// Rc and RefCell
// https://cs.hofstra.edu/~cscccl/csc123/rust/memleak.rs

use std::cell::RefCell;
use std::rc::Rc;

fn main() {
/*
   let rc:Rc<RefCell<i32>> = Rc::new(RefCell::new(5));
   *rc.borrow_mut() += 1;
*/
/*
   let mut rc:Rc<i32> = Rc::new(5);
    *rc += 1;


   let mut rc:Box<i32> = Box::new(5);
    *rc += 1;
*/

   let rc:Rc<RefCell<i32>> = Rc::new(RefCell::new(5));
   let borrow = rc.borrow();
   *rc.borrow_mut() += 1;
   println!(" value inside the cell: {}", &borrow); 

/*
   let rc:Rc<RefCell<i32>> = Rc::new(RefCell::new(5));
   let rc2 = rc.clone(); // rc2 and rc shares the refcell
   *rc.borrow_mut() += 1;
   println!("value inside the cell: {}", rc2.borrow());
*/

//while true {leak();}
}//main

struct Node {
  item : Vec<i32>,
  next : Option<Rc<RefCell<Node>>>, 
}

fn leak() {
  let mut a = Node { item:vec![1,2,3], next: None };
  let mut b = Node { item:vec![4,5,6], next: None };
  let rca = Rc::new(RefCell::new(a));
  let rcb = Rc::new(RefCell::new(b));
  
  rca.borrow_mut().next = Some(rcb.clone());
  rcb.borrow_mut().next = Some(rca.clone());
  // this creates a cycle and a memory leak
}