anchor.diff:                  this.Window.AddStock, AddStockToPriceChart
               ]
               |> List.map(fun(button, value) -> button.Click |> Observable.mapTo value)
  -
  -        buttonClicks @ 
  -        [ 
  -            this.Window.X.PreviewTextInput 
  -                |> Observable.merge this.Window.Y.PreviewTextInput
  -                |> Observable.map (fun x -> XorYChanging(x.Text, fun() -> x.Handled <- true))
  -
  -            this.Window.Y.TextChanged |> Observable.map(fun _ -> YChanged(this.Window.Y.Text))
  +                 
  +            yield this.Window.Y.TextChanged |> Observable.map(fun _ -> YChanged(this.Window.Y.Text))
           ] 
   
       override this.SetBindings model = 
           Binding.FromExpression 
               <@ 
  -                this.Window.Op.ItemsSource <- model.AvailableOperations 
  -                this.Window.Op.SelectedItem <- model.SelectedOperation
  +                this.Window.Operation.ItemsSource <- model.AvailableOperations 
  +                this.Window.Operation.SelectedItem <- model.SelectedOperation
                   this.Window.X.Text <- string model.X
                   this.Window.Y.Text <- string model.Y 
                   this.Window.Result.Text <- string model.Result 
  
positive.code:         | Hex1 -> Sync this.Hex1
          | Hex2 -> Sync this.Hex2
          | AddStockToPriceChart -> Async this.AddStockToPriceChart
          | XorYChanging(newValue, cancel) -> Sync(this.InputChanging(newValue, cancel))
          | YChanged text -> Sync(this.YChanged text)
  
      member this.Calculate model = 
  
negative.code:             )
          }
  
      member this.YChanged text model = 
          Debug.WriteLine("Start YChanged.")
          if text <> "0"
  