anchor.diff:  
   module ToDo
   
  -// NOTE: This is not meant to demonstrate the most concise or best way to
  -// program with WPF and choice streams.  This example overuses choice streams
  -// to show some more usage patterns.
  +// NOTES: This is not meant to demonstrate the most concise or best way to
  +// program with WPF and choice streams.  This example overuses choice streams to
  +// show some more usage patterns.  WPF is fundamentally an imperative UI
  +// framework and this example does not try to rewrite WPF as a more functional
  +// framework.  Some of the simple techniques in this example, such using an
  +// immutable list as the model and removing and adding all controls when the
  +// model changes, do not scale.  Consider those as exercises to fix.
   
   open Hopac
   open Hopac.Job.Infixes
  
positive.code: open Hopac.Extensions
  
  open System
  open System.Threading
  open System.Windows
  open System.Windows.Controls
  
negative.code: 
        let itemsAndCtrls =
          Stream.Var.tap itemsVar
          |> Stream.scanFromJob [] (fun oldItemsAndCtrls newItems -> onMain {
             let newCtrl item =
               let ctrl = ToDo.UI.ItemControl ()
  
  