anchor.diff:  
   %% @private
   -spec handle_info(term(), #state{}) -> {noreply, #state{}}.
  +handle_info(log, #state{ads=Ads}=State) ->
  +    %% Print number of enabled ads.
  +    {ok, AdList} = lasp:query(Ads),
  +    Size = sets:size(AdList),
  +
  +    lager:info("Enabled advertisements: ~p", [Size]),
  +
  +    %% Schedule advertisement counter impression.
  +    schedule_logging(),
  +
  +    {noreply, State};
   handle_info(Msg, State) ->
       lager:warning("Unhandled messages: ~p", [Msg]),
       {noreply, State}.
  
positive.code: -include("lasp.hrl").
  
  %% Macros.
  
  %% State record.
  -record(state, {actor}).
  
  -record(ad, {id, image, counter}).
  
  
negative.code: -behaviour(gen_server).
  
  %% API
  -export([start_link/0,
           trigger/3]).
  
  %% gen_server callbacks
  -export([init/1,
  