Rust code shared from the playground

playground.rs

enum Expr {
    Val(i32),
    Div(Box<Expr>, Box<Expr>),
}

fn eval(expr: Expr) -> Option<i32> {
    match expr {
        Expr::Val(x) => Some(x),
        Expr::Div(x, y) => {
            let x = eval(*x)?;
            let y = eval(*y)?;
            safediv(x, y)
        }
    }
}

fn safediv(x: i32, y: i32) -> Option<i32> {
    if y == 0 {
        None
    } else {
        Some(x / y)
    }
}

fn main() {
    println!("{:?}", eval(Expr::Val(10)));
    println!(
        "{:?}",
        eval(Expr::Div(Box::new(Expr::Val(10)), Box::new(Expr::Val(5))))
    );
    println!(
        "{:?}",
        eval(Expr::Div(Box::new(Expr::Val(10)), Box::new(Expr::Val(0))))
    );
}