arena/
arena.rs

1use elsa::FrozenVec;
2
3fn main() {
4    let arena = Arena::new();
5    let lonely = arena.add_thing("lonely", vec![]);
6    let best_friend = arena.add_thing("best friend", vec![lonely]);
7    let threes_a_crowd = arena.add_thing("threes a crowd", vec![lonely, best_friend]);
8    let rando = arena.add_thing("rando", vec![]);
9    let _facebook = arena.add_thing("facebook", vec![rando, threes_a_crowd, lonely, best_friend]);
10
11    assert!(cmp_ref(lonely, best_friend.friends[0]));
12    assert!(cmp_ref(best_friend, threes_a_crowd.friends[1]));
13    arena.dump();
14}
15
16struct Arena<'arena> {
17    things: FrozenVec<Box<Thing<'arena>>>,
18}
19
20struct Thing<'arena> {
21    pub friends: Vec<ThingRef<'arena>>,
22    pub name: &'static str,
23}
24
25type ThingRef<'arena> = &'arena Thing<'arena>;
26
27impl<'arena> Arena<'arena> {
28    fn new() -> Arena<'arena> {
29        Arena {
30            things: FrozenVec::new(),
31        }
32    }
33
34    fn add_thing(
35        &'arena self,
36        name: &'static str,
37        friends: Vec<ThingRef<'arena>>,
38    ) -> ThingRef<'arena> {
39        let idx = self.things.len();
40        self.things.push(Box::new(Thing { name, friends }));
41        &self.things[idx]
42    }
43
44    fn dump(&'arena self) {
45        for thing in &self.things {
46            println!("friends of {}:", thing.name);
47            for friend in &thing.friends {
48                println!("\t{}", friend.name);
49            }
50        }
51    }
52}
53
54fn cmp_ref<T>(x: &T, y: &T) -> bool {
55    std::ptr::eq(x, y)
56}
arena/arena.rs

arena/
arena.rs
