Rust: The pointer and the box it points to

mutable_pointers.rs

struct Point { x: int, y:int }

fn main() {

    // Local variable, easy
    let mut p1 = Point{x:1, y:2};
    p1.x = 10;

    // Owned pointer
    // also easy because target inherts mutability
    let mut p2 = ~Point{x:1, y:2};
    p2.x = 10;

    // Managed pointer

    // Not so easy. This won't work
    let mut pNO = @Point{x:1, y:2};
    pNO.x = 10;   // You could change pNO, but not pNO.x

    // Need to make the contents mutable. 
    // Do not need to make the variable
    // itself mutable - you can
    // change p.x, but not p.
    let p3 = @mut Point{x:1, y:2};
    p3.x = 10;

    println(fmt!("%d, %d, %d", p1.x, p2.x, p3.x));
}