public/subjects/how_many_references

how many references

Instructions

Create the following functions :

• add_ele which adds an element to the value in the Node
• how_many_references which returns how many times the value is referenced in the code
• rm_all_ref which receives a Rc<String> and removes all elements from the vector that are equal to that value, this should only happen if the two Rcs point to the same allocation

Notions

• Reference Counted Smart Pointer
• Struct std::rc::Rc

Expected Functions and structures

pub use std::rc::Rc;

pub struct Node {
    pub value: Vec<Rc<String>>,
}

impl Node {
    pub fn new(value: Vec<Rc<String>>) -> Node {
        Node { value: value }
    }
    pub fn add_ele(&mut self, v: Rc<String>) {}
    pub fn rm_all_ref(&mut self, v: Rc<String>) {}
}

pub fn how_many_references(value: &Rc<String>) -> usize {}

Usage

Here is a program to test your functions,

use how_many_references::*;

fn main() {
    let a = Rc::new(String::from("a"));
    let b = Rc::new(String::from("b"));
    let c = Rc::new(String::from("c"));

    let a1 = Rc::new(String::from("a"));

    let mut new_node = Node::new(vec![a.clone()]);
    new_node.add_ele(b.clone());
    new_node.add_ele(a.clone());
    new_node.add_ele(c.clone());
    new_node.add_ele(a.clone());

    println!("a: {:?}", how_many_references(&a));
    println!("b: {:?}", how_many_references(&b));
    println!("c: {:?}", how_many_references(&c));
    new_node.rm_all_ref(a1.clone());
    new_node.rm_all_ref(a.clone());

    println!("a: {:?}", how_many_references(&a));
    println!("b: {:?}", how_many_references(&b));
    println!("c: {:?}", how_many_references(&c));
}

And its output:

student@ubuntu:~/how_many_references/test$ cargo run
a: 4
b: 2
c: 2
a: 1
b: 2
c: 2
student@ubuntu:~/how_many_references/test$