.  Still need to check
What I think is correct for eq 18.  Not reasonable answer
"Generalze lininterp (again)"
Generalizing LinInterp
BUG: Fixing up tests to match Interp generalization.