sclass FPSCounter {
  new Timestamp started;
  double counter;
  
  synchronized void inc() { counter++; }

  synchronized double get() {
    ret doubleRatio(counter, secondsSinceStart());
  }
  
  synchronized bool isEmpty() { ret counter == 0; }
  
  double secondsSinceStart() { ret elapsedSeconds(started); }
  
  synchronized void reset {
    started = tsNow();
    counter = 0;
  }
}