macro_rules! calculate{
    (eval $e:expr) =>{
        {
            let val:usize = $e;
            println!("{} = {}",stringify!($e),val);
        }
    };
    (eval $e:expr, $(eval $es:expr),+) =>{
            calculate!{
                eval $e
            }
            calculate!{
                $(eval $es),+
            }
    }
}
fn main() {
    calculate! {
        eval 1 + 2,
        eval 2* 3,
        eval 4/2
    }
}