Ticket #3575: random-seed.hs

import Control.Monad
import System.Random
import System.IO

print0or1 = do
  g <- newStdGen
  putStr . show . fst $ randomR (0, 1 :: Int) g

main = do
  -- These four lines read an initial seed from /dev/urandom.
  f <- openBinaryFile "/dev/urandom" ReadMode
  xs <- replicateM 4 $ hGetChar f
  let seed = sum $ zipWith (*) (iterate (* 256) 1) (map fromEnum xs)
  setStdGen $ mkStdGen seed

  replicateM_ 30 print0or1 >> putStrLn ""