static <A, B extends Number> A lowest(Map<A, B> map) {
  A best = null;
  Number bestScore = null;
  for (A key : keys(map)) {
    Number score = map.get(key);
    if (best == null || cmp(score, bestScore) < 0) {
      best = key;
      bestScore = score;
    }
  }
  ret best;
}

static <A> A lowest(Iterable<A> l, IF1<A, Number> f) {
  ret lowestByScoreFunction(l, f);
}