anchor.diff:      {ok, State}.
   
   
  -handle_event({transaction, Data}, LogFile) ->
  +handle_event({transaction, Data}, #state{log_file=LogFile}=State) ->
       LogEntry = string:join(
           [
               float_to_list(Data#transaction.timestamp),
  
positive.code:         ?LOG_FIELD_DELIMITER
      ),
      io:format(LogFile, "~s~n", [LogEntry]),
      {ok, LogFile};
  
  handle_event(_Event, LogFile) ->
      {ok, LogFile}.
  
  %% ============================================================================
  %% Internal
  
negative.code: -include("market_types.hrl").
  
  
  -record(state, {log_file :: pid()}).
  
  
  %% ============================================================================
  %% API
  %% ============================================================================
  