meta-for Range also as DoubleRange {
  sbool rangesOverlap(Range a, Range b) {
    ret intersectRanges(a, b) != null;
  }
}

sbool rangesOverlap(L<Range> l) {
  assertTrue(l(l) == 2); // TODO: more?
  ret rangesOverlap(first(l), last(l));
}