Collections

The stdlib provides hash-based collection types:

• HashMap:<K, V>
• HashSet:<T>
• HashMapIter:<K, V>
• HashSetIter:<T>

HashMap:<K, V> stores key-value pairs.

let mut map := HashMap:<str, int>.new();
map["a"] := 10;
map["b"] := 20;

print(map["a"]);
print("a" in map);
print(map.len());

Important HashMap methods include:

• .set(...)
• .get(...)
• .remove(...)
• .contains(...)
• .len()
• .is_empty()
• .keys()
• .values()
• .entries()
• .clear()
• .set_all(...)
• .get_or(...)
• .iter()
• .into_iter()

HashSet:<T> stores unique values.

let mut set := HashSet:<int>.new(50, 60, 30);
set.add(10);
set.add(20);

print(10 in set);
print(set.contains(20));
print(set.len());

Important HashSet methods include:

• .add(...)
• .remove(...)
• .contains(...)
• .len()
• .is_empty()
• .values()
• .clear()
• .iter()
• .into_iter()

The iterator types HashMapIter and HashSetIter implement the iterator trait, so you can call .next() manually or use the usual iterator helpers.

let mut it := map.into_iter();
print(it.next());

Use HashMap when values are looked up by key, and HashSet when you only care whether a value is present.