On Tue, Jun 9, 2009 at 16:14, Daniel Fischer<daniel.is.fischer@web.de> wrote:
> If you're doing much with random generators, wrap it in a State monad.

To avoid reinventing the wheel one can use excellent package available
on Hackage:
http://hackage.haskell.org/cgi-bin/hackage-scripts/package/MonadRandom

> The die function simulates the roll of a die, picking a number between 1 and 6, inclusive, and returning it in the Rand monad.
> Notice that this code will work with any source of random numbers g.
>
> die :: (RandomGen g) => Rand g Int
> die = getRandomR (1,6)
>
> The dice function uses replicate and sequence to simulate the roll of n dice.
>
> dice :: (RandomGen g) => Int -> Rand g [Int]
> dice n = sequence (replicate n die)
>
> To extract a value from the Rand monad, we can can use evalRandIO.
>
> main = do
>   values <- evalRandIO (dice 2)
>   putStrLn (show values)

Best regards

Krzysztof Skrzêtnicki

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