static <A> int indexOf(L<A> l, A a, int startIndex) {
  if (l == null) ret -1;
  int n = l(l);
  for (int i = startIndex; i < n; i++)
    if (eq(l.get(i), a))
      ret i;
  ret -1;
}

static <A> int indexOf(L<A> l, int startIndex, A a) {
  ret indexOf(l, a, startIndex);
}

static <A> int indexOf(L<A> l, A a) {
  if (l == null) ret -1;
  ret l.indexOf(a);
}

static int indexOf(S a, S b) {
  ret a == null || b == null ? -1 : a.indexOf(b);
}

static int indexOf(S a, S b, int i) {
  ret a == null || b == null ? -1 : a.indexOf(b, i);
}

static int indexOf(S a, char b) {
  ret a == null ? -1 : a.indexOf(b);
}

static int indexOf(S a, int i, char b) {
  ret indexOf(a, b, i);
}

static int indexOf(S a, char b, int i) {
  ret a == null ? -1 : a.indexOf(b, i);
}

static int indexOf(S a, int i, S b) {
  ret a == null || b == null ? -1 : a.indexOf(b, i);
}

static <A> int indexOf(A[] x, A a) {
  int n = l(x);
  for (int i = 0; i < n; i++)
    if (eq(x[i], a))
      ret i;
  ret -1;
}

static <A> int indexOf(Iterable<A> l, A a) {
  if (l == null) ret -1;
  int i = 0;
  for (A x : l) {
    if (eq(x, a))
      ret i;
    i++;
  }
  ret -1;
}