Fetch primes using sieve, average values less than one million

sieve_avg_prime.rs

fn main() {
    let (cnt, sum) = sieve(1000000).iter()
        .fold((0u, 0u), |a, b| {
            let (cnt, sum) = a;
            (cnt + 1, sum + *b)
        });

    println!("{}", sum as f32 / cnt as f32);
}

fn sieve(max: uint) -> Vec<uint> {
    let mut values = Vec::from_fn(max, |_| true);
    for n in range(2, max) {
        if !values[n] {
            continue;
        } else {
            for i in range(2, max)
                .map(|un| un * n)
                .take_while(|un| *un < max) {
                values[i] = false;
            }
        }
    }

    values.iter().enumerate()
        .skip(2)
        .filter(|e| { let (_, prime) = *e; *prime })
        .map(|e| { let (value, _) = e; value })
        .collect()
}