Improve speaker notes and exercise in tuples and arrays section (#2909)

src/tuples-and-arrays/arrays.md

@@ -57,6 +57,17 @@ fn main() {
 
 - We can use literals to assign values to arrays.
 
+- Arrays are not heap-allocated. They are regular values with a fixed size known
+  at compile time, meaning they go on the stack. This can be different from what
+  students expect if they come from a garbage-collected language, where arrays
+  may be heap allocated by default.
+
+- There is no way to remove elements from an array, nor add elements to an
+  array. The length of an array is fixed at compile-time, and so its length
+  cannot change at runtime.
+
+## Debug Printing
+
 - The `println!` macro asks for the debug implementation with the `?` format
   parameter: `{}` gives the default output, `{:?}` gives the debug output. Types
   such as integers and strings implement the default output, but arrays only
@@ -65,9 +76,4 @@ fn main() {
 - Adding `#`, eg `{a:#?}`, invokes a "pretty printing" format, which can be
   easier to read.
 
-- Arrays are not heap-allocated. They are regular values with a fixed size known
-  at compile time, meaning they go on the stack. This can be different from what
-  students expect if they come from a garbage-collected language, where arrays
-  may be heap allocated by default.
-
 </details>

src/tuples-and-arrays/exercise.rs

@@ -33,9 +33,17 @@ fn main() {
         [301, 302, 303],
     ];
 
-    dbg!(matrix);
+    println!("Original:");
+    for row in &matrix {
+        println!("{:?}", row);
+    }
+
     let transposed = transpose(matrix);
-    dbg!(transposed);
+
+    println!("\nTransposed:");
+    for row in &transposed {
+        println!("{:?}", row);
+    }
 }
 // ANCHOR_END: main
 // ANCHOR_END: solution

src/tuples-and-arrays/tuples.md

@@ -26,4 +26,11 @@ fn main() {
 - The empty tuple `()` is referred to as the "unit type" and signifies absence
   of a return value, akin to `void` in other languages.
 
+- Unlike arrays, tuples cannot be used in a `for` loop. This is because a `for`
+  loop requires all the elements to have the same type, which may not be the
+  case for a tuple.
+
+- There is no way to add or remove elements from a tuple. The number of elements
+  and their types are fixed at compile time and cannot be changed at runtime.
+
 </details>