anchor.diff:        /* TODO */
   
         $result =
  -         $f.forSome
  +         ($f.result).forSome
            (
               root_node.oneOf
               (
                  MODEL.get_type_as_relation("node").in
                  (
  -                  VARIABLE_SET.get_variable($ps).join
  +                  VARIABLE_SET.get_variable(($ps.text)).join
                     (
                        MODEL.get_predicate_as_relation("start_node")
                     )
  
positive.code:    {
        /* TODO */
        $result =
           $bl_formula.forAll
           (
              next_state.in
              (
  
negative.code: ;
  
  bl_eg_operator [Variable current_state]
     returns [Formula result]
  
     @init
     {
  