Add a `StateT` layer to each component's base monad. They will then
share that state. Here is an example:
import Control.Monad (forever)
import Control.Monad.Trans.State
import Pipes
producer :: Producer Int (StateT Int IO) r
producer = forever (do
n <- lift get
lift (put $! n + 1)
yield n )
consumer :: Consumer Int (StateT Int IO) r
consumer = forever (do
n <- await
lift (lift (print n))
lift (modify (+ 1)) )
main :: IO ()
main = evalStateT (runEffect (producer >-> consumer)) 0
That will print:
0
2
4
6
...
On 04/28/2015 09:36 PM, Ray Qiu wrote:
How to share state between pipes Consumers/Pipes without using ioref?
Thanks!
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