Dear Ryan, all, To quote the documentation of System.Random: "The Show and Read instances of StdGen provide a primitive way to save the state of a random number generator." Primitive it is indeed. Currently the only way to serialize (using cereal or binary) a StdGen is to convert it to a String and then serialize this String. This takes up many more bytes than are actually needed. I would like to propose a more efficient way of serializing the state of the random number generator by providing the following two functions: getStdGenState :: StdGen -> (Int32, Int32) getStdGenState (StdGen s1 s2) = (s1, s2) stdGenFromState :: (Int32, Int32) -> StdGen stdGenFromState (s1, s2) = StdGen s1 s2 Of course this satisfies: (stdGenFromState . getStdGenState) g == g Alternatively, instead of using (Int32, Int32) we can use an Int64: getStdGenState :: StdGen -> Int64 getStdGenState (StdGen s1 s2) = fromIntegral s1 `unsafeShiftL` 32 .|. fromIntegral s2 #if !MIN_VERSION_base(4,5,0) where unsafeShiftL = shiftL #endif stdGenFromState :: Int64 -> StdGen stdGenFromState s = StdGen (fromIntegral (s `unsafeShiftR` 32)) (fromIntegral s) #if !MIN_VERSION_base(4,5,0) where unsafeShiftR = shiftR #endif I don't really care which one we use but I think the latter is a bit easier to use. Oh, I don't really care about the names either. Regards, Bas