Rust Basics

Rust Vectors: Vec<T>

A list that grows while the program runs: push, pop, sort and read items safely.

Beginner
2 min read
1 runnable example

What you'll learn

vec! and push
Indexing vs get
sort and pop

Run code →

vec![3, 1, 4] after two pushes

1push

5push

A Vec grows at the end.

A growable list

A vector, written Vec<T>, is a list that can grow and shrink while the program runs. It is the collection you will use most often in Rust.

vec! creates a vector with starting values and push adds to the end. numbers[2] stops the program if the index does not exist, while get returns None instead. pop removes the last item and returns it inside Some.

Key points

push adds to the end, pop removes from the end.
numbers[10] stops the program if the index is missing.
get(10) returns None instead.

Runnable Rust example

Rust

Run code →

main.rs

fn main() {
    let mut numbers = vec![3, 1, 4];
    numbers.push(1);
    numbers.push(5);

    println!("{:?}", numbers);
    println!("length: {}", numbers.len());
    println!("third: {}", numbers[2]);

    match numbers.get(10) {
        Some(value) => println!("found {value}"),
        None => println!("no item at index 10"),
    }

    numbers.sort();
    let last = numbers.pop();
    println!("{:?} after pop, removed {:?}", numbers, last);
}

Get a Run button for this example Result of running the code

[3, 1, 4, 1, 5]
length: 5
third: 4
no item at index 10
[1, 1, 3, 4] after pop, removed Some(5)

Practice

Open the example in the online compiler, change a value or add a line, and predict the output before you run it. Then break the code on purpose and read the compiler's message.

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