static <A> int smartIndexOfPred(L<A> l, IPred<A> pred) {
  ret smartIndexOfPred(l, pred, 0);
}

static <A> int smartIndexOfPred(L<A> l, IPred<A> pred, int i) {
  int n = l(l);
  for (; i < n; i++)
    if (pred.get(l.get(i)))
      ret i;
  ret n;
}