public/subjects/moving_targets/README.md

moving_targets

Instructions

You will have a linked list of Target named Field.

You will handle recursive types and ownership and implement the following associated functions:

• new: which will initialize the Field with head set to None.
• push: which receives a Target and add it as a Node at the head of the list.
• pop: which returns the last added Target wrapped in an Option and removes it from the list.
• peek: which returns the last added Target as a reference wrapped in an Option but do not removes it from the list.
• peek_mut: which returns the last added Target as a mutable reference wrapped in an Option and also do not removes it from the list.

You must also implement a type named Link. This will be the connection between the Field and Target structures. This will be a recursion type, and it must point to None if there is no Target to point to.

Expected Functions and structures

pub struct Field {
    head: Link,
}

type Link = // To be implemented

struct Node {
    elem: Target,
    next: Link,
}

#[derive(Debug, PartialEq, Eq)]
pub struct Target {
    pub size: u32,
    pub xp: u32,
}
impl Field {
    pub fn new() -> Self {}
    pub fn push(&mut self, target: Target) {}
    pub fn pop(&mut self) -> Option<Target> {}
    pub fn peek(&self) -> Option<&Target> {}
    pub fn peek_mut(&mut self) -> Option<&mut Target> {}
}

Usage

Here is a program to test your function:

use moving_targets::*;

fn main() {
    let mut field = Field::new();

    println!("{:?}", field.pop());
    field.push(Target { size: 12, xp: 2 });
    println!("{:?}", *field.peek().unwrap());
    field.push(Target { size: 24, xp: 4 });
    println!("{:?}", field.pop());
    let last_target = field.peek_mut().unwrap();
    *last_target = Target { size: 2, xp: 0 };
    println!("{:?}", field.pop());
}

And its output:

$ cargo run
None
Target { size: 12, xp: 2 }
Some(Target { size: 24, xp: 4 })
Some(Target { size: 2, xp: 0 })
$

Notions

• Box<T>
• Linked lists in Rust