Vector

A Vec struct contains a ptr to the head of the allocation in the heap, len and capacity.

            ptr      len  capacity
       +--------+--------+--------+
       | 0x0123 |      2 |      4 |
       +--------+--------+--------+
            |
            v
Heap   +--------+--------+--------+--------+
       |    'a' |    'b' | uninit | uninit |
       +--------+--------+--------+--------+

References:

• Vec in std::vec - Rust

Cheatsheet

let v0 = vec![1, 2, 3];
let v1 = vec![0; 10];
let v2 = Vec::from(arr1);  // arr1: [u8; 10], from array or slice
let v3: Vec<u8> = (0..10).collect();

let mut v1: Vec<i32> = (0..10).collect();
v1.push(11);
v1[10];
v1.len();
// get pop push insert
v1.iter();

Examples

Basic operations

get, set, len, push, pop, slice

test_vec.rs

#[test]
fn test_vec() {
    let mut v1 = vec![1, 2, 3];
    assert_eq!(v1.len(), 3);
    assert_eq!(v1, Vec::from([1, 2, 3]));
    assert_eq!(v1, [1, 2, 3]);
    v1[0] = 7;
    assert_eq!(v1[0], 7);

    let mut v2: Vec<i32> = Vec::new();
    v2.push(1);
    v2.push(2);
    v2.push(3);
    assert_eq!(v2.pop(), Some(3));

    match v2.get(5) {
        Some(_) => println!("get key"),
        None => println!("out of bound"),
    }
}

Advanced operations

#[test]
fn test_advanced_vec() {
    let mut vec = vec![0; 5];
    assert_eq!(vec, [0, 0, 0, 0, 0]);

    // extend with an iterator
    vec.extend([1, 2, 3].iter().copied());
}

Questions

Differences between 'array' and 'vector'

• Array is stored in the stack.
• Array has fixed length at compile time.
• For performance, array is a little bit faster than vector. Ref

Differences between 'slice' and 'vector'

Ref

A Vec indicates ownership of the memory, and a slice indicates a borrow of memory. A Vec needs to deallocate all the items and the chunk of memory when it is itself deallocated (dropped in Rust-speak). This happens when it goes out of scope. The slice does nothing when it is dropped.