Return a string corresponding to the ordinal of the given integer using Rust's pattern matching

main.rs

fn main() {
    println!("Hello, world!");
}

pub fn ordinal(num: isize) -> String {
    let one = num % 10;
    let ten = (num / 10) % 10;

    match (one, ten) {
        (o, t) if t == 1 && o > 0 && 0 <= 3 => format!("{}th", num),
        (1, _) => format!("{}st", num),
        (2, _) => format!("{}nd", num),
        (3, _) => format!("{}rd", num),
        (_, _) => format!("{}th", num),
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test_ordinal() {
        assert_eq!("1st", ordinal(1));
        assert_eq!("2nd", ordinal(2));
        assert_eq!("3rd", ordinal(3));
        assert_eq!("4th", ordinal(4));
        assert_eq!("6th", ordinal(6));
        assert_eq!("7th", ordinal(7));
        assert_eq!("10th", ordinal(10));
        assert_eq!("11th", ordinal(11));
        assert_eq!("12th", ordinal(12));
        assert_eq!("13th", ordinal(13));
        assert_eq!("21st", ordinal(21));
        assert_eq!("22nd", ordinal(22));
        assert_eq!("23rd", ordinal(23));
        assert_eq!("111th", ordinal(111));
        assert_eq!("112th", ordinal(112));
        assert_eq!("913th", ordinal(913));
        assert_eq!("10012th", ordinal(10012));
    }
}