tjay.dreaming:
> Thanks for the demo. I don't actually understand what's going on yet,
> but your code doesn't really use a global variable, does it? From
> what I can understand, the main function is passing the State to the
> other functions.
Right, via the monad. The monad does all the threading.
>
> I think I was careless about mixing "IO functions" and normal
> functions. Now that I think about it, my "global variable" really
> should only be available to IO functions, so the following should be
> just fine:
>
> ----------------------------------------------------------
> module Global where
>
> import Data.IORef
>
> theGlobalVariable = newIORef []
>
> testIt = do ref <- theGlobalVariable
> original <- readIORef ref
> print original
> writeIORef ref [1,2,3]
> new <- readIORef ref
> print new
> ----------------------------------------------------------
>
> I've got a lot to learn about Haskell...
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
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