#[derive(Debug, Serialize)]
enum ArithExp{
    Sum{
        lhs: Box<ArithExp>,
        rhs: Box<ArithExp>
    },
    Mul {
        lhs: Box<ArithExp>,
        rhs: Box<ArithExp>
    },
    Num {
        value: f64
    },
}

fn num(value: f64) -> std::boxed::Box<ArithExp>{
    Box::new(ArithExp::Num { value })
}

fn main() {
    let number = num(1.0);
    match *number {
        ArithExp::Num{value} => println!("VALUE = {}", value),
        _ => ()
    }
    println!("{:?}", number);

}