oceanically moisted fizzbuzz

fizzbuzze.rs

type Predicates = std::collections::BTreeMap<Predicate, String>;

#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
struct Predicate(fn(u64) -> bool);

fn main() {
    let inputs = 0..=100;
    let mut predicates = Predicates::new();
    predicates.insert(Predicate(|v| v % 3 == 0), "Fizz".to_string());
    predicates.insert(Predicate(|v| v % 5 == 0), "Buzz".to_string());

    evaluate(inputs, predicates).for_each(|v| println!("{v}"));
}

fn evaluate(
    inputs: impl Iterator<Item = u64>,
    predicates: Predicates,
) -> impl Iterator<Item = String> {
    inputs.map(move |v| {
        predicates
            .iter()
            .filter_map(|(p, fv)| (p.0)(v).then_some(fv.to_owned()))
            .reduce(|a, b| format!("{a}{b}"))
            .unwrap_or(v.to_string())
    })
}