anchor.diff:              Error
       end.
   
  -ec2_tagged_instances_get_entries(Tags, Filter, Config) ->
  -    case erlcloud_ec2:describe_tags([{resource_type, ["instance"]} |
  -                                     Filter], Config) of
  -        {ok, EC2Tags} ->
  -            {ok, process(Tags, EC2Tags, tag)};
  -        {error, _} = Error ->
  -            Error
  -    end.
  -
   ec2_tagged_instances_get(#state{tags = ?NULL_EXPRESSION} = State) ->
       {ok, false, State};
  -ec2_tagged_instances_get(#state{ec2_config = Config,
  +ec2_tagged_instances_get(#state{ec2_instances = EC2Instances,
                                   ec2_tagged_instances = OldResult,
  -                                tags = Tags,
  -                                tags_filter = Filter} = State) ->
  -    case ec2_tagged_instances_get_entries(Tags, Filter, Config) of
  -        {ok, OldResult} ->
  +                                tags = Tags} = State) ->
  +    case process(Tags, EC2Instances, tag) of
  +        OldResult ->
               {ok, false, State};
  -        {ok, NewResult} ->
  -            {ok, true, State#state{ec2_tagged_instances = NewResult}};
  -        {error, _} = Error ->
  -            Error
  +        NewResult ->
  +            {ok, true, State#state{ec2_tagged_instances = NewResult}}
       end.
   
   update_from_instance(Instance, Hosts) ->
  
positive.code: process_filter(Tags, EC2Tags, tag) ->
      orddict:filter(fun(_, TagL) ->
          % do any of the tags for an instance match a single requirement
          lists:any(fun(#ec2_tag{key = Key, value = Value}) ->
              case orddict:find(Key, Tags) of
                  {ok, []} ->
                      true;
  
negative.code:                          GroupsExpressionTree == ?NULL_EXPRESSION ->
                      {stop, {error, null_selection}};
                  {ok, GroupsExpressionTree} ->
                      case do_discover(#state{ec2_config = Config,
                                              groups = GroupsExpressionTree,
                                              tags = TagsExpressionTree,
                                              nodes = [],
                                              connect = Connect}) of
                          {ok, #state{}} = Success ->
  