rust Option枚举

枚举

fn main() {
    let a_binding;
    {
        let x = 2;
        a_binding = x * x;
    }
    println!("a binding: {}", a_binding);

    let sn = Some(5);
    let ss = Some("a string");
    let absn: Option<i32> = None;
    println!("{:?}:{:?}:{:?}",sn,ss,absn);

    fn ps1(n: Option<i32>) -> Option<i32> {
        match n {
            None => None,
            Some(i) => Some(i+1), // 这里如果写作Some(i)+1，会出错，Some（i）为Option<i32>类型，1是<i32>类型
        }
    }
    let six=ps1(sn);
    let none=ps1(absn);
    println!("{:?}:{:?}",six,none);
}