Module std::boxedStable [-] [+] [src]

A pointer type for heap allocation.

Box<T>, casually referred to as a 'box', provides the simplest form of heap allocation in Rust. Boxes provide ownership for this allocation, and drop their contents when they go out of scope.

Boxes are useful in two situations: recursive data structures, and occasionally when returning data. The Pointer chapter of the Book explains these cases in detail.

Examples

Creating a box:

fn main() { let x = Box::new(5); }

let x = Box::new(5);

Creating a recursive data structure:

#[derive(Debug)] enum List<T> { Cons(T, Box<List<T>>), Nil, } fn main() { let list: List<i32> = List::Cons(1, Box::new(List::Cons(2, Box::new(List::Nil)))); println!("{:?}", list); }

#[derive(Debug)]
enum List<T> {
    Cons(T, Box<List<T>>),
    Nil,
}

fn main() {
    let list: List<i32> = List::Cons(1, Box::new(List::Cons(2, Box::new(List::Nil))));
    println!("{:?}", list);
}