static L<IntRange> splitIntoRandomRanges(int approximateNumberOfRanges, IntRange base) {
  int i = base.start;
  new L<IntRange> out;
  double avgLength = doubleRatio(l(base), approximateNumberOfRanges);
  while (i < base.end) {
    int j = i+max(1, iround(random(avgLength*2)));
    out.add(intRange(i, j));
    j = i;
  }
  ret out;
}