RosettaCodeData/Task/Time-a-function/Haskell/time-a-function.hs

import System.CPUTime (getCPUTime)

-- We assume the function we are timing is an IO monad computation
timeIt :: (Fractional c) => (a -> IO b) -> a -> IO c
timeIt action arg = do
  startTime <- getCPUTime
  action arg
  finishTime <- getCPUTime
  return $ fromIntegral (finishTime - startTime) / 1000000000000

-- Version for use with evaluating regular non-monadic functions
timeIt_ :: (Fractional c) => (a -> b) -> a -> IO c
timeIt_ f = timeIt ((`seq` return ()) . f)