rustbook/chapter6/matchoptions/src/main.rs

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


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