box.rs

    #[deriving(Show)]
    struct Monster {
        name: String,
        hp: uint
    }

    struct Game {
        monsters: Vec<Box<Monster>>
    }

    impl Game {
        pub fn new() -> Game {
            Game { monsters: vec![] }
        }

        pub fn add_monster(&mut self, monster: Monster) {
            self.monsters.push(box monster)
        }

    pub fn fight(&mut self) {
        let (left, right) = self.monsters.split_at_mut(1);
        let m1 = &mut left[0];
        let m2 = &right[0];

        m1.hp = 9;
    }

        pub fn foo2(&mut self) {
            let (idx, dmg ) = {
                let m2 = &self.monsters[1];
                let m1 = &self.monsters[0];
                (0u, 9u)
            };
            self.monsters[idx].hp -= dmg;
        }
    }

    #[test]
    fn test_monsters() {
        let mut foo = Game::new();

        foo.add_monster(Monster { name: "Guss".to_string(), hp: 10 });
        foo.add_monster(Monster { name: "Biff".to_string(), hp: 10 });
        foo.fight();
        panic!("monster {}", foo.monsters[0]);
    }