anchor.diff:  
   namespace Nu
   open System
  +open System.Collections.Generic
   open System.IO
  -open System.Collections.Generic
  +open System.Threading
  +open System.Threading.Tasks
   open Prime
   
   /// The base component type of an Ecs.
  
positive.code:     abstract ProcessActualize : 'w Ecs -> 'w -> 'w
      default this.ProcessActualize _ world = world
  
  /// A system with zero to many components.
  and [<AbstractClass>] 'w SystemMany () =
      inherit System<'w> ()
  
negative.code:     let systemsUnordered = dictPlus [] : Dictionary<string, 'w System>
      let systemsOrdered = List () : (string * 'w System) List
      let correlations = dictPlus [] : Dictionary<Guid, string List>
      let pipedValues = dictPlus [] : Dictionary<Guid, obj>
  
      member internal this.Correlations 
          with get () = correlations
  
      member this.RegisterPipedValue<'a> key (value : 'a) =
          pipedValues.[key] <- (value :> obj)
  
      member this.UnregisterPipedValue key =
          pipedValues.Remove key
  
      member this.TryIndexPipedValue<'a> key =
          match pipedValues.TryGetValue key with
          | (true, value) -> Some (value :?> 'a)
          | (false, _) -> None
  
      member this.IndexPipedValue<'a> key =
          pipedValues.[key] :?> 'a
  
      member this.RegisterSystem systemName system =
          systemsUnordered.Add (systemName, system)
  