as_ref_mut solution

exercises/23_conversions/as_ref_mut.rs

@@ -3,22 +3,21 @@
 // https://doc.rust-lang.org/std/convert/trait.AsMut.html, respectively.
 
 // Obtain the number of bytes (not characters) in the given argument.
-// TODO: Add the AsRef trait appropriately as a trait bound.
+// TODO: Add the `AsRef` trait appropriately as a trait bound.
 fn byte_counter<T>(arg: T) -> usize {
     arg.as_ref().as_bytes().len()
 }
 
 // Obtain the number of characters (not bytes) in the given argument.
-// TODO: Add the AsRef trait appropriately as a trait bound.
+// TODO: Add the `AsRef` trait appropriately as a trait bound.
 fn char_counter<T>(arg: T) -> usize {
     arg.as_ref().chars().count()
 }
 
-// Squares a number using as_mut().
+// Squares a number using `as_mut()`.
 // TODO: Add the appropriate trait bound.
 fn num_sq<T>(arg: &mut T) {
     // TODO: Implement the function body.
-    ???
 }
 
 fn main() {

solutions/23_conversions/as_ref_mut.rs

@@ -1 +1,59 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// AsRef and AsMut allow for cheap reference-to-reference conversions. Read more
+// about them at https://doc.rust-lang.org/std/convert/trait.AsRef.html and
+// https://doc.rust-lang.org/std/convert/trait.AsMut.html, respectively.
+
+// Obtain the number of bytes (not characters) in the given argument.
+fn byte_counter<T: AsRef<str>>(arg: T) -> usize {
+    arg.as_ref().as_bytes().len()
+}
+
+// Obtain the number of characters (not bytes) in the given argument.
+fn char_counter<T: AsRef<str>>(arg: T) -> usize {
+    arg.as_ref().chars().count()
+}
+
+// Squares a number using `as_mut()`.
+fn num_sq<T: AsMut<u32>>(arg: &mut T) {
+    let arg = arg.as_mut();
+    *arg = *arg * *arg;
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn different_counts() {
+        let s = "Café au lait";
+        assert_ne!(char_counter(s), byte_counter(s));
+    }
+
+    #[test]
+    fn same_counts() {
+        let s = "Cafe au lait";
+        assert_eq!(char_counter(s), byte_counter(s));
+    }
+
+    #[test]
+    fn different_counts_using_string() {
+        let s = String::from("Café au lait");
+        assert_ne!(char_counter(s.clone()), byte_counter(s));
+    }
+
+    #[test]
+    fn same_counts_using_string() {
+        let s = String::from("Cafe au lait");
+        assert_eq!(char_counter(s.clone()), byte_counter(s));
+    }
+
+    #[test]
+    fn mut_box() {
+        let mut num: Box<u32> = Box::new(3);
+        num_sq(&mut num);
+        assert_eq!(*num, 9);
+    }
+}