First quiz and its related modules

exercises/smart_pointers/arc1.rs

@@ -32,7 +32,7 @@ fn main() {
     for offset in 0..8 {
         let child_numbers = // TODO
         joinhandles.push(thread::spawn(move || {
-            let sum: u32 = child_numbers.iter().filter(|&&n| n % 8 == offset).sum();
+            let sum: u32 = child_numbers.iter().filter(|n| *n % 8 == offset).sum();
             println!("Sum of offset {} is {}", offset, sum);
         }));
     }

exercises/smart_pointers/cow1.rs

@@ -4,9 +4,6 @@
 // Cow is a clone-on-write smart pointer.
 // It can enclose and provide immutable access to borrowed data, and clone the data lazily when mutation or ownership is required.
 // The type is designed to work with general borrowed data via the Borrow trait.
-//
-// This exercise is meant to show you what to expect when passing data to Cow.
-// Fix the unit tests by checking for Cow::Owned(_) and Cow::Borrowed(_) at the TODO markers.
 
 // I AM NOT DONE
 
@@ -23,52 +20,29 @@ fn abs_all<'a, 'b>(input: &'a mut Cow<'b, [i32]>) -> &'a mut Cow<'b, [i32]> {
     input
 }
 
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn reference_mutation() -> Result<(), &'static str> {
-        // Clone occurs because `input` needs to be mutated.
-        let slice = [-1, 0, 1];
-        let mut input = Cow::from(&slice[..]);
-        match abs_all(&mut input) {
-            Cow::Owned(_) => Ok(()),
-            _ => Err("Expected owned value"),
-        }
+fn main() {
+    // No clone occurs because `input` doesn't need to be mutated.
+    let slice = [0, 1, 2];
+    let mut input = Cow::from(&slice[..]);
+    match abs_all(&mut input) {
+        Cow::Borrowed(_) => println!("I borrowed the slice!"),
+        _ => panic!("expected borrowed value"),
     }
 
-    #[test]
-    fn reference_no_mutation() -> Result<(), &'static str> {
-        // No clone occurs because `input` doesn't need to be mutated.
-        let slice = [0, 1, 2];
-        let mut input = Cow::from(&slice[..]);
-        match abs_all(&mut input) {
-            // TODO
-        }
+    // Clone occurs because `input` needs to be mutated.
+    let slice = [-1, 0, 1];
+    let mut input = Cow::from(&slice[..]);
+    match abs_all(&mut input) {
+        Cow::Owned(_) => println!("I modified the slice and now own it!"),
+        _ => panic!("expected owned value"),
     }
 
-    #[test]
-    fn owned_no_mutation() -> Result<(), &'static str> {
-        // We can also pass `slice` without `&` so Cow owns it directly.
-        // In this case no mutation occurs and thus also no clone,
-        // but the result is still owned because it always was.
-        let slice = vec![0, 1, 2];
-        let mut input = Cow::from(slice);
-        match abs_all(&mut input) {
-            // TODO
-        }
-    }
-
-    #[test]
-    fn owned_mutation() -> Result<(), &'static str> {
-        // Of course this is also the case if a mutation does occur.
-        // In this case the call to `to_mut()` returns a reference to
-        // the same data as before.
-        let slice = vec![-1, 0, 1];
-        let mut input = Cow::from(slice);
-        match abs_all(&mut input) {
-            // TODO
-        }
+    // No clone occurs because `input` is already owned.
+    let slice = vec![-1, 0, 1];
+    let mut input = Cow::from(slice);
+    match abs_all(&mut input) {
+        // TODO
+        Cow::Borrowed(_) => println!("I own this slice!"),
+        _ => panic!("expected borrowed value"),
     }
 }