Primes in Rust

primes.rs

#[derive(Copy, Clone, Eq, PartialEq, Debug)]
enum Value {
    Unmarked,
    Marked
}

pub fn primes_up_to(n: usize) -> Vec<usize> {
    assert!(n>=2);
    let mut sieve = vec![Value::Unmarked; n];
    let mut p = 2;
    while p <= n {
        for i in (p..n).step_by(p).skip(1) {
            sieve[i] = Value::Marked;
        }
        loop {
            p+=1;
            if p >= n || sieve[p] == Value::Unmarked {
                break;
            }
        }
    }
    sieve.iter().enumerate().skip(2).filter(|(_, &v)| v==Value::Unmarked).map(|(i,_)|i).collect()
}

fn main(){
    dbg!(primes_up_to(100000000));
}