Thanks for the tip, Ozgur. It worked for me. Is this what you had in mind, Ryan?
Michael ============== import Control.Monad.State.Lazy import Control.Monad import System.Random type GeneratorState = State StdGen data Craps a = Roll a | Win a | Lose a deriving (Show) genRandomR :: Random a => (a,a) -> GeneratorState a genRandomR = state . randomR rollDie :: GeneratorState Int rollDie = genRandomR (1,6) roll2Dice :: GeneratorState Int roll2Dice = liftM2 (+) rollDie rollDie f :: Craps [Int] -> GeneratorState (Craps [Int]) f (Roll []) = do g0 <- get let (throw1,g1) = runState roll2Dice g0 put g1 case throw1 of 2 -> return (Lose [throw1]) 3 -> return (Lose [throw1]) 7 -> return (Win [throw1]) 11 -> return (Win [throw1]) _ -> do g1 <- get let (throw2,g2) = runState roll2Dice g1 put g2 if throw2 == throw1 then do return (Win [throw1,throw2]) else if throw2 == 7 then do return (Lose [throw1,throw2]) else do f (Roll [throw1,throw2]) f (Roll z@(throw1:throws)) = do g0 <- get let (throw,g1) = runState roll2Dice g0 put g1 if throw == throw1 then do return (Win (z ++ [throw])) else if throw == 7 then do return (Lose (z ++ [throw])) else do f (Roll (z ++ [throw])) --- On Wed, 12/22/10, Ozgur Akgun <ozgurak...@gmail.com> wrote: From: Ozgur Akgun <ozgurak...@gmail.com> Subject: Re: [Haskell-cafe] Why is Haskell flagging this? To: "Ryan Ingram" <ryani.s...@gmail.com> Cc: haskell-cafe@haskell.org, "Daniel Fischer" <daniel.is.fisc...@googlemail.com> Date: Wednesday, December 22, 2010, 7:37 PM see also: http://hackage.haskell.org/packages/archive/mtl/latest/doc/html/Control-Monad-State-Lazy.html#v:state On 22 December 2010 20:02, Ryan Ingram <ryani.s...@gmail.com> wrote: Interesting. In that case, state f = StateT $ \s -> Identity (f s) allows "state" to replace "State" in that code. Ozgur -----Inline Attachment Follows----- _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
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