string_macros.rs

macro_rules! join {
    ($($s:expr),+) => ({
        let mut agg = String::new();
        $(agg.push_str($s);)*
        agg
    });
}

macro_rules! repeat {
    ($s:expr, $n:expr) => ({
        let size = $s.len();
        let mut agg = String::with_capacity(size * $n);
        for _ in 0..$n {
            agg.push_str($s);
        }
        agg
    });
}

fn main() {
    println!("{}", repeat!("garrett", 7));
    println!("{}", join!("a", "b", "c"));
}