struct Mylist {
  v: i32,
  next: Option<std::rc::Rc<Mylist>>
}

impl Mylist {
  fn new(val: i32) -> std::rc::Rc<Mylist>
  {
    std::rc::Rc::new(Mylist{v: val, next: None}) 
  }

  fn append(val: i32, l: std::rc::Rc<Mylist>) -> std::rc::Rc<Mylist>
  {
    std::rc::Rc::new(Mylist{v: val, next: Some(l)})
  }
}

impl Drop for Mylist {
  fn drop(&mut self)
  {
    println!("Node with value {} is being destroyed!", self.v) 
  }
}

fn main()
{
  let l1 = Mylist::new(5);
  let l2 = Mylist::append(6, l1.clone());

  {
    let l3 = Mylist::append(7, l2.clone());

    println!("l3: {}", l3.v);
  }
  println!("l2: {}", l2.v);

  if let Some(next) = l2.next.clone() {
    println!("l2->next: {}", next.v);
  } else {
    println!("l2->next is empty!");
  }
}