[Haskell-cafe] Beginner: IORef constructor?

[TJ]

Donald:
> Now, if you wanted to pass that ref to other functions, you'd have to
> thread it explicitly -- unless you store it in a state monad :)
>
>     i.e. do ref <- theGlobalVariable
>             ...
>             .. f ref
>             ...
>
>       f r = do
>             ...
>             .. g r
>             ...
>
> I kind of jumped ahead that step, and went straight to the implicitly
> threaded version.
>
> -- Don
>

Tested my code again and it doesn't work as expected. I don't
understand what "threading" means, but is that the reason I can't have
this:

----------------------------------------------------------
module StateTest where

import Data.IORef

theGlobalVariable = newIORef []

modify1 = do ref <- theGlobalVariable
             original <- readIORef ref
             print original
             writeIORef ref $ original ++ [1]
             new <- readIORef ref
             print new

modify2 = do ref <- theGlobalVariable
             original <- readIORef ref
             print original
             writeIORef ref $ original ++ [2]
             new <- readIORef ref
             print new

doIt = do modify1
          modify2
----------------------------------------------------------

TJ