Example of a macro in rust

macro.rs

#![feature(macro_rules)]

macro_rules! loop_x {
    ($e: expr) => {
        // $e will not interact with this 'x
        // refers to the 'x in the outside loop
        'x: loop {
            println!("Hello!");
            $e
        }
    }
}

fn main() {
    'x: loop {
        // the 'x passed into loop_x! refers to
        // the one that defines this current loop
        loop_x!(break 'x);
        println!("This will never print!");
        println!("Another thing that will never print!");
    }
}