Learning smart pointer,can I use regular references on recursive type?

help
1

I am reading the rust book, it use a "Recursive Type with a Known Size" to introduce Box pointer, But I wonder if I can use a regular reference to build this type?

enum List<'a> {
    Cons(i32, &'a List<'a>),
    Nil,
}

use self::List::Cons;

fn main() {
    let _list = Cons(1,
        &List::Cons(2,
            &List::Nil
        ));
}

Is this valid and meaningful? Is there any problem in it?
Thanks.
The relative section: Box<T> Points to Data on the Heap and Has a Known Size - The Rust Programming Language

2

Yes you can, but you should probably use mutable references so that you can change the list later, and to make it immutable, you can just pass a normal shared reference to the list.
Also, look into Learning Rust With Entirely Too Many Linked Lists, its a good read and it teaches a lot of how Rust works.

3

Thanks, Yeah I should use mutable references, and I did not learn shared reference, now I am not sure what is the advantage of box beyond the regular reference in this example. Thanks for your resources, so much need to learn.

4

Box would be an alternative to mutable pointers if you can't or don't want to mansge the lifetimes of all the sub-lists, or if you need an item to live longer than the current function call. That is the main usecase of Box.