{-
risers :: Ord a => [a] -> [[a]]
risers []     = []
risers [x]    = [[x]]
risers (x:xs) = case risers xs of
                  (y:ys):yss | x <= y -> (x:y:ys):yss
                  yss                 -> [x]:yss
-}

risers :: Ord a => [a] -> [[a]]
risers []       = []
risers :: Ord a => [a] -> [[a]]
risers []       = []
risers []       = []