// Reverse a string with runes
fn main() {
    let r: String = "一二三四五六七八九十".chars().rev().collect();
    println!("original    {:?}", "一二三四五六七八九十");
    println!("reverse r = {:?}", "一二三四五六七八九十");    
    assert_eq!(r, "十九八七六五四三二一");
}