Hello,
I did not understand the example you posted, as it contains functions
that are not defined, but here is something you can do (this is using
monadLib, but something like that should probably work with the
libraries distributed with GHC). Letme know if this helps.
-Iavor
import Monad.StateT
import Monad.Id
import Random
type M = StateT (StdGen,[Int]) Id
randomItem :: M ()
randomItem = do (g,xs) <- peek
let (x,g') = random g
poke_ (g',mod x 5 : xs)
needMoreItems :: M Bool
needMoreItems = do (_,xs) <- peek
return (sum xs < 50)
whileM p b = do x <- p
if x then b >> whileM p b else return ()
test = do g <- newStdGen
print $ runId $ evalState (g,[])
$ do whileM needMoreItems randomItem
(_,xs) <- peek
return xs
On 11/22/05, Yitzchak Gale
Hi Iavor,
Just to clarify, I wasn't suggesting that the the monad is strict in the state component, but rather that it is strict in the pair containing the result and the state.
Does this help in the "createItems" examples I sent to Udo in the previous post?
Thanks, Yitz