Hi,
I am using "pipes-concurrency" trying to model the following scenario: my
"source" pipe has type of
stream :: Producer InputData (StateT References IO) ()
where "References" is just a map that I accumulate while streaming the
source. Then I am following the "broadcast" example from the Tutorial
attempting to "fork" my flow into two branches:
main = do
(output1, input1) <- spawn unbounded
(output2, input2) <- spawn unbounded
a1 <- async $ do
execStateT (runEffect $ stream >-> toOutput (output1 <> output2))
emptyTables
performGC
a2 <- async $ do
withFile "/tmp/geo/smart-grouping.xml" WriteMode $ \h -> do
evalStateT (runEffect $ groupSmart (fromInput input1) >-> toHandle h)
??? -- what to put here?
hFlush h
performGC
a3 <- async $ do
withFile "/tmp/geo/damnGrouping.xml" WriteMode $ \h -> do
evalStateT (runEffect $ groupDamn (fromInput input2) >-> toHandle h)
???
hFlush h
performGC
mapM_ wait [a1,a2,a3]
I would like my branches to use the information from the source's StateT,
however following the types, it looks like I have to provide each branch
with the initial (empty?) state.
How do I share the state between the source and the forked branches? Or how
do I model this situation correctly?
Cheers,
Alexey.
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