[Rust] Changing data in a vector with indexs.

fn main() {
    let mut vec = vec![1, 2, 3];

    for i in 0..vec.len() {
        vec[i] = vec[i] * vec[i];
    }

    assert_eq!(vec[0], 1);
    assert_eq!(vec[1], 4);
    assert_eq!(vec[2], 9);
}