anchor.diff:                                  else currentR := getNodeT !currentIndex
                                   currentIndex := !currentIndex + 1
                                   currentLabel := packLabel (rule) ((position) + 1)
  -                                if (!currentR).tree <> dummyAST.tree
  +                                if not <| obj.ReferenceEquals(!currentR, dummyAST)
                                   then currentN := getNodeP !currentLabel !currentN !currentR
                                   condition := false
                           else 
  
positive.code:         let dummyFam = Family()
          let currentN = ref <| dummyAST
          let currentR = ref <| dummyAST
   
          
          
  
negative.code:         let getNodeT index =
              if terminalNodes.Item index = Unchecked.defaultof<ExtensionTree>
              then
                  let tree = new TerminalNode(index)
                  let result = new ExtensionTree(packExtension index (index + 1), tree)
                  terminalNodes.Set index result
                  result
              else terminalNodes.Item index            
              
  