data NestedList a   =   Atom a | List [NestedList a]
nl = List [Atom 1, Atom 2, List [Atom 3, Atom 4, Atom 5], Atom 6, Atom 7]

data RTree a = RNode a [RTree a] deriving Show

getVal (RNode x _) = x

compute a b (Atom x) = RNode (b x) []
compute a b (List l) = RNode (a $ map getVal computed) $ computed
    where
        computed = map (compute a b) l

-- compute sum id nl

minmax f (x:xs) = foldr f x xs

params nl = (
            getVal $ compute (minmax min) id nl,
            getVal $ compute (minmax max) id nl,
            getVal $ compute ((+1) . (minmax max)) (const 0) nl)

t1 (a, _, _) = a
t2 (_, a, _) = a
t3 (_, _, a) = a

params2 :: (Num c, Ord t, Ord c) => NestedList t -> (t, t, c)
params2 = getVal . compute  
        (\results -> (
            minmax min $ map t1 results,
            minmax max $ map t2 results,
            (minmax max $ map t3 results) + 1
        ))
        (\x -> (x, x, 0))