+
+ // hash maps
+ let mut scores = HashMap::new();
+ scores.insert("john", 10);
+ scores.insert("mary", 20);
+
+ println!("scores: {:?}", scores);
+
+ // hash map with .collect()
+ let persons = vec![("homer", 42), ("marge", 30)];
+ let collect_scores: HashMap<_, _> = persons.into_iter().collect();
+ println!("collect_scores: {:?}", collect_scores);
+
+ for (p, s) in &collect_scores {
+ println!("person {}: score {}", p, s);
+ }
+
+ println!("john's score: {}", scores.get("john").unwrap());
+ println!("jake's score: {}", scores.get("jake").unwrap_or(&-1));
+
+ // double scores
+ for (_, v) in scores.iter_mut() {
+ *v *= 2;
+ }
+ println!("scores after doubling: {:?}", scores);
+
+ // double scores of immutable hashmap (rebuild it)
+ let collect_scores: HashMap<_, _> = collect_scores.iter()
+ .map(|(k, v)| (k, 2 * v))
+ .collect();
+ println!("collect_scores after rebuilding with doubling: {:?}", collect_scores);