Re: [Haskell-beginners] Just how unsafe is unsafe

8 Feb 2009


      Excerpts from Andrew Wagner's message of Thu Feb 05 15:11:17 -0600 2009:
...
My question is, to what extent is this true?
You can completely destroy the soundness of the type system:

    import Data.IORef
    import System.IO.Unsafe
    import Control.Monad

    cast :: a -> b
    cast x = f where
     f = unsafePerformIO $ do
         writeIORef r [x]
         b <- liftM head $ readIORef r
         return b

Austin

Re: [Haskell-beginners] Just how unsafe is unsafe

Austin Seipp