anchor.diff:      Added = sets:subtract(FilesSet, S#state.fileset),
       Removed = sets:subtract(S#state.fileset, FilesSet),
       NewState = S#state{fileset = FilesSet},
  -    {Added, Removed, NewState}.
  +    {ok, Added, Removed, NewState}.
  
positive.code: start_link() ->
      gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).
  
  watch_dirs() ->
      gen_server:cast(dirwatcher, watch_directories).
  
  dir_watched() ->
      gen_server:call(dirwatcher, dir_watched).
  
  
negative.code: %%--------------------------------------------------------------------
  
  %% Operations
  watch_directories(S) ->
      {ok, A, R, N} = scan_files_in_dir(S),
      lists:foreach(fun(F) ->
  			  torrent_manager:start_torrent(F)
  		  end,
  		  sets:to_list(A)),
      lists:foreach(fun(F) -> torrent_manager:stop_torrent(F) end,
  		  sets:to_list(R)),
      N.
  
  empty_state() -> sets:new().
  
  