anchor.diff:          List.append
               (nodes |> Map.toList |> List.map (uncurry printNode))
               (edges |> List.map printEdge)
  -        |> vsep
  +        |> ivsep |> braced
   
       /// <summary>
       ///     Prints a <c>Graph</c>.
  
positive.code:     let printEdge { Pre = s; Post = t; Cmd = vf } =
          hsep [ s |> sprintf "V%A" |> String
                 String "->"
                 t |> sprintf "V%A" |> String
                 String ";"]
  
      /// <summary>
      ///     Prints a <c>Subgraph</c>.
  
negative.code:     let printGraph { Name = name; Contents = sg } =
          hsep [ String "digraph"
                 String name
                 sg |> printSubgraph ]
  
  (*
   * Helper functions
  