This is a mess, in part because there should be more constants
throughout. I know we typically do exp- instead of the x_ business in
this change, but I also had to use this in some function names, so I
figured until I can break that coupling I'd go with this. If it's too
unpleasant during review, let me know and I can probably clean it up
some more.
- no-check-commit due to new foo_bar naming - too hard to avoid right now :(