19_matching_option.rs

fn main() {
    let five = Some(5);
    let six = plus_one(five);
    let none = plus_one(None);

    println!("{:?} {:?} {:?}", five, six, none);

}

fn plus_one(x: Option<i32>) -> Option<i32> {
    match x {
        Some(i) => Some(i+1),
        _ => None,
    }
}