type CounterMessage =
  | Update of float
  | Reset

let counter = MailboxProcessor.Start(fun agent ->
    let rec loop sum count = async {
      let! msg = agent.Receive()
      match msg with
      | Reset -> return! loop 0.0 0.0
      | Update value ->
          let sum, count = sum + value, count + 1.0
          printfn "Average: %f" (sum / count)
          do! Async.Sleep(1000)
          return! loop sum count
    }
    loop 0.0 0.0)


couter.Post(Update, 10.0)
couter.Post(Reset)