pub enum SomethingOrNothing<T>  {
    Something(T),
    Nothing,
}
pub use self::SomethingOrNothing::*;

pub trait Minimum : Copy {
    fn min(self, b: Self) -> Self;
}

pub fn vec_min<T/*: Minimum*/>(v: Vec<T>) -> SomethingOrNothing<T> {
    let mut min = Nothing;
    for e in v {
        min = Something(match min {
            Nothing => e,
            // Here, we can now call the `min` function of the trait.
            Something(n) => {
                e.min(n)
            }
        });
    }
    min
}

impl Minimum for i32 {
    fn min(self, b: Self) -> Self {
        if self < b { self } else { b }
    }
}

fn main() {
    let v = vec![18,5,7,3,9,27];
    let min = vec_min(v);
}