sclass PerSecondCounter {
  double interval = 1; // seconds
  long time = sysNow(), count, lastCount, lastDiff;
  
  *() {}
  *(double *interval) {}
  
  void inc() {
    ++count;
  }
  
  double get() {
    long diff = sysNow()-time;
    double fps = (count+lastCount)*1000.0/(diff+lastDiff);
    if (diff >= toMS(interval)) {
      lastDiff = diff;
      lastCount = count;
      time = sysNow();
      count = 0;
    }
    ret fps;
  }
}