anchor.diff:                          for family in children.other do
                               handle family
           res.ToArray()
  -    
  +
  +    let leftSide = ref _leftSide
  +    let numToString = ref _numToString
  +
       let checkFamilyIsGivenNonterminal nonterminalInd (family : Family) = 
  -        match leftSide with 
  +        match !leftSide with 
           | None -> failwith "leftSide is not specified"
           | Some ls -> nonterminalInd = ls.[family.prod]
   
  
positive.code: type ErrorDictionary<'TokenType> = Dictionary<Family, ErrorNode<'TokenType>>
  
  [<AllowNullLiteral>]
  type Tree<'TokenType> (tokens : array<'TokenType>, root : AstNode, rules : int[][], leftSide : array<int> option, numToString : (int -> string) option) =
      let rootFamily, isEpsilonTree =
          match root with
          | :? AST as ast -> ast, false
  
negative.code:         | Some ind -> ind
  
      let getNonterminalStringByProd prod =
          match !numToString with
          | None -> failwith "numToString is not specified"
          | Some nts ->
              match !leftSide with 
              | None -> failwith "leftSide is not specified"
              | Some ls -> nts <| ls.[prod]
  
  