clippy3 solution

exercises/20_threads/threads1.rs

@@ -3,31 +3,35 @@
 // wait until all the spawned threads have finished and should collect their
 // return values into a vector.
 
-use std::thread;
-use std::time::{Duration, Instant};
+use std::{
+    thread,
+    time::{Duration, Instant},
+};
 
 fn main() {
-    let mut handles = vec![];
+    let mut handles = Vec::new();
     for i in 0..10 {
-        handles.push(thread::spawn(move || {
+        let handle = thread::spawn(move || {
             let start = Instant::now();
             thread::sleep(Duration::from_millis(250));
-            println!("thread {} is complete", i);
+            println!("Thread {i} done");
             start.elapsed().as_millis()
-        }));
+        });
+        handles.push(handle);
     }
 
-    let mut results: Vec<u128> = vec![];
+    let mut results = Vec::new();
     for handle in handles {
-        // TODO: a struct is returned from thread::spawn, can you use it?
+        // TODO: Collect the results of all threads into the `results` vector.
+        // Use the `JoinHandle` struct which is returned by `thread::spawn`.
     }
 
     if results.len() != 10 {
-        panic!("Oh no! All the spawned threads did not finish!");
+        panic!("Oh no! Some thread isn't done yet!");
     }
 
     println!();
     for (i, result) in results.into_iter().enumerate() {
-        println!("thread {} took {}ms", i, result);
+        println!("Thread {i} took {result}ms");
     }
 }

exercises/20_threads/threads2.rs

@@ -1,35 +1,34 @@
 // Building on the last exercise, we want all of the threads to complete their
-// work but this time the spawned threads need to be in charge of updating a
-// shared value: JobStatus.jobs_completed
+// work. But this time, the spawned threads need to be in charge of updating a
+// shared value: `JobStatus.jobs_done`
 
-use std::sync::Arc;
-use std::thread;
-use std::time::Duration;
+use std::{sync::Arc, thread, time::Duration};
 
 struct JobStatus {
-    jobs_completed: u32,
+    jobs_done: u32,
 }
 
 fn main() {
-    // TODO: `Arc` isn't enough if you want a **mutable** shared state
-    let status = Arc::new(JobStatus { jobs_completed: 0 });
+    // TODO: `Arc` isn't enough if you want a **mutable** shared state.
+    let status = Arc::new(JobStatus { jobs_done: 0 });
 
-    let mut handles = vec![];
+    let mut handles = Vec::new();
     for _ in 0..10 {
         let status_shared = Arc::clone(&status);
         let handle = thread::spawn(move || {
             thread::sleep(Duration::from_millis(250));
-            // TODO: You must take an action before you update a shared value
-            status_shared.jobs_completed += 1;
+
+            // TODO: You must take an action before you update a shared value.
+            status_shared.jobs_done += 1;
         });
         handles.push(handle);
     }
 
-    // Waiting for all jobs to complete
+    // Waiting for all jobs to complete.
     for handle in handles {
         handle.join().unwrap();
     }
 
-    // TODO: Print the value of `JobStatus.jobs_completed`
-    println!("Jobs completed: {}", ???);
+    // TODO: Print the value of `JobStatus.jobs_done`.
+    println!("Jobs done: {}", todo!());
 }

exercises/20_threads/threads3.rs

@@ -1,7 +1,4 @@
-use std::sync::mpsc;
-use std::sync::Arc;
-use std::thread;
-use std::time::Duration;
+use std::{sync::mpsc, thread, time::Duration};
 
 struct Queue {
     length: u32,
@@ -11,7 +8,7 @@ struct Queue {
 
 impl Queue {
     fn new() -> Self {
-        Queue {
+        Self {
             length: 10,
             first_half: vec![1, 2, 3, 4, 5],
             second_half: vec![6, 7, 8, 9, 10],
@@ -19,20 +16,22 @@ impl Queue {
     }
 }
 
-fn send_tx(q: Queue, tx: mpsc::Sender<u32>) -> () {
+fn send_tx(q: Queue, tx: mpsc::Sender<u32>) {
+    // TODO: We want to send `tx` to both threads. But currently, it is moved
+    // into the frist thread. How could you solve this problem?
     thread::spawn(move || {
         for val in q.first_half {
-            println!("sending {:?}", val);
+            println!("Sending {val:?}");
             tx.send(val).unwrap();
-            thread::sleep(Duration::from_secs(1));
+            thread::sleep(Duration::from_millis(250));
         }
     });
 
     thread::spawn(move || {
         for val in q.second_half {
-            println!("sending {:?}", val);
+            println!("Sending {val:?}");
             tx.send(val).unwrap();
-            thread::sleep(Duration::from_secs(1));
+            thread::sleep(Duration::from_millis(250));
         }
     });
 }
@@ -55,11 +54,11 @@ mod tests {
 
         let mut total_received: u32 = 0;
         for received in rx {
-            println!("Got: {}", received);
+            println!("Got: {received}");
             total_received += 1;
         }
 
-        println!("total numbers received: {}", total_received);
+        println!("Number of received values: {total_received}");
         assert_eq!(total_received, queue_length);
     }
 }

exercises/21_macros/macros1.rs

@@ -5,5 +5,6 @@ macro_rules! my_macro {
 }
 
 fn main() {
+    // TODO: Fix the macro call.
     my_macro();
 }

exercises/21_macros/macros2.rs

@@ -2,6 +2,7 @@ fn main() {
     my_macro!();
 }
 
+// TODO: Fix the compiler error by moving the whole definition of this macro.
 macro_rules! my_macro {
     () => {
         println!("Check out my macro!");

exercises/21_macros/macros3.rs

@@ -1,5 +1,5 @@
-// Make me compile, without taking the macro out of the module!
-
+// TODO: Fix the compiler error without taking the macro definition out of this
+// module.
 mod macros {
     macro_rules! my_macro {
         () => {

exercises/21_macros/macros4.rs

@@ -1,3 +1,4 @@
+// TODO: Fix the compiler error by adding one or two characters.
 #[rustfmt::skip]
 macro_rules! my_macro {
     () => {

exercises/22_clippy/clippy1.rs

@@ -1,19 +1,17 @@
 // The Clippy tool is a collection of lints to analyze your code so you can
 // catch common mistakes and improve your Rust code.
 //
-// For these exercises the code will fail to compile when there are Clippy
+// For these exercises, the code will fail to compile when there are Clippy
 // warnings. Check Clippy's suggestions from the output to solve the exercise.
 
-use std::f32;
+use std::f32::consts::PI;
 
 fn main() {
-    let pi = 3.14f32;
-    let radius = 5.00f32;
+    // Use the more accurate `PI` constant.
+    let pi = PI;
+    let radius: f32 = 5.0;
 
-    let area = pi * f32::powi(radius, 2);
+    let area = pi * radius.powi(2);
 
-    println!(
-        "The area of a circle with radius {:.2} is {:.5}!",
-        radius, area
-    )
+    println!("The area of a circle with radius {radius:.2} is {area:.5}");
 }

exercises/22_clippy/clippy2.rs

@@ -1,8 +1,10 @@
 fn main() {
     let mut res = 42;
     let option = Some(12);
+    // TODO: Fix the Clippy lint.
     for x in option {
         res += x;
     }
-    println!("{}", res);
+
+    println!("{res}");
 }

exercises/22_clippy/clippy3.rs

@@ -1,25 +1,27 @@
-// Here's a couple more easy Clippy fixes, so you can see its utility.
+// Here are some more easy Clippy fixes so you can see its utility 📎
+// TODO: Fix all the Clippy lints.
 
+#[rustfmt::skip]
 #[allow(unused_variables, unused_assignments)]
 fn main() {
     let my_option: Option<()> = None;
     if my_option.is_none() {
-        my_option.unwrap();
+        println!("{:?}", my_option.unwrap());
     }
 
     let my_arr = &[
         -1, -2, -3
         -4, -5, -6
     ];
-    println!("My array! Here it is: {:?}", my_arr);
+    println!("My array! Here it is: {my_arr:?}");
 
     let my_empty_vec = vec![1, 2, 3, 4, 5].resize(0, 5);
-    println!("This Vec is empty, see? {:?}", my_empty_vec);
+    println!("This Vec is empty, see? {my_empty_vec:?}");
 
     let mut value_a = 45;
     let mut value_b = 66;
     // Let's swap these two!
     value_a = value_b;
     value_b = value_a;
-    println!("value a: {}; value b: {}", value_a, value_b);
+    println!("value a: {value_a}; value b: {value_b}");
 }

rustlings-macros/info.toml

@@ -1037,7 +1037,7 @@ hint = """
 https://doc.rust-lang.org/std/thread/fn.spawn.html
 
 A challenge with multi-threaded applications is that the main thread can
-finish before the spawned threads are completed.
+finish before the spawned threads are done.
 https://doc.rust-lang.org/book/ch16-01-threads.html#waiting-for-all-threads-to-finish-using-join-handles
 
 Use the `JoinHandle`s to wait for each thread to finish and collect their
@@ -1051,19 +1051,19 @@ dir = "20_threads"
 test = false
 hint = """
 `Arc` is an Atomic Reference Counted pointer that allows safe, shared access
-to **immutable** data. But we want to *change* the number of `jobs_completed`
-so we'll need to also use another type that will only allow one thread to
-mutate the data at a time. Take a look at this section of the book:
+to **immutable** data. But we want to *change* the number of `jobs_done` so
+we'll need to also use another type that will only allow one thread to mutate
+the data at a time. Take a look at this section of the book:
 https://doc.rust-lang.org/book/ch16-03-shared-state.html#atomic-reference-counting-with-arct
 
 Keep reading if you'd like more hints :)
 
 Do you now have an `Arc<Mutex<JobStatus>>` at the beginning of `main`? Like:
 ```
-let status = Arc::new(Mutex::new(JobStatus { jobs_completed: 0 }));
+let status = Arc::new(Mutex::new(JobStatus { jobs_done: 0 }));
 ```
 
-Similar to the code in the following example in the book:
+Similar to the code in the following example in The Book:
 https://doc.rust-lang.org/book/ch16-03-shared-state.html#sharing-a-mutext-between-multiple-threads"""
 
 [[exercises]]
@@ -1076,10 +1076,11 @@ An alternate way to handle concurrency between threads is to use an `mpsc`
 With both a sending end and a receiving end, it's possible to send values in
 one thread and receive them in another.
 
-Multiple producers are possible by using clone() to create a duplicate of the
+Multiple producers are possible by using `clone()` to create a duplicate of the
 original sending end.
 
-See https://doc.rust-lang.org/book/ch16-02-message-passing.html for more info."""
+Related section in The Book:
+https://doc.rust-lang.org/book/ch16-02-message-passing.html"""
 
 # MACROS
 
@@ -1088,9 +1089,8 @@ name = "macros1"
 dir = "21_macros"
 test = false
 hint = """
-When you call a macro, you need to add something special compared to a
-regular function call. If you're stuck, take a look at what's inside
-`my_macro`."""
+When you call a macro, you need to add something special compared to a regular
+function call."""
 
 [[exercises]]
 name = "macros2"
@@ -1109,10 +1109,7 @@ dir = "21_macros"
 test = false
 hint = """
 In order to use a macro outside of its module, you need to do something
-special to the module to lift the macro out into its parent.
-
-The same trick also works on "extern crate" statements for crates that have
-exported macros, if you've seen any of those around."""
+special to the module to lift the macro out into its parent."""
 
 [[exercises]]
 name = "macros4"
@@ -1137,7 +1134,7 @@ dir = "22_clippy"
 test = false
 strict_clippy = true
 hint = """
-Rust stores the highest precision version of any long or infinite precision
+Rust stores the highest precision version of some long or infinite precision
 mathematical constants in the Rust standard library:
 https://doc.rust-lang.org/stable/std/f32/consts/index.html
 
@@ -1145,7 +1142,7 @@ We may be tempted to use our own approximations for certain mathematical
 constants, but clippy recognizes those imprecise mathematical constants as a
 source of potential error.
 
-See the suggestions of the clippy warning in compile output and use the
+See the suggestions of the Clippy warning in the compile output and use the
 appropriate replacement constant from `std::f32::consts`..."""
 
 [[exercises]]
@@ -1154,7 +1151,8 @@ dir = "22_clippy"
 test = false
 strict_clippy = true
 hint = """
-`for` loops over `Option` values are more clearly expressed as an `if let`"""
+`for` loops over `Option` values are more clearly expressed as an `if-let`
+statement."""
 
 [[exercises]]
 name = "clippy3"

solutions/20_threads/threads1.rs

@@ -1 +1,37 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// This program spawns multiple threads that each run for at least 250ms, and
+// each thread returns how much time they took to complete. The program should
+// wait until all the spawned threads have finished and should collect their
+// return values into a vector.
+
+use std::{
+    thread,
+    time::{Duration, Instant},
+};
+
+fn main() {
+    let mut handles = Vec::new();
+    for i in 0..10 {
+        let handle = thread::spawn(move || {
+            let start = Instant::now();
+            thread::sleep(Duration::from_millis(250));
+            println!("Thread {i} done");
+            start.elapsed().as_millis()
+        });
+        handles.push(handle);
+    }
+
+    let mut results = Vec::new();
+    for handle in handles {
+        // Collect the results of all threads into the `results` vector.
+        results.push(handle.join().unwrap());
+    }
+
+    if results.len() != 10 {
+        panic!("Oh no! Some thread isn't done yet!");
+    }
+
+    println!();
+    for (i, result) in results.into_iter().enumerate() {
+        println!("Thread {i} took {result}ms");
+    }
+}

solutions/20_threads/threads2.rs

@@ -1 +1,41 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// Building on the last exercise, we want all of the threads to complete their
+// work. But this time, the spawned threads need to be in charge of updating a
+// shared value: `JobStatus.jobs_done`
+
+use std::{
+    sync::{Arc, Mutex},
+    thread,
+    time::Duration,
+};
+
+struct JobStatus {
+    jobs_done: u32,
+}
+
+fn main() {
+    // `Arc` isn't enough if you want a **mutable** shared state.
+    // We need to wrap the value with a `Mutex`.
+    let status = Arc::new(Mutex::new(JobStatus { jobs_done: 0 }));
+    //                    ^^^^^^^^^^^                          ^
+
+    let mut handles = Vec::new();
+    for _ in 0..10 {
+        let status_shared = Arc::clone(&status);
+        let handle = thread::spawn(move || {
+            thread::sleep(Duration::from_millis(250));
+
+            // Lock before you update a shared value.
+            status_shared.lock().unwrap().jobs_done += 1;
+            //           ^^^^^^^^^^^^^^^^
+        });
+        handles.push(handle);
+    }
+
+    // Waiting for all jobs to complete.
+    for handle in handles {
+        handle.join().unwrap();
+    }
+
+    println!("Jobs done: {}", status.lock().unwrap().jobs_done);
+    //                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+}

solutions/20_threads/threads3.rs

@@ -1 +1,66 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+use std::{sync::mpsc, thread, time::Duration};
+
+struct Queue {
+    length: u32,
+    first_half: Vec<u32>,
+    second_half: Vec<u32>,
+}
+
+impl Queue {
+    fn new() -> Self {
+        Self {
+            length: 10,
+            first_half: vec![1, 2, 3, 4, 5],
+            second_half: vec![6, 7, 8, 9, 10],
+        }
+    }
+}
+
+fn send_tx(q: Queue, tx: mpsc::Sender<u32>) {
+    // Clone the sender `tx` first.
+    let tx_clone = tx.clone();
+    thread::spawn(move || {
+        for val in q.first_half {
+            println!("Sending {val:?}");
+            // Then use the clone in the first thread. This means that
+            // `tx_clone` is moved to the first thread and `tx` to the second.
+            tx_clone.send(val).unwrap();
+            thread::sleep(Duration::from_millis(250));
+        }
+    });
+
+    thread::spawn(move || {
+        for val in q.second_half {
+            println!("Sending {val:?}");
+            tx.send(val).unwrap();
+            thread::sleep(Duration::from_millis(250));
+        }
+    });
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn threads3() {
+        let (tx, rx) = mpsc::channel();
+        let queue = Queue::new();
+        let queue_length = queue.length;
+
+        send_tx(queue, tx);
+
+        let mut total_received: u32 = 0;
+        for received in rx {
+            println!("Got: {received}");
+            total_received += 1;
+        }
+
+        println!("Number of received values: {total_received}");
+        assert_eq!(total_received, queue_length);
+    }
+}

solutions/21_macros/macros1.rs

@@ -1 +1,10 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+macro_rules! my_macro {
+    () => {
+        println!("Check out my macro!");
+    };
+}
+
+fn main() {
+    my_macro!();
+    //      ^
+}

solutions/21_macros/macros2.rs

@@ -1 +1,10 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// Moved the macro definition to be before its call.
+macro_rules! my_macro {
+    () => {
+        println!("Check out my macro!");
+    };
+}
+
+fn main() {
+    my_macro!();
+}

solutions/21_macros/macros3.rs

@@ -1 +1,13 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// Added the attribute `macro_use` attribute.
+#[macro_use]
+mod macros {
+    macro_rules! my_macro {
+        () => {
+            println!("Check out my macro!");
+        };
+    }
+}
+
+fn main() {
+    my_macro!();
+}

solutions/21_macros/macros4.rs

@@ -1 +1,15 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// Added semicolons to separate the macro arms.
+#[rustfmt::skip]
+macro_rules! my_macro {
+    () => {
+        println!("Check out my macro!");
+    };
+    ($val:expr) => {
+        println!("Look at this other macro: {}", $val);
+    };
+}
+
+fn main() {
+    my_macro!();
+    my_macro!(7777);
+}

solutions/22_clippy/clippy1.rs

@@ -1 +1,17 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// The Clippy tool is a collection of lints to analyze your code so you can
+// catch common mistakes and improve your Rust code.
+//
+// For these exercises, the code will fail to compile when there are Clippy
+// warnings. Check Clippy's suggestions from the output to solve the exercise.
+
+use std::f32::consts::PI;
+
+fn main() {
+    // Use the more accurate `PI` constant.
+    let pi = PI;
+    let radius: f32 = 5.0;
+
+    let area = pi * radius.powi(2);
+
+    println!("The area of a circle with radius {radius:.2} is {area:.5}");
+}

solutions/22_clippy/clippy2.rs

@@ -1 +1,10 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+fn main() {
+    let mut res = 42;
+    let option = Some(12);
+    // Use `if-let` instead of iteration.
+    if let Some(x) = option {
+        res += x;
+    }
+
+    println!("{res}");
+}

solutions/22_clippy/clippy3.rs

@@ -1 +1,31 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+use std::mem;
+
+#[rustfmt::skip]
+#[allow(unused_variables, unused_assignments)]
+fn main() {
+    let my_option: Option<()> = None;
+    // `unwrap` of an `Option` after checking if it is `None` will panic.
+    // Use `if-let` instead.
+    if let Some(value) = my_option {
+        println!("{value:?}");
+    }
+
+    // A comma was missing.
+    let my_arr = &[
+        -1, -2, -3,
+        -4, -5, -6,
+    ];
+    println!("My array! Here it is: {:?}", my_arr);
+
+    let mut my_empty_vec = vec![1, 2, 3, 4, 5];
+    // `resize` mutates a vector instead of returning a new one.
+    // `resize(0, …)` clears a vector, so it is better to use `clear`.
+    my_empty_vec.clear();
+    println!("This Vec is empty, see? {my_empty_vec:?}");
+
+    let mut value_a = 45;
+    let mut value_b = 66;
+    // Use `mem::swap` to correctly swap two values.
+    mem::swap(&mut value_a, &mut value_b);
+    println!("value a: {}; value b: {}", value_a, value_b);
+}