System.Time.Extra

Extra functions for working with times. Unlike the other modules in this package, there is no corresponding System.Time module. This module enhances the functionality from Data.Time.Clock, but in quite different ways.

Throughout, time is measured in Seconds, which is a type alias for Double.

Documentation

type Seconds = Double

A type alias for seconds, which are stored as Double.

sleep :: Seconds -> IO ()

Sleep for a number of seconds.

fmap (round . fst) (duration $ sleep 1) == return 1

timeout :: Seconds -> IO a -> IO (Maybe a)

A version of timeout that takes Seconds and never overflows the bounds of an Int. In addition, the bug that negative timeouts run for ever has been fixed.

timeout (-3) (print 1) == return Nothing
timeout 0.1  (print 1) == fmap Just (print 1)
timeout 0.1  (sleep 2 >> print 1) == return Nothing
do (t, _) <- duration $ timeout 0.1 $ sleep 1000; return $ t < 1

subtractTime :: UTCTime -> UTCTime -> Seconds

Calculate the difference between two times in seconds. Usually the first time will be the end of an event, and the second time will be the beginning.

\a b -> a > b ==> subtractTime a b > 0

showDuration :: Seconds -> String

Show a number of seconds, typically a duration, in a suitable manner with responable precision for a human.

showDuration 3.435   == "3.44s"
showDuration 623.8   == "10m24s"
showDuration 62003.8 == "17h13m"
showDuration 1e8     == "27777h47m"

offsetTime :: IO (IO Seconds)

Call once to start, then call repeatedly to get the elapsed time since the first call. Values will usually increase, unless the system clock is updated (if you need the guarantee, see offsetTimeIncrease).

offsetTimeIncrease :: IO (IO Seconds)

Like offsetTime, but results will never decrease (though they may stay the same).

do f <- offsetTimeIncrease; xs <- replicateM 10 f; return $ xs == sort xs

duration :: IO a -> IO (Seconds, a)

Record how long a computation takes in Seconds.