anchor.diff:      type Visualizer (rootExprs: UExprT list) =
   
           let arrayNDManikins = ResizeArray<VisArrayNDManikin> ()
  +        let srcEdges = Dictionary<UExprT * int, Edge> ()
   
           let graph = Graph ("UExpr")
  +        let viewer = new GViewer(Dock=DockStyle.Fill, 
  +                                 PanButtonPressed=true, ToolBarIsVisible=false)
   
           let mutable ids = 0
           let newId () =
  
positive.code:             form.WindowState <- System.Windows.Forms.FormWindowState.Maximized
  
              // graph viewer
              let viewer = new GViewer(Graph=graph, Dock=DockStyle.Fill)
              viewer.PanButtonPressed <- true
              viewer.ToolBarIsVisible <- false
              form.Controls.Add viewer
  
              // splitter ArrayNDManikins / MemManikins
  
negative.code:                 resLabelNode.Label.FontColor <- Color.White
                  newEdge resNode resLabelNode "" |> ignore
  
          /// adds manikin information
          member this.AddManikins (euId: int) (uExpr: UExprT) 
                                  (trgtManikins: Map<string, ArrayNDManikinT>) 
                                  (srcManikins: ArrayNDManikinT list) =
              match nodeForExpr.TryFind uExpr with
              | Some node -> nodeForEuId.[euId] <- node
              | None -> ()
  
              for KeyValue(ch, manikin) in trgtManikins do
                  arrayNDManikins.Add {Manikin=manikin; EuId=euId; UExpr=uExpr; Relation=Target ch} 
              for src, manikin in List.indexed srcManikins do
                  arrayNDManikins.Add {Manikin=manikin; EuId=euId; UExpr=uExpr; Relation=Src src}
  
          /// shows the graph
          member this.Show () = 
              // add execution unit id to nodes
              for KeyValue(euId, node) in Map.ofDictionary nodeForEuId do
                  node.LabelText <- sprintf "%d: %s" euId node.LabelText
  
              // form
              let form = new System.Windows.Forms.Form(Text=graph.Label.Text, 
                                                       Width=1000, Height=600)
  