feat: add async exercises

Author: manyinsects

dev/Cargo.toml

@@ -164,30 +164,34 @@ bin = [
   { name = "threads2_sol", path = "../solutions/20_threads/threads2.rs" },
   { name = "threads3", path = "../exercises/20_threads/threads3.rs" },
   { name = "threads3_sol", path = "../solutions/20_threads/threads3.rs" },
-  { name = "macros1", path = "../exercises/21_macros/macros1.rs" },
-  { name = "macros1_sol", path = "../solutions/21_macros/macros1.rs" },
-  { name = "macros2", path = "../exercises/21_macros/macros2.rs" },
-  { name = "macros2_sol", path = "../solutions/21_macros/macros2.rs" },
-  { name = "macros3", path = "../exercises/21_macros/macros3.rs" },
-  { name = "macros3_sol", path = "../solutions/21_macros/macros3.rs" },
-  { name = "macros4", path = "../exercises/21_macros/macros4.rs" },
-  { name = "macros4_sol", path = "../solutions/21_macros/macros4.rs" },
-  { name = "clippy1", path = "../exercises/22_clippy/clippy1.rs" },
-  { name = "clippy1_sol", path = "../solutions/22_clippy/clippy1.rs" },
-  { name = "clippy2", path = "../exercises/22_clippy/clippy2.rs" },
-  { name = "clippy2_sol", path = "../solutions/22_clippy/clippy2.rs" },
-  { name = "clippy3", path = "../exercises/22_clippy/clippy3.rs" },
-  { name = "clippy3_sol", path = "../solutions/22_clippy/clippy3.rs" },
-  { name = "using_as", path = "../exercises/23_conversions/using_as.rs" },
-  { name = "using_as_sol", path = "../solutions/23_conversions/using_as.rs" },
-  { name = "from_into", path = "../exercises/23_conversions/from_into.rs" },
-  { name = "from_into_sol", path = "../solutions/23_conversions/from_into.rs" },
-  { name = "from_str", path = "../exercises/23_conversions/from_str.rs" },
-  { name = "from_str_sol", path = "../solutions/23_conversions/from_str.rs" },
-  { name = "try_from_into", path = "../exercises/23_conversions/try_from_into.rs" },
-  { name = "try_from_into_sol", path = "../solutions/23_conversions/try_from_into.rs" },
-  { name = "as_ref_mut", path = "../exercises/23_conversions/as_ref_mut.rs" },
-  { name = "as_ref_mut_sol", path = "../solutions/23_conversions/as_ref_mut.rs" },
+  { name = "async1", path = "../exercises/21_async/async1.rs" },
+  { name = "async1_sol", path = "../solutions/21_async/async1.rs" },
+  { name = "async2", path = "../exercises/21_async/async2.rs" },
+  { name = "async2_sol", path = "../solutions/21_async/async2.rs" },
+  { name = "macros1", path = "../exercises/22_macros/macros1.rs" },
+  { name = "macros1_sol", path = "../solutions/22_macros/macros1.rs" },
+  { name = "macros2", path = "../exercises/22_macros/macros2.rs" },
+  { name = "macros2_sol", path = "../solutions/22_macros/macros2.rs" },
+  { name = "macros3", path = "../exercises/22_macros/macros3.rs" },
+  { name = "macros3_sol", path = "../solutions/22_macros/macros3.rs" },
+  { name = "macros4", path = "../exercises/22_macros/macros4.rs" },
+  { name = "macros4_sol", path = "../solutions/22_macros/macros4.rs" },
+  { name = "clippy1", path = "../exercises/23_clippy/clippy1.rs" },
+  { name = "clippy1_sol", path = "../solutions/23_clippy/clippy1.rs" },
+  { name = "clippy2", path = "../exercises/23_clippy/clippy2.rs" },
+  { name = "clippy2_sol", path = "../solutions/23_clippy/clippy2.rs" },
+  { name = "clippy3", path = "../exercises/23_clippy/clippy3.rs" },
+  { name = "clippy3_sol", path = "../solutions/23_clippy/clippy3.rs" },
+  { name = "using_as", path = "../exercises/24_conversions/using_as.rs" },
+  { name = "using_as_sol", path = "../solutions/24_conversions/using_as.rs" },
+  { name = "from_into", path = "../exercises/24_conversions/from_into.rs" },
+  { name = "from_into_sol", path = "../solutions/24_conversions/from_into.rs" },
+  { name = "from_str", path = "../exercises/24_conversions/from_str.rs" },
+  { name = "from_str_sol", path = "../solutions/24_conversions/from_str.rs" },
+  { name = "try_from_into", path = "../exercises/24_conversions/try_from_into.rs" },
+  { name = "try_from_into_sol", path = "../solutions/24_conversions/try_from_into.rs" },
+  { name = "as_ref_mut", path = "../exercises/24_conversions/as_ref_mut.rs" },
+  { name = "as_ref_mut_sol", path = "../solutions/24_conversions/as_ref_mut.rs" },
 ]
 
 [package]
@@ -196,6 +200,9 @@ edition = "2024"
 # Don't publish the exercises on crates.io!
 publish = false
 
+[dependencies]
+tokio = { version = "1.45.0", features = ["rt-multi-thread", "macros"] }
+
 [profile.release]
 panic = "abort"
 

exercises/21_async/README.md

@@ -0,0 +1,10 @@
+# Async
+
+Rust includes built-in support for asynchronous programming. In other languages, this might be known as Promises or
+Coroutines. async programming uses async functions, which are powerful, but may require some getting used to,
+especially if you haven't used something similar in another language.
+
+The [relevant book chapter][1] is essential reading. The [tokio docs][2] are also very helpful!
+
+[1]: https://doc.rust-lang.org/book/ch17-00-async-await.html
+[2]: https://tokio.rs/tokio/tutorial

exercises/21_async/async1.rs

@@ -0,0 +1,44 @@
+// Our loyal worker works hard to create a new number.
+#[derive(Default)]
+struct Worker;
+
+struct NumberContainer {
+    number: i32,
+}
+
+impl Worker {
+    async fn work(&self) -> NumberContainer {
+        // Pretend this takes a while...
+        let new_number = 32;
+        NumberContainer { number: new_number }
+    }
+}
+
+impl NumberContainer {
+    async fn extract_number(&self) -> i32 {
+        // And this too...
+        self.number
+    }
+}
+
+// TODO: Fix the function signature!
+fn run_worker() -> i32 {
+    // TODO: Make our worker create a new number and return it.
+}
+
+fn main() {
+    // Feel free to experiment here. You may need to make some adjustments
+    // to this function, though.
+}
+
+mod tests {
+    use super::*;
+
+    // Don't worry about this attribute for now.
+    // If you want to know what this does, read the hint!
+    #[tokio::test]
+    async fn test_if_it_works() {
+        let number = run_worker().await;
+        assert_eq!(number, 32);
+    }
+}

exercises/21_async/async2.rs

@@ -0,0 +1,42 @@
+use tokio::task::JoinSet;
+
+// A MultiWorker can work with the power of 5 normal workers,
+// allowing us to create 5 new numbers at once!
+struct MultiWorker;
+
+impl MultiWorker {
+    async fn start_work(&self) -> JoinSet<i32> {
+        let mut set = JoinSet::new();
+
+        for i in 30..35 {
+            // TODO: `set.spawn` accepts an async function that will return the number
+            //       we want. Implement this function as a closure!
+            set.spawn(???);
+        }
+
+        set
+    }
+}
+
+async fn run_multi_worker() -> Vec<i32> {
+    let tasks = MultiWorker.start_work().await;
+
+    // TODO: We have a bunch of tasks, how do we run them to completion
+    //       to get at the i32s they create?
+}
+
+fn main() {
+    // Feel free to experiment here. You may need to make some adjustments
+    // to this function, though.
+}
+
+mod tests {
+    use super::*;
+
+    #[tokio::test]
+    async fn test_if_it_works() {
+        let mut numbers = run_multi_worker().await;
+        numbers.sort(); // in case tasks run out-of-order
+        assert_eq!(numbers, vec![30, 31, 32, 33, 34]);
+    }
+}