Rust bounded worker pool over item chunks

use std::thread;

fn pool<F>(items: Vec<u32>, workers: usize, f: F) -> Vec<Result<u32, String>>
where
    F: Fn(u32) -> Result<u32, String> + Sync,
{
    let workers = workers.max(1).min(items.len().max(1));
    let chunk = ((items.len() + workers - 1) / workers).max(1);
    let mut out = Vec::new();
    thread::scope(|s| {
        let mut handles = Vec::new();
        for part in items.chunks(chunk) {
            let f = &f;
            handles.push(s.spawn(move || part.iter().map(|&x| f(x)).collect::<Vec<_>>()));
        }
        for handle in handles {
            out.extend(handle.join().unwrap());
        }
    });
    out
}