static L<S> toLowerCase(L<S> strings) {
  new L<S> x;
  for (S s : strings)
    x.add(s.toLowerCase());
  ret x;
}

static S[] toLowerCase(S[] strings) {
  S[] x = new S[l(strings)];
  for (int i = 0; i < l(strings); i++)
    x[i] = strings[i].toLowerCase();
  ret x;
}

static S toLowerCase(S s) {
  ret s == null ? "" : s.toLowerCase();
}