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use elsa::FrozenVec;
fn main() {
let arena = Arena::new();
let lonely = arena.add_thing("lonely", vec![]);
let best_friend = arena.add_thing("best friend", vec![lonely]);
let threes_a_crowd = arena.add_thing("threes a crowd", vec![lonely, best_friend]);
let rando = arena.add_thing("rando", vec![]);
let _facebook = arena.add_thing("facebook", vec![rando, threes_a_crowd, lonely, best_friend]);
assert!(cmp_ref(lonely, best_friend.friends[0]));
assert!(cmp_ref(best_friend, threes_a_crowd.friends[1]));
arena.dump();
}
struct Arena<'arena> {
things: FrozenVec<Box<Thing<'arena>>>,
}
struct Thing<'arena> {
pub friends: Vec<ThingRef<'arena>>,
pub name: &'static str,
}
type ThingRef<'arena> = &'arena Thing<'arena>;
impl<'arena> Arena<'arena> {
fn new() -> Arena<'arena> {
Arena {
things: FrozenVec::new(),
}
}
fn add_thing(
&'arena self,
name: &'static str,
friends: Vec<ThingRef<'arena>>,
) -> ThingRef<'arena> {
let idx = self.things.len();
self.things.push(Box::new(Thing { name, friends }));
&self.things[idx]
}
fn dump(&'arena self) {
for thing in &self.things {
println!("friends of {}:", thing.name);
for friend in &thing.friends {
println!("\t{}", friend.name);
}
}
}
}
fn cmp_ref<T>(x: &T, y: &T) -> bool {
x as *const T as usize == y as *const T as usize
}
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