anchor.diff:  
       type RoomActorState = {RoomName: RoomName; ConnectedUsers: Map<UserName,UserConnection>}
       let roomActor initState (mailbox:Actor<RoomMessage>) =
  -        let notifyUsers state notification =
  -            let userActors = state.ConnectedUsers |> Map.toList |> List.map snd
  +        let notifyUsers state notification userName =
  +            let userActors =
  +                state.ConnectedUsers
  +                |> Map.filter (fun k b -> k <> userName)
  +                |> Map.toList
  +                |> List.map snd
               printfn "Users in room: %A" userActors
               userActors |> List.iter (fun userActor -> userActor.Notify notification)
   
  
positive.code:                 let sender = mailbox.Sender()
                  match state', message with
                  | Some (_, userMonitor), Connect(x,y) ->
                      let user = userMonitor.Connect x y
                      sender <! user
                  | Some (roomMonitor, _), GetRoomList ->
                      let roomList = roomMonitor.GetRoomList()
  
negative.code:             let! message = mailbox.Receive()
              match message with
              | UserSays (message, userName) ->
                  printfn "notifying all the users %A" message
                  notifyUsers state (UserSaid (userName, message, (state.RoomName))) userName
                  printfn "Notified everyone"
                  return! loop state
              | Join(userConnection) ->
                  printfn "In room joining %A" message
                  notifyUsers state (UserJoinedRoom (state.RoomName, userConnection.UserName)) userConnection.UserName
                  printfn "Hello"
                  return! loop {state with ConnectedUsers = state.ConnectedUsers |> Map.add userConnection.UserName userConnection}
          }
  