// assigns probability pStart for first element, pEnd for last element

//   (rest linearly interpolated)

//

// f may return an instance of IProbabilistic (or a normal Runnable)

static <A> void probabilisticForEach(IProbabilisticScheduler scheduler, double pStart, double pEnd, Cl<A> l, IVF1<A> f) {

  if (scheduler == null || f == null) ret;

  probabilisticForEach(scheduler, pStart, pEnd, iterator(l), 0, l(l), 1.0, f);

}

static <A> void probabilisticForEach(IProbabilisticScheduler scheduler, double pStart, double pEnd, Iterator<A> it, int i, int n, double myProb, IVF1<A> f) {

  assertTrue(pEnd <= pStart);

  if (scheduler == null || f == null || !it.hasNext()) ret;

  // get element

  A a = it.next();

  // calculate probability for element

  double p = blend(pStart, pEnd, doubleRatio(i, n-1));

  // run client function

  scheduler.at(new Runnable {

    run { f.get(a); }

    toString { ret formatFunctionCall(f, a); }

  });

  // schedule next element at lower probability

  scheduler.atRelative(doubleRatio(p, myProb), ->

    probabilisticForEach(scheduler, pStart, pEnd, it, i+1, n, p, f));

}