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
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