anchor.diff:  
           inherit Reader<'a[]>(out.Id)
   
  -        let addStream = Stream<_>(Failure [])
  -
           let streams = ResizeArray<Stream<'a>>()
   
           let update() =
  
positive.code:                 streams
              |> Result.Map (List.rev >> Array.ofList)
              |> out.Trigger
  
          do
              adder.stream.Subscribe(
                  function Success v -> Success v |> addStream.Trigger
                          | Failure _ -> ()
              ) |> ignore
  
  
          override this.Subscribe f = out.Subscribe f
  
negative.code:             match out.Latest with
              | Failure _ -> ()
              | Success xs -> Array.iter add xs
              adder.stream.Subscribe(function
                  | Failure _ -> ()
                  | Success init -> add init)
              |> ignore
              c.Container
  
          member this.Add = adder.stream :> Writer<'a>
  
          member this.AddRender f = adder.view f
  
  