public Object parse(string str, Accion action)
 {
     LanguageData lenguaje = new LanguageData(gramatica);
     Parser p = new Parser(lenguaje);
     ParseTree s_tree = p.Parse(str);
     if (s_tree.Root != null)
     {
         ActionMaker act = new ActionMaker(s_tree.Root);
         act.escribir_arbol();
         return act.getEval(action);
     }
     return null;
 }