alloc::vec - Rust
Description: A contiguous growable array type with heap-allocated contents, written `Vec<T>`.

## Module vec

1.36.0 · Source
Expand description

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`.

## Structs§

Drain
  A draining iterator for `Vec<T>`.
ExtractIf
  An iterator which uses a closure to determine if an element should be removed.
IntoIter
  An iterator that moves out of a vector.
Splice
  A splicing iterator for `Vec`.
Vec
  A contiguous growable array type, written as `Vec<T>`, short for ‘vector’.
PeekMutExperimental
  Structure wrapping a mutable reference to the last item in a `Vec`.