Example with lifetimes specified

src/main.rs

@@ -6,7 +6,11 @@ fn main() {
     println!("The longest string is {result}");
 }
 
-fn longest(a: &str, b: &str) -> &str {
+fn longest<'a, 'b, 'out>(a: &'a str, b: &'b str) -> &'out str
+where
+    'a: 'out,
+    'b: 'out,
+{
     if a.len() > b.len() {
         a
     } else {