trait HasDefault {

    fn default() -> Self;

}

struct DefaultOne;

impl Default for DefaultOne {
    fn default() -> Self {
        DefaultOne{}
    }
}

struct DefaultTwo;
impl Default for DefaultTwo {
    fn default() -> Self {
        DefaultTwo{}
    }
}

pub fn main() {
    println!("Hello");
    let v = vec![DefaultOne::default, DefaultTwo::default];
    let w = vec![DefaultOne::default(), DefaultTwo::default()];

    // Iterate over v or w using just methods in the Default trait
}