svoid scorePtDistances(Scorer scorer, LPair<Pt> l, double maxDistanceAllowed) {
  fOr (Pair<Pt> p : l)
    if (p.a == null || p.b == null)
      scorer.addError();
    else
      scorer.add(1.0-ptDistance(p.a, p.b)/maxDistanceAllowed);
}