broadcasting.hs

import Data.Monoid
import Control.Concurrent
import qualified Control.Concurrent.Broadcast as Broadcast

biglog n = do
  if n == 100000 then pure n
    else print n >> biglog (n + 1)

main = do

  global_bc <- Broadcast.new -- main thread
  print_bc <- Broadcast.new -- thread with printing

  -- awake all global-listeners
  Broadcast.broadcast global_bc ()

  forkIO $ do
      -- listen broadcast from main thread
      Broadcast.listen global_bc
      -- run a long computation
      n <- biglog 0
      -- if this computation ended early than hitiing timout,
      -- broadcast about computed value
      Broadcast.broadcast print_bc n

  threadDelay 1000000
  Broadcast.tryListen print_bc >>= \v -> case v of
    Just n -> print $ "managed: " <> (show n)
    Nothing -> print "interrupted!"