z_axis wrote:

betterStdGen :: IO StdGen betterStdGen = alloca $ \p -> do h <- openBinaryFile "/dev/urandom" ReadMode hGetBuf h p $ sizeOf (undefined :: Int) hClose h mkStdGen <$> peek p

picoSec :: IO Integer picoSec = do t <- ctPicosec `liftM` (getClockTime >>= toCalendarTime) return t

The pseudo-code is :

if doesFileExist "/dev/urandom" then myGen = betterStdGen else myGen = (mkStdGen . fromTnteger) <$> picoSec

How to write these pseudo-code elegantly ?

I would do this: {-# LANGUAGE ScopedTypeVariables #-} readFrom :: forall a. Storable a => Handle -> IO a readFrom h = alloca $ \ptr -> hGetBuf h ptr (sizeOf (undefined :: a)) >> peek ptr newStdGen' :: IO StdGen newStdGen' = do mh <- try $ openBinaryFile "/dev/urandom" ReadMode case mh of Left err -> ctPicosec <$> (getClockTime >>= toCalendarTime) Right h -> mkStdGen <$> readFrom h `finally` hClose h Warning: Untested code, but it should work and have a safer file handling. Also note that the current implementation (base >= 4) does this already. You should probably try one of the more sophisticated PRNG libraries out there. Check out mersenne-random and mwc-random. If you want a pure generator, there is also mersenne-random-pure64 and some other libraries. Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/