extensible-effects-concurrent-0.9.2: examples/example-4/Main.hs

module Main where

import           Control.Eff
import           Control.Eff.Lift
import           Control.Eff.Concurrent
import           Data.Dynamic
import           Control.Concurrent
import           Control.DeepSeq

main :: IO ()
main = defaultMain
  (do
    lift (threadDelay 100000) -- because of async logging
    firstExample forkIoScheduler
    lift (threadDelay 100000) -- ... async logging
  )
    -- The SchedulerProxy paremeter contains the effects of a specific scheduler
    -- implementation.

newtype WhoAreYou = WhoAreYou ProcessId deriving (Typeable, NFData)

firstExample :: (HasLoggingIO q) => SchedulerProxy q -> Eff (Process q ': q) ()
firstExample px = do
  person <- spawn
    (do
      logInfo "I am waiting for someone to ask me..."
      WhoAreYou replyPid <- receiveMessageAs px
      sendMessageAs px replyPid "Alice"
      logInfo (show replyPid ++ " just needed to know it.")
    )
  me <- self px
  sendMessageAs px person (WhoAreYou me)
  personName <- receiveMessageAs px
  logInfo ("I just met " ++ personName)