treeCont.hs

data Tree a = Leaf a | Branch (Tree a) (Tree a) deriving Show

t = Branch 
    (Branch 
     (Leaf 1) 
     (Leaf 2))
    (Branch
     (Leaf 3)
     (Branch 
      (Leaf 4)
      (Leaf 5)))

leafCount (Leaf _)     = 1
leafCount (Branch l r) = leafCount l + leafCount r

leafCount_cps (Leaf _)     k = k 1
leafCount_cps (Branch l r) k = leafCount_cps l $ \x ->
                               leafCount_cps r $ \y ->
                               k $ x + y
                               
main = do print $ leafCount t
          print $ leafCount_cps t (\x -> x)
          leafCount_cps t print