gistfile1.hs

-- Rabhi and Lapalme, Algorithms: A Functional Programming Approach, pg 80

data BinTree a = Empty | NodeBT a (BinTree a) (BinTree a) deriving Show

ex = NodeBT 42 (NodeBT 4 Empty Empty) (NodeBT 2 Empty Empty)

comp'' x Empty = (Empty, 0)
comp'' x (NodeBT v lf rt) = ( NodeBT (fromIntegral v / fromIntegral x) p1 p2
                            , v + s1 + s2 )
 where
  (p1,s1) = comp'' x lf
  (p2,s2) = comp'' x rt

comp' t = t'
 where (t',x) = comp'' x t
  -- I have a hard time with the 'x' here (in t',x)
  -- is that tying the knot?