This is what I'd do:
{-# LANGUAGE NoMonomorphismRestriction #-}
module Counter where
import Control.Monad.State
main = runStateT procedure (0 :: Integer) >> return ()
incCounter = do
n <- get
modify (+1)
return n
execFile = do
n <- incCounter
liftIO $ putStrLn $ ("command --createfile=tempfile" ++ show n ++ ".tmp")
procedure = do
execFile
execFile
liftIO $ putStrLn "do something"
execFile
On Fri, Jul 22, 2011 at 3:10 AM, Davi Santos
Hello all, I have massive (parallel if possible) system calls to an external non-deterministic program. Each time it is executed, it creates a file depending on a command line option 'opt' (input files path, for example). How can I ensure the file name will be unique? maybe with a global counter? My temporary solution have been to use a large random number: ----------- mysteriousExecution :: String -> IO () mysteriousExecution opt = do number <- rand run $ "mysterious-command " ⊕ opt ⊕ " --create-file=" ⊕ number rand = do a ← getStdRandom (randomR (1,999999999999999999999999999999999)) ∷ IO Int let r = take 20 $ randomRs ('a','z') (mkStdGen a) ∷ String return r ======== I'm trying to avoid additional parameters to 'mysteriousExecution'. I tried a counter also (to replace rand), but I don't know how could I start it inside 'mysteriousExecution'. c ∷ IO Counter c = do r ← newIORef 0 -- start return (do modifyIORef r (+1) readIORef r) If somebody says everything is wrong, ok. I understand. 18 years of imperative programming world can damage the brain. Thanks _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners