prime_generator.rs

// date: 2019-01-10
// license: GPLv3 https://www.gnu.org/licenses/gpl-3.0.txt
// author: nanpuyue <nanpuyue@gmail.com> https://blog.nanpuyue.com

#![feature(generators)]
#![feature(generator_trait)]

use std::ops::{Generator, GeneratorState};
use std::pin::Pin;

fn new_prime_generator() -> impl Generator<Yield = u8, Return = ()> {
    || {
        yield 2;
        yield 3;
        let mut list = vec![3];
        let mut last = 5u8;
        loop {
            for i in list.iter().copied() {
                let (q, r) = (last / i, last % i);
                if i > q {
                    list.push(last);
                    yield last;
                    break;
                }
                if r == 0 {
                    break;
                }
            }
            last = last.wrapping_add(2);
            if last == 1 {
                return;
            }
        }
    }
}

fn main() {
    let mut prime_generator = new_prime_generator();
    while let GeneratorState::Yielded(n) = Pin::new(&mut prime_generator).resume(()) {
        println!("{}", n);
    }
}