mbixby

-- parseExpr :: something -> Either ParseError Expression 
convert :: String -> Either String String
convert input = case parseExpr input of
              Left err -> Left $ show err
              Right x  -> Right $ show x

-- Want:
convert = magicfunction show $ parseExpr

mbixby

data Tree a = Leaf a | Node a [Tree a]

scanDir :: String -> IO (Tree String)
scanDir path = do
  contents <- getDirectoryContents path `catch` const (return [])
  let files = sort . filter (`notElem` [".", ".."]) $ contents
  let pathsAndFiles = zip (repeat path) files
  tree <- forM pathsAndFiles $ \(path, file) -> do
    isDirectory <- doesDirectoryExist path
    if isDirectory