// null elements are not supported

static <A extends Comparable<A>, B extends Iterable<A>> ItIt<A> intersectMultipleSortedCollectionsI(L<B> collections) {

  if (empty(collections)) ret emptyItIt();

  ret iteratorFromFunction_if0(new IF0<A> {

    Iterator<A>[] iterators = makeIteratorArray(collections);

    int n = iterators.length;

    A[] objects = (A[]) new Comparable[n];

    bool done;

    {

      // Grab first round of objects

      for i to n:

        if (step(i)) break;

    }

    // returns true if done

    bool step(int i) {

      if (!iterators[i].hasNext())

        { set done; true; }

      else {

        objects[i] = iterators[i].next();

        ifdef intersectMultipleSortedCollectionsI_debug

          print("Stepped " + (i+1) + " => " + objects[i]);

        endifdef

      }

      false;

    }

    public A get() {

      while ping (true) {

        if (done) null;

        // get min & max

        A min = objects[0], max = objects[0];

        for (int i = 1; i < n; i++) {

          A o = objects[i];

          if (min.compareTo(o) > 0) min = o;

          if (max.compareTo(o) < 0) max = o;

        }

        // min = max? then return element

        ifdef intersectMultipleSortedCollectionsI_debug

          print("min=" + min + ", max=" + max);

        endifdef

        if (min == max) {

          for i to n: if (step(i)) break;

          ret min;

        }

        // advance all to max

        for i to n:

          while (objects[i].compareTo(max) < 0)

            if (step(i)) null;

      }

    }

  });

}