extern crate num_iter;

use num_iter::range_step;

pub fn sieve(n: u64) -> Vec<u64> {
    let mut prime_identifers: Vec<bool> = vec![true; n as usize + 1];
    let primes: Vec<u64> = vec![];

    for i in 2..(n as f64).sqrt() as usize + 1 {
        if *prime_identifers.get(i).unwrap() {
            for j in range_step(i.pow(2), n as usize + 1, i) {
                prime_identifers[j] = false;
            }
        }
    }

    prime_identifers.iter().skip(2).enumerate().fold(
        primes,
        |mut primes: Vec<u64>, (i, identifier)| {
            if *identifier {
                primes.push(i as u64 + 2);
            }
            primes
        },
    )
}