sclass TradingCandleMaker {
  settable double candleLength = 1; // in minutes
  
  new L<TradingCandle> candles;
  
  TradingCandle currentCandle() { ret last(candles); }  
  
  void add(double price, long timestamp) {
    if (needNewCandle(timestamp))
      candles.add(new TradingCandle);
    var c = currentCandle();
    c.addValue(price, new Timestamp(timestamp));
  }
  
  bool needNewCandle(long timestamp) {
    ret empty(candles)
      || timestamp >= currentCandle().startTime.plusSeconds(candleLength*60).unixDate();
  }
}