data NLT a b = Node a (NLT a b) (NLT a b) | Leaf b

fold f g (Node a l r) = f a (fold f g l) (fold f g r)
fold f g (Leaf b) = g b

nls (Leaf b) = ([],[b])
nls (Node a l r) = (a:las++ras, lbs++rbs)
                   where (las,lbs) = nls l
                         (ras,rbs) = nls r

nl' = fold (\a (la,lb) (ra,rb) -> (a:la++ra, lb++rb)) (\b->([],[b]))

samp = Node 'a' (Node 'b' (Leaf 5) (Leaf 7))
                (Node 'c' (Leaf 8) (Node 'd' (Leaf 9) (Leaf 10)))



data BT a = Branch a (BT a) (BT a) | Tip

foldb b t (Branch x l r) = b x (foldb b t l) (foldb b t r)
foldb b t  Tip = t

inord = foldb (\x l r->l++x:r) []


t = Branch 3 (Branch 1 Tip (Branch 2 Tip Tip))
             (Branch 5 (Branch 4 Tip Tip)
                       (Branch 7 Tip (Branch 9 Tip Tip)) )

----------

ins (x,i) Tip = Branch (x,[i]) Tip Tip
ins (x,i) (Branch (y,is) l r) | x==y = Branch (y,i:is) l r
                              | x<y  = Branch (y,is) (ins (x,i) l) r
                              | x>y  = Branch (y,is) l (ins (x,i) r)

conc t = inord (foldr ins Tip (zip (words t) [1..]))

----------


text = "this a text with some words in it and some of the words appear twice \
		\and we are going to use only letters since it is hard to handle \
		\things like commas so this text of ours will run to many words \
		\and many of those words will be used twice such as words text in is it \
		\and so on"

fmt :: Show a => [(String,[a])] -> IO()
fmt = putStrLn . concatMap line
      where line (word, ints) = concat ["\n", word, "\t", comma (map show ints)]
            comma = foldr1 (\i str -> i ++ ", " ++ str)