\begin{code}
data UniqFM ele
= EmptyUFM
- | LeafUFM FastInt ele
- | NodeUFM FastInt -- the switching
- FastInt -- the delta
+ | LeafUFM !FastInt ele
+ | NodeUFM !FastInt -- the switching
+ !FastInt -- the delta
(UniqFM ele)
(UniqFM ele)
-- INVARIANT: the children of a NodeUFM are never EmptyUFMs