Collections in Rust

Last updated Dec 1, 2022 Edit Source

• Rust
• Programming

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Vec<T> -> Vector.

Vecors are the most commonly used collection.

Define the vector type in the <>

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let mut v: Vec<i32> = Vec::new();
v.push(2);
v.push(4);
v.push(6);
let x = v.pop(); // x is 6
println!("{}",v[1]); //prints 4

Vectors are used in rust where you would use lists or arrays in other languages. vectors act like a stack so push appends item to end, pop removes item from end and returns it.

Because vectors store items of known size next to each other in memory you can index into one just like an array.

if index is out of bounds rust will panic.

There is a macro called vec that makes creating vectors from literal values easy.

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let mut v = vec![2,4,6];

there are tons of methods to manipulate vectors in the standard library.

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HashMap<K,V>

In other languages this might be called a dictionary. Its used to insert remove and look up values by key and value.

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let mut h: HashMap<u8,bool> = HashMap::new();
h.insert(5,true);
h.insert(6,false);
let have_five = h.remove(&5).unwrap();

you can insert entries with insert remove entries with the remove method.

remove returns and enum called option!

there are other methods to get stuff from these.

Uses ring buffer to implement a double ended queue can efficiently add or remove items from the front and back. everything else is a little less efficient than regular vector.

quick at adding or removing items at an arbitrary point in the list but slow doing anything else.

A hashing implementation of a set that performs set operations really efficiently.

Like a priority queue that always pops off the max value.

alternate map and set implementations using a modified binary tree. Usually only choose these over the hash variants if you need the map keys or set variants to always be sorted.