anchor.diff:              let edges = gss.[getIndex2Vertex b].[getIndex1Vertex b].OutEdges
               edges.first <> Unchecked.defaultof<_> && (edges.first.Dest = e || (edges.other <> null && edges.other |> Array.exists (fun edge ->  edge.Dest = e)))
   
  -        let findTree prod extension (family : Family) =            
  +        let findTree extension (family : Family) =            
               let result = 
                   if astDictionary.ContainsKey extension
                   then
  
positive.code: 
          let findFamily prod (nodes : INode) extension : Family =
              let mutable result = None
              let res = ref <| null
              let exists = createdFamilies.[prod].TryGetValue(extension, res)
              if exists
              then 
  
negative.code:                     let value = new AST(family, null)
                      astDictionary.Add(extension, value)
                      value
              result
  
          let create label (u : int64<vertex>) (index : int) (ast : ExtensionTree) = 
  