static bool allEq(O... l) {
  if (empty(l)) true;
  int n = l(l);
  O o = l[0];
  for (int i = 1; i < n; i++)
    if (neq(l[i], o)) false;
  true;
}

static <A> bool allEq(Iterable<A> l) {
  var it = iterator(l);
  if (!it.hasNext()) true;
  A o = it.next();
  while (it.hasNext())
    if (neq(it.next(), o)) false;
  true;
}