anchor.diff:      let printEdge { Pre = s; Post = t; Cmd = vf } =
           hsep [ s |> sprintf "v%A" |> String
                  String "->"
  -               t |> sprintf "v%A" |> String ]
  +               t |> sprintf "v%A" |> String
  +               vf |> printVFunc |> printLabel ]
           |> withSemi
   
       /// <summary>
  
positive.code:     ///     A pretty-printer <c>Command</c> representing the node.
      /// </returns>
      let printNode id view =
          hsep [ sprintf "v%A" id |> String
                 squared (hsep [ String "label"
                                 String "="
                                 view |> printGView |> ssurround "\"" "\"" ])]
          |> withSemi
  
      /// <summary>
  
negative.code: 
  module Pretty =
      /// <summary>
      ///     Prints a GraphViz label directive.
      /// </summary>
      /// <param name="labelCmd">
      ///     The pretty-printer command to use as the label.
      /// </param.
      /// <returns>
      ///     A pretty-printer command representing
      ///     [label = "<paramref name="labelCmd" />"].
      /// </returns>
      let printLabel labelCmd =
          [ String "label"
            String "="
            labelCmd |> ssurround "\"" "\"" ]
          |> hsep |> squared
      
      /// <summary>
      ///     Prints a node.
      /// </summary>
      /// <param name="id">
  