static java.util.Timer onValueChangeAndNow(int interval, final F0 f, fO onChange) {
  ret doEveryAndNow(interval, new Runnable {
    bool firstTime = true;
    O lastValue;
    
    public void run {
      O value = callF(f);
      if (firstTime || neq(value, lastValue)) {
        firstTime = false;
        lastValue = value;
        callF(onChange, value);
      }
    }
  });
}