#![allow(unused)]

extern crate num;

// prime sieve
pub fn prime_sieve(n: u64) -> Vec<u64> {
    let mut mask = vec![1; (n+1) as usize];
    mask[0] = 0;
    mask[1] = 0;
    let mut primes = vec![2];
    // mark off multiples of 2...
    let mut i=4_usize;
    while (i as u64) < n {
        mask[i] = 0;
        i += 2_usize;
    }
    // now parse the rest of the numbers...
    i = 3_usize;
    while (i as u64) < n {
        if mask[i] == 1 {
            // haven't seen this prime yet, so add it
            primes.push(i as u64);
            let mut j = i*i;
            // now cross off all multiples of i
            while (j as u64) < n {
                mask[j] = 0;
                j += i;
            }
        }
    }
    return primes;
}


fn main() {
    let primes = prime_sieve(100);
    println!("primes <= 100:");
    for p in primes {
        println!("{}", p);
    }

}