rc.rs

enum List {
    Cons(i32, Rc<List>),
    Nil,
}
 
use crate::List::{Cons, Nil};
use std::rc::Rc;
 
fn main() {
    let a = Rc::new(Cons(5, Rc::new(Cons(10, Rc::new(Nil)))));
    println!("count after creating a = {}", Rc::strong_count(&a));
    let _b = Cons(3, Rc::clone(&a));
    println!("count after creating b = {}", Rc::strong_count(&a));
    {
        let _c = Cons(4, Rc::clone(&a));
        println!("count after creating c = {}", Rc::strong_count(&a));
    }
 
    println!("count after creating c goes out of scope = {}", Rc::strong_count(&a));
}