feat: completed solutions

exercises/19_smart_pointers/arc1.rs

@@ -23,13 +23,13 @@ fn main() {
     let numbers: Vec<_> = (0..100u32).collect();
 
     // TODO: Define `shared_numbers` by using `Arc`.
-    // let shared_numbers = ???;
+    let shared_numbers = Arc::new(numbers);
 
     let mut join_handles = Vec::new();
 
     for offset in 0..8 {
         // TODO: Define `child_numbers` using `shared_numbers`.
-        // let child_numbers = ???;
+        let child_numbers = Arc::clone(&shared_numbers);
 
         let handle = thread::spawn(move || {
             let sum: u32 = child_numbers.iter().filter(|&&n| n % 8 == offset).sum();

exercises/19_smart_pointers/box1.rs

@@ -12,18 +12,18 @@
 // TODO: Use a `Box` in the enum definition to make the code compile.
 #[derive(PartialEq, Debug)]
 enum List {
-    Cons(i32, List),
+    Cons(i32, Box<List>),
     Nil,
 }
 
 // TODO: Create an empty cons list.
 fn create_empty_list() -> List {
-    todo!()
+    List::Nil
 }
 
 // TODO: Create a non-empty cons list.
 fn create_non_empty_list() -> List {
-    todo!()
+    List::Cons(64, Box::new(List::Nil))
 }
 
 fn main() {

exercises/19_smart_pointers/cow1.rs

@@ -39,7 +39,7 @@ mod tests {
         let mut input = Cow::from(&vec);
         abs_all(&mut input);
         // TODO: Replace `todo!()` with `Cow::Owned(_)` or `Cow::Borrowed(_)`.
-        assert!(matches!(input, todo!()));
+        assert!(matches!(input, Cow::Borrowed(_)));
     }
 
     #[test]
@@ -52,7 +52,7 @@ mod tests {
         let mut input = Cow::from(vec);
         abs_all(&mut input);
         // TODO: Replace `todo!()` with `Cow::Owned(_)` or `Cow::Borrowed(_)`.
-        assert!(matches!(input, todo!()));
+        assert!(matches!(input, Cow::Owned(_)));
     }
 
     #[test]
@@ -64,6 +64,6 @@ mod tests {
         let mut input = Cow::from(vec);
         abs_all(&mut input);
         // TODO: Replace `todo!()` with `Cow::Owned(_)` or `Cow::Borrowed(_)`.
-        assert!(matches!(input, todo!()));
+        assert!(matches!(input, Cow::Owned(_)));
     }
 }

exercises/19_smart_pointers/rc1.rs

@@ -60,17 +60,17 @@ mod tests {
         jupiter.details();
 
         // TODO
-        let saturn = Planet::Saturn(Rc::new(Sun));
+        let saturn = Planet::Saturn(Rc::clone(&sun));
         println!("reference count = {}", Rc::strong_count(&sun)); // 7 references
         saturn.details();
 
         // TODO
-        let uranus = Planet::Uranus(Rc::new(Sun));
+        let uranus = Planet::Uranus(Rc::clone(&sun));
         println!("reference count = {}", Rc::strong_count(&sun)); // 8 references
         uranus.details();
 
         // TODO
-        let neptune = Planet::Neptune(Rc::new(Sun));
+        let neptune = Planet::Neptune(Rc::clone(&sun));
         println!("reference count = {}", Rc::strong_count(&sun)); // 9 references
         neptune.details();
 
@@ -91,13 +91,13 @@ mod tests {
         drop(mars);
         println!("reference count = {}", Rc::strong_count(&sun)); // 4 references
 
-        // TODO
+        drop(earth);
         println!("reference count = {}", Rc::strong_count(&sun)); // 3 references
 
-        // TODO
+        drop(venus);
         println!("reference count = {}", Rc::strong_count(&sun)); // 2 references
 
-        // TODO
+        drop(mercury);
         println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference
 
         assert_eq!(Rc::strong_count(&sun), 1);