fn bar() {
    let mut a = vec![1,2,3];
    let b = &mut a;
    let c = &mut *b;

    c[0] = 4;

    for val in c.iter() {
        println!("{}", val);
    }

    println!("=========");

    for val in b.iter() {
        println!("{}", val);
    }

    println!("=========");

    for val in a.iter() {
        println!("{}", val);
    }
}

fn main() {
    bar();
}