static <A, B> Map<A, B> replaceValuesWith(Map<A, B> map, B value) {
  Map<A, B> m = similarEmptyMap(map);
  for (A a : keys(map))
    m.put(a, value);
  ret m;
}

static <A, B> Map<A, B> replaceValuesWith(B value, Map<A, B> map) {
  ret replaceValuesWith(map, value);
}