anchor.diff:  -export([start_link/0,
            start_link/1,
            get/1,
  +         iterator/0,
  +         iterator/1,
            iterator/2,
            iterate/1,
            iterator_prefix/1,
  
positive.code:     It#metadata_iterator{done=true,
                           pos=undefined,
                           obj=undefined};
  next_iterator(It, {[Next], Cont}) ->
      It#metadata_iterator{pos=Cont,
                           obj=Next}.
  
negative.code: 
  next_iterator(It=#metadata_iterator{done=true}) ->
      It;
  next_iterator(It=#metadata_iterator{prefix=undefined,match=undefined,tab=Tab,pos=Pos}) ->
      next_iterator(It, ets:next(Tab, Pos));
  next_iterator(It=#metadata_iterator{prefix=undefined,pos=Pos}) ->
      next_iterator(It, ets:select(Pos));
  next_iterator(It=#metadata_iterator{pos=Pos}) ->
      next_iterator(It, ets:match_object(Pos)).
  
  