[Haskell-beginners] Printing the result of a function evaluation

Why oh why doesn't this work as I expect, and what is the simplest fix?  speedTest 4 = 44 time :: (Show t) => IO t -> IO t time a = do     start <- getCPUTime     v <- a     end   <- getCPUTime     let diff = (fromIntegral (end - start)) / (10^12)     print v -- WHY DOESNT THIS WORK?  ALWAYS PRINTS () ....     printf "Computation time: %0.3f sec\n" (diff :: Double)     return v main :: IO () main = do     args <- getArgs     time $ speedTest (read $ head args) `seq` return ()