A contiguous growable array type with heap-allocated contents, written Vec<T>.

Vectors have O(1) indexing, amortized O(1) push (to the end) and O(1) pop (from the end).

Vectors ensure they never allocate more than isize::MAX bytes.

Examples

You can explicitly create a Vec with [Vec::new]:

let v: Vec<i32> = Vec::new();

...or by using the [vec!] macro:

let v: Vec<i32> = vec![];

let v = vec![1, 2, 3, 4, 5];

let v = vec![0; 10]; // ten zeroes

You can push values onto the end of a vector (which will grow the vector as needed):

let mut v = vec![1, 2];

v.push(3);

Popping values works in much the same way:

let mut v = vec![1, 2];

let two = v.pop();

Vectors also support indexing (through the Index and IndexMut traits):

let mut v = vec![1, 2, 3];
let three = v[2];
v[1] = v[1] + 5;

Memory layout

When the type is non-zero-sized and the capacity is nonzero, Vec uses the Global allocator for its allocation. It is valid to convert both ways between such a Vec and a raw pointer allocated with the Global allocator, provided that the Layout used with the allocator is correct for a sequence of capacity elements of the type, and the first len values pointed to by the raw pointer are valid. More precisely, a ptr: *mut T that has been allocated with the Global allocator with Layout::array::<T>(capacity) may be converted into a vec using Vec::<T>::from_raw_parts(ptr, len, capacity). Conversely, the memory backing a value: *mut T obtained from [Vec::<T>::as_mut_ptr] may be deallocated using the Global allocator with the same layout.

For zero-sized types (ZSTs), or when the capacity is zero, the Vec pointer must be non-null and sufficiently aligned. The recommended way to build a Vec of ZSTs if [vec!] cannot be used is to use ptr::NonNull::dangling.