vec_box!

A small macro to box up elements in an array for use with trait objects.

Example

```rust

[macro_use]

extern crate vec_box;

struct A { x: u32 }

impl A { fn new(x: u32) -> A { A { x: x } } }

struct B { x: u32, y: u32 }

impl B { fn new(x: u32) -> B { B { x: x, y: x } } }

trait C { fn get(&self) -> u32; }

impl C for A { fn get(&self) -> u32 { self.x } }

impl C for B { fn get(&self) -> u32 { self.x + self.y } }

fn main() { let v: Vec> = vec_box![ A::new(1), B::new(1), A::new(2) ];

assert_eq!(
    v.iter().fold(0, |acc, ref x| acc + x.get()),
    5
);

} ```