anchor.diff:  
   %% @doc Return the number of pieces for torrent Id
   %% @end
  --spec num_pieces(integer()) -> {value, integer()}.
  +-spec num_pieces(integer()) -> {value, integer()} | not_found.
   num_pieces(Id) ->
       gen_server:call(?SERVER, {num_pieces, Id}).
   
  
positive.code: state_change(_Id, []) ->
      ok;
  state_change(Id, [What | Rest]) ->
      [T] = ets:lookup(?TAB, Id),
      New = case What of
                unknown ->
  
negative.code:     Q = all(#torrent.id),
      {reply, Q, S};
  handle_call({num_pieces, Id}, _F, S) ->
      Reply = case ets:lookup(?TAB, Id) of
  		[R] -> {value, R#torrent.pieces};
  		[] ->  not_found
  	    end,
      {reply, Reply, S};
  handle_call({statechange, Id, What}, _F, S) ->
      Q = state_change(Id, What),
      {reply, Q, S};
  