fn main() {
    let src = 12;
    let result = is_even(src);
    println!("{src} is even? {result}");
}

fn is_even(n: u32) -> bool {
    match n {
        0 => true,
        1 => false,
        _ => is_odd(n - 1),
    }
}

fn is_odd(n: u32) -> bool {
    match n {
        0 => false,
        1 => true,
        _ => is_even(n - 1),
    }
}

#[cfg(test)]
mod tests {
    use crate::{is_even, is_odd};

    #[test]
    fn it_works() {
        let src = 12;
        let result = is_even(src);
        assert!(result);
    }

    #[test]
    fn it_works_again() {
        let src = 5;
        let result = is_odd(src);
        assert!(result);
    }
}