import System.Directory (getDirectoryContents, doesDirectoryExist) data Tree a = Directory a [Tree a] | File a deriving (Show) makeTheTree :: FilePath -> IO (Tree FilePath) makeTheTree path = do isDirecotry <- doesDirectoryExist path if not isDirecotry then return $ File path else do content <- getDirectoryContents path tree <- mapM makeTheTree (processFiles content) return $ Directory path tree where processFiles :: [FilePath] -> [FilePath] processFiles files = map ((path ++) . ("/" ++)) $ discardDots files discardDots :: [FilePath] -> [FilePath] discardDots = filter (\file -> file /= "." && file /= "..") traverseBF :: Tree a -> [a] traverseBF tree = tbf [tree] where tbf [] = [] tbf xs = concatMap files xs ++ tbf (concatMap directories xs) files :: Tree a -> [a] files (File a) = [a] files (Directory _ _) = [] directories :: Tree a -> [Tree a] directories (File _) = [] directories (Directory _ ys) = ys main = (traverseBF <$> makeTheTree "/usr/local") >>= mapM_ (print . length . filter (=='/'))