static <A, B> Map<A, B> lookupToMap(Map<A, B> map, Collection<A> l) {
  new LinkedHashMap<A, B> out;
  if (l != null) for (A a : l)
    mapPut(out, a, map.get(a));
  ret out;
}

static <A, B> Map<A, B> lookupToMap(Collection<A> l, Map<A, B> map) {
  ret lookupToMap(map, l);
}