src/doc/book/listings/ch15-smart-pointers/listing-15-19/src/main.rs

   1 enum List {
   2     Cons(i32, Rc<List>),
   3     Nil,
   4 }
   5
   6 use crate::List::{Cons, Nil};
   7 use std::rc::Rc;
   8
   9 // ANCHOR: here
  10 fn main() {
  11     let a = Rc::new(Cons(5, Rc::new(Cons(10, Rc::new(Nil)))));
  12     println!("count after creating a = {}", Rc::strong_count(&a));
  13     let b = Cons(3, Rc::clone(&a));
  14     println!("count after creating b = {}", Rc::strong_count(&a));
  15     {
  16         let c = Cons(4, Rc::clone(&a));
  17         println!("count after creating c = {}", Rc::strong_count(&a));
  18     }
  19     println!("count after c goes out of scope = {}", Rc::strong_count(&a));
  20 }
  21 // ANCHOR_END: here