anchor.diff:          }
   
       /// Read all events from a mailbox
  -    let read (mb : Mailbox<_>) = mb.Read
  +    let read (mb : Mailbox<_>) = async { return  mb.Read () |> Feed.discardFuture }
   
       /// Discard all events currently in mailbox
       let clear (mb : Mailbox<_>) = mb.Clear
  
positive.code:         
          type MailTrigger = delegate of obj * EventArgs -> unit
  
          let inline read' (m : Ref<Feed<'e> * Feed<'e>>) =
              async {
                  let (inc, out) = !m
                  return Feed.combine inc out
              }
  
          let inline push' time evt (trigger : Event<MailTrigger, EventArgs>) (expire : Expire)  (m : Ref<Feed<'e> * Feed<'e>>) () : unit =
              let (inc, out) = !m
              match expire, Feed.tryHead (Feed.time out) with
              | After _, None -> 
  
negative.code:             | _ -> m := (Feed.Internal.unsafePush time evt inc, Feed.empty)
              trigger.Trigger(null, null)
                      
          let post mLock clock trigger expire evts evt =
              lock mLock (fun () -> let time = Clock.nowSynced clock in push' time evt trigger expire evts)
  
          let dropAll mLock (evts : Ref<Feed<'e> * Feed<'e>>) =
              async { return lock mLock (fun () -> evts := (Feed.empty, Feed.empty)) }
  