Beauty of Rust

lifetimes.rs

#![allow(dead_code, unused_variables)]

#[derive(Debug)]
struct Node<'l, 'r> {
    val: u32,
    left: Option<&'l Node<'l, 'l>>,
    right: Option<&'r Node<'r, 'r>>
}

impl<'l, 'r> Node<'l, 'r> {
    fn leaf(val: u32) -> Node<'l, 'r> {
        Node { val: val, left: None, right: None }
    }
    fn new(val: u32, left: &'l Node<'l, 'l>, right: &'r Node<'r, 'r>) -> Node<'l, 'r> {
        Node { val: val, left: Some(left), right: Some(right) }
    }
}

enum Dir {
    Left, Right
}

struct Choice {
    choice: Dir
}

fn choose<'n>(node: &'n Node<'n, 'n>, what: &Choice) -> Option<&'n Node<'n, 'n>> {
    match what.choice {
        Dir::Left  => node.left,
        Dir::Right => node.right
    }
}

fn main() {
    let left = Node::leaf(1);
    let right = Node::leaf(2);
    let root = Node::new(3, &left, &right);

    let result = choose(&root, &Choice { choice: Dir::Right });

    println!("\nresult: {:?}", result);
}