fn main() {
    let x = 3;
    let y = x;
    let mut v = vec![2, 4];
    let w = v.clone();
    println!("Hello, world! {} {}, {:?} {:?}", x, y, v, w);
    v.push(4);
    println!("v is now {:?}", v);
    println!("w is now {:?}", w);
    println!("max of v is {}", max(&v).expect("Expected a max"));
}

fn max(v: &[i32]) -> Option<i32>
{
    if v.len() == 0 {
        return None;
    }
    let mut i = v[0];
    for &j in v {
        if j > i {
            i = j;
        }
    }
    Some(i)
}