sclass ProbabilisticList<A> extends AbstractList<A> {

  TreeSetWithDuplicates<Entry> entries = new(byProbability());

  bool verbose;

  // must be >= 0. probability 0 is never added

  double cutoffProbabilityOnAdd = 0;

  Comparator<Entry> byProbability() { ret (a, b) -> cmp(b.probability, a.probability); }

  persistable class Entry {

    double probability;

    A element;

    *(double *probability, A *element) {}

    toString {

      ret str(WithProbability(probability, element));

    }

  }

  public void add aka at(double probability, A element) {

    if (element == null) ret;

    if (probability <= cutoffProbabilityOnAdd) ret;

    entries.add(new Entry(probability, element));

  }

  A first() {

    Entry s = first(entries);

    ret s?.element;

  }

  void clear {

    entries.clear();

  }

  run {

    stepAll(this);

  }

  void run(int maxSteps) {

    stepMax(maxSteps, this);

  }

  void printStats() {

    Entry first = entries.first(), last = entries.last();

    Entry next = nextSteppable();

    print("ProbabilisticScheduler. "

      + nEntries(entries)

      + ", highest probability in queue: " + (first == null ? "-" : first.probability)

      + ", lowest probability in queue: " + (last == null ? "-" : last.probability)

      + ", cutoff probability: " + cutoffProbabilityOnAdd + "/" + cutoffProbabilityOnExecute

      + ", " + (next == null ? "done" : "next step: " + next.action));

  }

  // Get probability of this thread's Runnable.

  // Or 1.0 when we are coming from "outside" (so you don't _have_ to

  // run your first step through the scheduler).

  public double currentProbability aka current() {

    ret or(threadProbability!, 1.0);

  }

  /*IProbabilisticScheduler freeze() {

    double prob = currentProbability();

    ret new IProbabilisticScheduler {

      public void at(double probability, Runnable action) {

        ProbabilisticScheduler.this.at(prob*probability, action);

      }

      public double currentProbability() {

        ret prob;

      }

      public long stepCount() { ret stepCount; }

    };

  }*/

  double remainingProbability() {

    Entry s = nextSteppable();

    ret s == null ? 0.0 : s.probability;

  }

  public double lastExecutedProbability() { ret lastExecutedProbability; }

  public long stepCount() { ret stepCount; }

}