persistable sclass BoolVar {

  bool a; // you can access this directly if you use one thread

  *() {}

  *(bool *a) {}

  public synchronized void set(bool v default true) {

    if (v != a) {

      a = v;

      notifyAll();

    }

  }

  public synchronized bool get() { ret a; }

  //public synchronized bool has() { true; }

  public void clear aka unset() { set(false); }

  bool waitUntilTrue () { ret waitForValue(true); }

  bool waitUntilFalse() { ret waitForValue(false); }

  bool waitUntilTrue (double timeoutSeconds) { ret waitForValue(timeoutSeconds, true); }

  bool waitUntilFalse(double timeoutSeconds) { ret waitForValue(timeoutSeconds, false); }

  synchronized bool waitForValue(bool wantedValue) ctex {

    while (a != wantedValue)

      wait();

    ret a;

  }

  synchronized bool waitForValue(double timeoutSeconds, bool wantedValue) ctex {

    if (timeoutSeconds == infinity())

      ret waitForValue(wantedValue);

    long destTime = sysNowPlusSeconds_noPing(timeoutSeconds), remainingTime;

    while (a != wantedValue

      && (remainingTime = destTime-sysNow_noPing()) > 0)

      wait(remainingTime);

    ret a;

  }

  public synchronized bool getAndSet(bool b) {

    var value = a;

    set(b);

    ret value;

  }

  public synchronized bool waitUntilTrueAndClear() {

    if (!waitUntilTrue()) false;

    set(false);

    true;

  }

  public synchronized bool waitUntilTrueAndClear(double timeoutSeconds) {

    if (!waitUntilTrue(timeoutSeconds)) false;

    set(false);

    true;

  }

  O mutex() { this; }

}