getFileNames :: String -> (String, String)
getFileNames str
   | isSuffixOf ".hs" str = (str, take (length str - 3) str)
   | otherwise = error $ "Not a Haskell filename: " ++ str
getFileNames :: String -> (String, String)
getFileNames str
   | isSuffixOf ".hs" str = (str, take (length str - 3) str)
   | otherwise = error $ "Not a Haskell filename: " ++ str
getFileNames str
   | isSuffixOf ".hs" str = (str, take (length str - 3) str)
   | otherwise = error $ "Not a Haskell filename: " ++ str