ck :: Dist a -> R a
-- pick d = do {p <- Random.randomRIO (0,1); return (selectP p d)}
pick d = System.Random.randomRIO (0,1) >>= return . selectP d


pick :: Dist a -> R a
pick d = System.Random.randomRIO (0,1) >>= return . selectP d
pick d = System.Random.randomRIO (0,1) >>= return . selectP d