static S[] toStringArray(Collection<S> c) {
  S[] a = new S[l(c)];
  Iterator<S> it = c.iterator();
  for (int i = 0; i < l(a); i++)
    a[i] = it.next();
  ret a;
}

static S[] toStringArray(O o) {
  if (o instanceof S[])
    return (S[]) o;
  else if (o instanceof Collection)
    return toStringArray((Collection<S>) o);
  else
    throw fail("Not a collection or array: " + getClassName(o));
}