enum_fmt.rs

#[feature(macro_rules)];
macro_rules! enum_fmt(
    ($name:ident { $($member:ident),+ }) => (
        enum $name {
        $(
            $member,
        )+
        }
        
        impl std::fmt::Default for $name {
            fn fmt(obj: &$name, f: &mut std::fmt::Formatter) {
                let s = match *obj {
                $(
                    $member => "$member",
                )+
                };
                f.buf.write(s.as_bytes())
            }
        }
    )
)

enum_fmt!(Direction {
    East,
    West,
    North,
    South
}
)

fn main() {
    println!("{} {}", East, West)
}