Re: [Haskell-beginners] IO vars

On 29 August 2012 10:21, Corentin Dupont wrote:

*f,g :: IO () f = withFile "toto" WriteMode (flip hPutStr "42") g = withFile "toto" ReadMode hGetLine >>= (\s -> putStrLn $ "Answer:" ++ s) main = f >> g*

Is it possible to do the same without files (the types must remain IO())?

One can use an IORef to get a similar effect. import Data.IORef import System.IO.Unsafe {-# NOINLINE toto #-} toto :: IORef String toto = unsafePerformIO (newIORef "") f,g :: IO () f = writeIORef toto "42" g = readIORef toto >>= (\s -> putStrLn $ "Answer:" ++ s) main = f >> g HTH, Ozgur