anchor.diff:                                                                                                              isContainPref (Some ast) astPrefix (Some wasAstStarts) None napref None wasAst wasFind))
                       then
                           errorEdges.Add(e, new ResizeArray<_>())
  -                        addPrefix errorEdges.[e] napref //added napref, which contain some error prefixes
  +                        addPrefix errorEdges.[e] napref
   
           buildErrors errorEdges
   
  
positive.code:                         (fun (lprefix:LabledPrefix<_>) -> match lprefix with
                                                              |Epsilon (epsGssv, epsPrefixes) -> epsGssv = gssVertex
                                                              | _ -> false)
                          curLevel) || curLevel = prefixesToAdd   //epsilon self arrow
              then curLevel.Add(Epsilon (gssVertex, prefixesToAdd))
  
          |Pref prefixToAdd -> 
  
negative.code:                 else ast.other <- Array.append ast.other [|newFamily|]
          | Some _ -> ()
  
      let rec addToNonTermEnds (curLevel:ResizeArray<LabledPrefix<_>>) (ast:AstNode) (tailLPrefixes:ResizeArray<LabledPrefix<_>>) (was:ResizeArray<ResizeArray<LabledPrefix<_>>>) =
          was.Add(curLevel)
          for curLPrefix in curLevel do
              match curLPrefix with
  