static <A> LPair<DoubleRange, A> concatenateAdjacentDoubleRanges(LPair<DoubleRange, A> l) {
  new LPair<DoubleRange, A> out;
  fOr (p : l)
    if (concatenatableRanges(pairA(last(out)), p.a) &&
      eq(pairB(last(out)), p.b))
      replaceLast(out, pair(joinDoubleRanges(pairA(last(out)), p.a), p.b);
    else
      out.add(p);
  ret out;
}