raindrops (macros).rs

macro_rules! raindrop {
    ($func:ident, $factor:expr, $text:expr) => {
        fn $func<'a>(n: u32) -> Option<&'a str> {
            if n % $factor == 0 {
                return Some($text);
            }
            return None;
        }
    };
}

raindrop!(is_factor_of_three, 3, "Pling");
raindrop!(is_factor_of_five, 5, "Plang");
raindrop!(is_factor_of_seven, 7, "Plong");

pub fn raindrops(n: u32) -> String {
    let mut result = String::new();

    if let Some(v) = is_factor_of_three(n) {
        result.push_str(v);
    }

    if let Some(v) = is_factor_of_five(n) {
        result.push_str(v);
    }

    if let Some(v) = is_factor_of_seven(n) {
        result.push_str(v);
    }

    if result.is_empty() {
        result.push_str(&n.to_string())
    }

    return result;
}