eeoam:
> H|i,
>
> Does anyone know of a simple and straightforward way to use global
> variables in Haskell?
>
> E.
As other posters have said, you'll need to state what you're trying to
do. For one particular case, that of a program that needs access to
state over its lifetime, State monads are used. Here's a small example:
-- import global variable support
import Control.Monad.State
-- declare our global variables. here we just have a single Int
type Global = Int
-- initialise them on startup
main = print (evalState main' 7) -- 7 is the default value
-- code that runs with access to these globals, note that its type
-- indicates that it uses globals:
main' :: State Global Int
main' = do
i <- get -- get and modify the global a few times
put (i ^ 2)
modify $ \i -> i `div` 2
i <- get
return i
We can run this:
$ runhaskell A.hs
24
-- Don
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