1 files changed, 56 insertions, 0 deletions
diff --git a/vendor/elsa/examples/arena.rs b/vendor/elsa/examples/arena.rs
new file mode 100644
index 000000000..79913c2e7
--- /dev/null
+++ b/vendor/elsa/examples/arena.rs
@@ -0,0 +1,56 @@
+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
+}