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use elsa::FrozenVec;
fn main() {
let arena = Arena::new();
let lonely = arena.add_person("lonely", vec![]);
let best_friend = arena.add_person("best friend", vec![lonely]);
let threes_a_crowd = arena.add_person("threes a crowd", vec![lonely, best_friend]);
let rando = arena.add_person("rando", vec![]);
let _everyone = arena.add_person(
"follows everyone",
vec![rando, threes_a_crowd, lonely, best_friend],
);
arena.dump();
}
struct Arena<'arena> {
people: FrozenVec<Box<Person<'arena>>>,
}
struct Person<'arena> {
pub follows: FrozenVec<PersonRef<'arena>>,
pub reverse_follows: FrozenVec<PersonRef<'arena>>,
pub name: &'static str,
}
type PersonRef<'arena> = &'arena Person<'arena>;
impl<'arena> Arena<'arena> {
fn new() -> Arena<'arena> {
Arena {
people: FrozenVec::new(),
}
}
fn add_person(
&'arena self,
name: &'static str,
follows: Vec<PersonRef<'arena>>,
) -> PersonRef<'arena> {
let idx = self.people.len();
self.people.push(Box::new(Person {
name,
follows: follows.into(),
reverse_follows: Default::default(),
}));
let me = &self.people[idx];
for friend in &me.follows {
friend.reverse_follows.push(me)
}
me
}
fn dump(&'arena self) {
for thing in &self.people {
println!("{} network:", thing.name);
println!("\tfollowing:");
for friend in &thing.follows {
println!("\t\t{}", friend.name);
}
println!("\tfollowers:");
for friend in &thing.reverse_follows {
println!("\t\t{}", friend.name);
}
}
}
}
// Note that the following will cause the above code to stop compiling
// since non-eyepatched custom destructors can potentially
// read deallocated data.
//
// impl<'arena> Drop for Person<'arena> {
// fn drop(&mut self) {
// println!("goodbye {:?}", self.name);
// for friend in &self.follows {
// println!("\t\t{}", friend.name);
// }
// }
// }
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