Using the supplied interactWith function, write another function that writes the first word of each line to another file.

writeFirstWords.hs

interactWith :: (String -> String) -> FilePath -> FilePath -> IO ()
interactWith f inputFile outputFile = do
  input <- readFile inputFile
  writeFile outputFile (f input)

writeFirstWords inputFile outputFile = interactWith firstWords inputFile outputFile where
  firstWord "" = ""
  firstWord line = head $ words line
  firstWords file = unlines $ map firstWord $ lines file