back out change wrt 0 as that was not syntactically valid.  Change disint to use Msum() instead, as that is where it was coming from.  Tests still pass.
back out change wrt 0 as that was not syntactically valid.  Change disint to use Msum() instead, as that is where it was coming from.  Tests still pass.

zachsully/hakaru,zaxtax/hakaru,zaxtax/hakaru,zachsully/hakaru