static <A, B> L<WithProbability<B>> mapProbabilisticList(IF1<A, B> f, Iterable<WithProbability<A>> l) {
  ret map(l, a -> a == null ?: withProbability(a.probability(), f.get(a!)));
}

static <A, B> L<WithProbability<B>> mapProbabilisticList(Iterable<WithProbability<A>> l, IF1<A, B> f) {
  ret mapProbabilisticList(f, l);
}