Array#intersect?

static VALUE
rb_ary_intersect_p(VALUE ary1, VALUE ary2)
{
    ary2 = to_ary(ary2);
    if (RARRAY_LEN(ary1) == 0 || RARRAY_LEN(ary2) == 0) return Qfalse;

    if (RARRAY_LEN(ary1) <= SMALL_ARRAY_LEN && RARRAY_LEN(ary2) <= SMALL_ARRAY_LEN) {
        for (rb_len_t i = 0; i < RARRAY_LEN(ary1); i++) {
            VALUE v = RARRAY_AREF(ary1, i);
            if (rb_ary_includes_by_eql(ary2, v)) return Qtrue;
        }
        return Qfalse;
    }

    VALUE shorter = ary1;
    VALUE longer = ary2;
    if (RARRAY_LEN(ary1) > RARRAY_LEN(ary2)) {
        longer = ary1;
        shorter = ary2;
    }

    VALUE set = ary_to_set(shorter);
    VALUE result = Qfalse;

    for (rb_len_t i = 0; i < RARRAY_LEN(longer); i++) {
        VALUE v = RARRAY_AREF(longer, i);
        if (rb_set_lookup(set, v)) {
            result = Qtrue;
            break;
        }
    }

    return result;
}