Merge remote-tracking branch 'upstream/main' into fix-enum-variant-inconsistency

4 files changed, 150 insertions, 167 deletions

diff --git a/exercises/19_smart_pointers/arc1.rs b/exercises/19_smart_pointers/arc1.rs
index 3526ddc..6bb860f 100644
--- a/exercises/19_smart_pointers/arc1.rs
+++ b/exercises/19_smart_pointers/arc1.rs
@@ -1,45 +1,45 @@
-// arc1.rs
+// In this exercise, we are given a `Vec` of `u32` called `numbers` with values
+// ranging from 0 to 99. We would like to use this set of numbers within 8
+// different threads simultaneously. Each thread is going to get the sum of
+// every eighth value with an offset.
 //
-// In this exercise, we are given a Vec of u32 called "numbers" with values
-// ranging from 0 to 99 -- [ 0, 1, 2, ..., 98, 99 ] We would like to use this
-// set of numbers within 8 different threads simultaneously. Each thread is
-// going to get the sum of every eighth value, with an offset.
+// The first thread (offset 0), will sum 0, 8, 16, …
+// The second thread (offset 1), will sum 1, 9, 17, …
+// The third thread (offset 2), will sum 2, 10, 18, …
+// …
+// The eighth thread (offset 7), will sum 7, 15, 23, …
 //
-// The first thread (offset 0), will sum 0, 8, 16, ...
-// The second thread (offset 1), will sum 1, 9, 17, ...
-// The third thread (offset 2), will sum 2, 10, 18, ...
-// ...
-// The eighth thread (offset 7), will sum 7, 15, 23, ...
+// Each thread should own a reference-counting pointer to the vector of
+// numbers. But `Rc` isn't thread-safe. Therefore, we need to use `Arc`.
 //
-// Because we are using threads, our values need to be thread-safe.  Therefore,
-// we are using Arc.  We need to make a change in each of the two TODOs.
-//
-// Make this code compile by filling in a value for `shared_numbers` where the
-// first TODO comment is, and create an initial binding for `child_numbers`
-// where the second TODO comment is. Try not to create any copies of the
-// `numbers` Vec!
-//
-// Execute `rustlings hint arc1` or use the `hint` watch subcommand for a hint.
+// Don't get distracted by how threads are spawned and joined. We will practice
+// that later in the exercises about threads.
 
-// I AM NOT DONE
-
-#![forbid(unused_imports)] // Do not change this, (or the next) line.
-use std::sync::Arc;
-use std::thread;
+// Don't change the lines below.
+#![forbid(unused_imports)]
+use std::{sync::Arc, thread};
 
 fn main() {
     let numbers: Vec<_> = (0..100u32).collect();
-    let shared_numbers = // TODO
-    let mut joinhandles = Vec::new();
+
+    // TODO: Define `shared_numbers` by using `Arc`.
+    // let shared_numbers = ???;
+
+    let mut join_handles = Vec::new();
 
     for offset in 0..8 {
-        let child_numbers = // TODO
-        joinhandles.push(thread::spawn(move || {
+        // TODO: Define `child_numbers` using `shared_numbers`.
+        // let child_numbers = ???;
+
+        let handle = thread::spawn(move || {
             let sum: u32 = child_numbers.iter().filter(|&&n| n % 8 == offset).sum();
-            println!("Sum of offset {} is {}", offset, sum);
-        }));
+            println!("Sum of offset {offset} is {sum}");
+        });
+
+        join_handles.push(handle);
     }
-    for handle in joinhandles.into_iter() {
+
+    for handle in join_handles.into_iter() {
         handle.join().unwrap();
     }
 }
diff --git a/exercises/19_smart_pointers/box1.rs b/exercises/19_smart_pointers/box1.rs
index 513e7da..d70e1c3 100644
--- a/exercises/19_smart_pointers/box1.rs
+++ b/exercises/19_smart_pointers/box1.rs
@@ -1,45 +1,37 @@
-// box1.rs
-//
 // At compile time, Rust needs to know how much space a type takes up. This
 // becomes problematic for recursive types, where a value can have as part of
 // itself another value of the same type. To get around the issue, we can use a
 // `Box` - a smart pointer used to store data on the heap, which also allows us
 // to wrap a recursive type.
 //
-// The recursive type we're implementing in this exercise is the `cons list` - a
+// The recursive type we're implementing in this exercise is the "cons list", a
 // data structure frequently found in functional programming languages. Each
-// item in a cons list contains two elements: the value of the current item and
+// item in a cons list contains two elements: The value of the current item and
 // the next item. The last item is a value called `Nil`.
-//
-// Step 1: use a `Box` in the enum definition to make the code compile
-// Step 2: create both empty and non-empty cons lists by replacing `todo!()`
-//
-// Note: the tests should not be changed
-//
-// Execute `rustlings hint box1` or use the `hint` watch subcommand for a hint.
-
-// I AM NOT DONE
 
+// TODO: Use a `Box` in the enum definition to make the code compile.
 #[derive(PartialEq, Debug)]
-pub enum List {
+enum List {
     Cons(i32, List),
     Nil,
 }
 
-fn main() {
-    println!("This is an empty cons list: {:?}", create_empty_list());
-    println!(
-        "This is a non-empty cons list: {:?}",
-        create_non_empty_list()
-    );
+// TODO: Create an empty cons list.
+fn create_empty_list() -> List {
+    todo!()
 }
 
-pub fn create_empty_list() -> List {
+// TODO: Create a non-empty cons list.
+fn create_non_empty_list() -> List {
     todo!()
 }
 
-pub fn create_non_empty_list() -> List {
-    todo!()
+fn main() {
+    println!("This is an empty cons list: {:?}", create_empty_list());
+    println!(
+        "This is a non-empty cons list: {:?}",
+        create_non_empty_list(),
+    );
 }
 
 #[cfg(test)]
@@ -48,11 +40,11 @@ mod tests {
 
     #[test]
     fn test_create_empty_list() {
-        assert_eq!(List::Nil, create_empty_list())
+        assert_eq!(create_empty_list(), List::Nil);
     }
 
     #[test]
     fn test_create_non_empty_list() {
-        assert_ne!(create_empty_list(), create_non_empty_list())
+        assert_ne!(create_empty_list(), create_non_empty_list());
     }
 }
diff --git a/exercises/19_smart_pointers/cow1.rs b/exercises/19_smart_pointers/cow1.rs
index fcd3e0b..5ecf848 100644
--- a/exercises/19_smart_pointers/cow1.rs
+++ b/exercises/19_smart_pointers/cow1.rs
@@ -1,30 +1,22 @@
-// cow1.rs
-//
-// This exercise explores the Cow, or Clone-On-Write type. 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.
-//
-// Execute `rustlings hint cow1` or use the `hint` watch subcommand for a hint.
-
-// I AM NOT DONE
+// This exercise explores the `Cow` (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.
 
 use std::borrow::Cow;
 
-fn abs_all<'a, 'b>(input: &'a mut Cow<'b, [i32]>) -> &'a mut Cow<'b, [i32]> {
-    for i in 0..input.len() {
-        let v = input[i];
-        if v < 0 {
+fn abs_all(input: &mut Cow<[i32]>) {
+    for ind in 0..input.len() {
+        let value = input[ind];
+        if value < 0 {
             // Clones into a vector if not already owned.
-            input.to_mut()[i] = -v;
+            input.to_mut()[ind] = -value;
         }
     }
-    input
+}
+
+fn main() {
+    // You can optionally experiment here.
 }
 
 #[cfg(test)]
@@ -32,47 +24,45 @@ mod tests {
     use super::*;
 
     #[test]
-    fn reference_mutation() -> Result<(), &'static str> {
+    fn reference_mutation() {
         // 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"),
-        }
+        let vec = vec![-1, 0, 1];
+        let mut input = Cow::from(&vec);
+        abs_all(&mut input);
+        assert!(matches!(input, Cow::Owned(_)));
     }
 
     #[test]
-    fn reference_no_mutation() -> Result<(), &'static str> {
+    fn reference_no_mutation() {
         // 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
-        }
+        let vec = vec![0, 1, 2];
+        let mut input = Cow::from(&vec);
+        abs_all(&mut input);
+        // TODO: Replace `todo!()` with `Cow::Owned(_)` or `Cow::Borrowed(_)`.
+        assert!(matches!(input, todo!()));
     }
 
     #[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
+    fn owned_no_mutation() {
+        // We can also pass `vec` 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 was never borrowed or mutated.
-        let slice = vec![0, 1, 2];
-        let mut input = Cow::from(slice);
-        match abs_all(&mut input) {
-            // TODO
-        }
+        let vec = vec![0, 1, 2];
+        let mut input = Cow::from(vec);
+        abs_all(&mut input);
+        // TODO: Replace `todo!()` with `Cow::Owned(_)` or `Cow::Borrowed(_)`.
+        assert!(matches!(input, todo!()));
     }
 
     #[test]
-    fn owned_mutation() -> Result<(), &'static str> {
+    fn owned_mutation() {
         // Of course this is also the case if a mutation does occur. In this
-        // case the call to `to_mut()` in the abs_all() function returns a
+        // case, the call to `to_mut()` in the `abs_all` function 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
-        }
+        let vec = vec![-1, 0, 1];
+        let mut input = Cow::from(vec);
+        abs_all(&mut input);
+        // TODO: Replace `todo!()` with `Cow::Owned(_)` or `Cow::Borrowed(_)`.
+        assert!(matches!(input, todo!()));
     }
 }
diff --git a/exercises/19_smart_pointers/rc1.rs b/exercises/19_smart_pointers/rc1.rs
index 1b90346..48e19dc 100644
--- a/exercises/19_smart_pointers/rc1.rs
+++ b/exercises/19_smart_pointers/rc1.rs
@@ -1,22 +1,14 @@
-// rc1.rs
-//
 // In this exercise, we want to express the concept of multiple owners via the
-// Rc<T> type. This is a model of our solar system - there is a Sun type and
-// multiple Planets. The Planets take ownership of the sun, indicating that they
-// revolve around the sun.
-//
-// Make this code compile by using the proper Rc primitives to express that the
-// sun has multiple owners.
-//
-// Execute `rustlings hint rc1` or use the `hint` watch subcommand for a hint.
-
-// I AM NOT DONE
+// `Rc<T>` type. This is a model of our solar system - there is a `Sun` type and
+// multiple `Planet`s. The planets take ownership of the sun, indicating that
+// they revolve around the sun.
 
 use std::rc::Rc;
 
 #[derive(Debug)]
-struct Sun {}
+struct Sun;
 
+#[allow(dead_code)]
 #[derive(Debug)]
 enum Planet {
     Mercury(Rc<Sun>),
@@ -31,75 +23,84 @@ enum Planet {
 
 impl Planet {
     fn details(&self) {
-        println!("Hi from {:?}!", self)
+        println!("Hi from {self:?}!");
     }
 }
 
-#[test]
 fn main() {
-    let sun = Rc::new(Sun {});
-    println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
 
-    let mercury = Planet::Mercury(Rc::clone(&sun));
-    println!("reference count = {}", Rc::strong_count(&sun)); // 2 references
-    mercury.details();
+    #[test]
+    fn rc1() {
+        let sun = Rc::new(Sun);
+        println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference
 
-    let venus = Planet::Venus(Rc::clone(&sun));
-    println!("reference count = {}", Rc::strong_count(&sun)); // 3 references
-    venus.details();
+        let mercury = Planet::Mercury(Rc::clone(&sun));
+        println!("reference count = {}", Rc::strong_count(&sun)); // 2 references
+        mercury.details();
 
-    let earth = Planet::Earth(Rc::clone(&sun));
-    println!("reference count = {}", Rc::strong_count(&sun)); // 4 references
-    earth.details();
+        let venus = Planet::Venus(Rc::clone(&sun));
+        println!("reference count = {}", Rc::strong_count(&sun)); // 3 references
+        venus.details();
 
-    let mars = Planet::Mars(Rc::clone(&sun));
-    println!("reference count = {}", Rc::strong_count(&sun)); // 5 references
-    mars.details();
+        let earth = Planet::Earth(Rc::clone(&sun));
+        println!("reference count = {}", Rc::strong_count(&sun)); // 4 references
+        earth.details();
 
-    let jupiter = Planet::Jupiter(Rc::clone(&sun));
-    println!("reference count = {}", Rc::strong_count(&sun)); // 6 references
-    jupiter.details();
+        let mars = Planet::Mars(Rc::clone(&sun));
+        println!("reference count = {}", Rc::strong_count(&sun)); // 5 references
+        mars.details();
 
-    // TODO
-    let saturn = Planet::Saturn(Rc::new(Sun {}));
-    println!("reference count = {}", Rc::strong_count(&sun)); // 7 references
-    saturn.details();
+        let jupiter = Planet::Jupiter(Rc::clone(&sun));
+        println!("reference count = {}", Rc::strong_count(&sun)); // 6 references
+        jupiter.details();
 
-    // TODO
-    let uranus = Planet::Uranus(Rc::new(Sun {}));
-    println!("reference count = {}", Rc::strong_count(&sun)); // 8 references
-    uranus.details();
+        // TODO
+        let saturn = Planet::Saturn(Rc::new(Sun));
+        println!("reference count = {}", Rc::strong_count(&sun)); // 7 references
+        saturn.details();
 
-    // TODO
-    let neptune = Planet::Neptune(Rc::new(Sun {}));
-    println!("reference count = {}", Rc::strong_count(&sun)); // 9 references
-    neptune.details();
+        // TODO
+        let uranus = Planet::Uranus(Rc::new(Sun));
+        println!("reference count = {}", Rc::strong_count(&sun)); // 8 references
+        uranus.details();
 
-    assert_eq!(Rc::strong_count(&sun), 9);
+        // TODO
+        let neptune = Planet::Neptune(Rc::new(Sun));
+        println!("reference count = {}", Rc::strong_count(&sun)); // 9 references
+        neptune.details();
 
-    drop(neptune);
-    println!("reference count = {}", Rc::strong_count(&sun)); // 8 references
+        assert_eq!(Rc::strong_count(&sun), 9);
 
-    drop(uranus);
-    println!("reference count = {}", Rc::strong_count(&sun)); // 7 references
+        drop(neptune);
+        println!("reference count = {}", Rc::strong_count(&sun)); // 8 references
 
-    drop(saturn);
-    println!("reference count = {}", Rc::strong_count(&sun)); // 6 references
+        drop(uranus);
+        println!("reference count = {}", Rc::strong_count(&sun)); // 7 references
 
-    drop(jupiter);
-    println!("reference count = {}", Rc::strong_count(&sun)); // 5 references
+        drop(saturn);
+        println!("reference count = {}", Rc::strong_count(&sun)); // 6 references
 
-    drop(mars);
-    println!("reference count = {}", Rc::strong_count(&sun)); // 4 references
+        drop(jupiter);
+        println!("reference count = {}", Rc::strong_count(&sun)); // 5 references
 
-    // TODO
-    println!("reference count = {}", Rc::strong_count(&sun)); // 3 references
+        drop(mars);
+        println!("reference count = {}", Rc::strong_count(&sun)); // 4 references
 
-    // TODO
-    println!("reference count = {}", Rc::strong_count(&sun)); // 2 references
+        // TODO
+        println!("reference count = {}", Rc::strong_count(&sun)); // 3 references
 
-    // TODO
-    println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference
+        // TODO
+        println!("reference count = {}", Rc::strong_count(&sun)); // 2 references
 
-    assert_eq!(Rc::strong_count(&sun), 1);
+        // TODO
+        println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference
+
+        assert_eq!(Rc::strong_count(&sun), 1);
+    }
 }