anchor.diff:  
   %% debug.
   -export([active/0,
  +         active/1,
            passive/0]).
   
   %% gen_server callbacks
  
positive.code: %% @doc Debugging.
  active() ->
      gen_server:call(?MODULE, active, infinity).
  
  %% @doc Debugging.
  passive() ->
  
negative.code:             {reply, {error, no_available_slots}, State}
      end;
  
  handle_call({active, Tag},
              _From,
              #state{reserved=Reserved}=State) ->
      lager:info("Reserved dictionary: ~p", [Reserved]),
      Result = case dict:find(Tag, Reserved) of
          {ok, {Peer, _, _}} ->
              {ok, Peer};
          {ok, undefined} ->
              {ok, undefined};
          error ->
              error
      end,
      {reply, Result, State};
  
  handle_call(passive, _From, #state{passive=Passive}=State) ->
      {reply, {ok, Passive}, State};
  