Re: [Haskell-cafe] How to update the RNG per call (State monad) when generating QuickCheck arbitraries?

Oh thanks, hold on I'd like to have the genArray call generating distinctive results in one IO execution (meaning when I load the .lhs file in ghci): Prelude> genArray [ThingK True,Thing1 False] and when calling immediately again e. g. Prelude> genArray [Thing1 True] By now I only get one and the same again, i. e.: Prelude> genArray [ThingK True] Prelude> genArray [ThingK True] ... so I thought an adaptation of the `runTwoRandoms` approach as described in the RWH book could help. In other words the genArray should have similar behaviour as e. g. a `runOneRandom` function defined like:

getOneRandom :: Random a => RandomState a getOneRandom = getRandom

runOneRandom :: IO Int runOneRandom = do oldState <- getStdGen let (result, newState) = S.runState getOneRandom oldState setStdGen newState return result

... the rest of the code as in my first post... Testing it, different numbers expected as the RNG is updated each call: Prelude> runOneRandom 2033303743 Prelude> runOneRandom -566930973 ... Cheers Daniel 2011/4/26 Bryan O'Sullivan :

On Tue, Apr 26, 2011 at 3:04 AM, Daniel Kahlenberg wrote:

...

Thought getRandom function would be the best place to inject my unGen function call, but cannot get it to type-check:

You haven't described what it is you're actually trying to do, and I'm afraid your code doesn't help to understand that.