main = do 
     innm:outnm:_ <- getArgs
     lns <- lines `fmap` readFile innm
     writeFile outnm $ unlines $ f lns
main = do 
     innm:outnm:_ <- getArgs
     lns <- lines `fmap` readFile innm
     writeFile outnm $ unlines $ f lns
main = do 
     innm:outnm:_ <- getArgs
     lns <- lines `fmap` readFile innm
     writeFile outnm $ unlines $ f lns