Sums its arguments and also prints them in order

Sum.hs

#!/usr/bin/env runghc
import System.Environment
import Control.Monad.Writer
import Control.Applicative

mySum :: (Num a, Show a) => [a] -> Writer [String] a
mySum []     = return 0
mySum (x:xs) = censor ((show x):) ((x+) <$> mySum xs)

main = do
  args <- getArgs
  let (sum, logs) = runWriter $ mySum $ map read args
  print logs
  print $ "Sum: " ++ show sum

SumIO.hs

#!/usr/bin/env runghc
import System.Environment
import Control.Monad.Writer
import Control.Applicative
import System.Time

type WriterIO a = WriterT [String] IO a

mySum :: (Num a, Show a) => [a] -> WriterIO a
mySum []     = return 0
mySum (x:xs) = do
  logLine <- liftIO $ myLog x
  censor (logLine:) ((x+) <$> mySum xs)
  where
    myLog :: (Num a, Show a) => a -> IO String
    myLog num = do
      time <- getClockTime
      return $ (show time) ++ " " ++ show num

main = do
  args <- getArgs
  (sum, logs) <- runWriterT $ mySum $ map read args
  print logs
  print $ "Sum: " ++ show sum

$ ./tmp 1 2 3
["1","2","3"]
"Sum: 6"