Skip to content

Instantly share code, notes, and snippets.

@xfbs xfbs/prime.rs
Created Jan 17, 2018

Embed
What would you like to do?
rust prime generator
use std::vec::Vec;
pub struct Prime {
list: Vec<u64>
}
impl Prime {
pub fn new() -> Self {
Prime {
list: vec![2, 3]
}
}
fn next(&mut self) -> u64 {
let mut last = self.list.last().unwrap() + 2;
while !self.is_prime(last) {
last += 2;
}
self.list.push(last);
last
}
pub fn is_prime(&self, num: u64) -> bool {
let root = (num as f64).sqrt() as u64;
for prime in self.list.iter() {
if *prime > root {
return true;
}
if (num % *prime) == 0 {
return false;
}
}
true
}
pub fn nth(&mut self, n: usize) -> u64 {
while self.list.len() < n {
self.next();
}
self.list[n-1]
}
}
pub struct PrimeIter<'a> {
prime: &'a Prime,
pos: usize
}
impl<'a> Iterator for PrimeIter<'a> {
type Item = u64;
fn next(&mut self) -> Option<Self::Item> {
self.pos += 1;
Some(self.prime.nth(self.pos - 1))
}
}
impl<'a> IntoIterator for Prime {
type Item = u64;
type IntoIter = PrimeIter<'a>;
fn into_iter(self) -> Self::IntoIter {
PrimeIter {
prime: &self,
pos: 0
}
}
}
#[test]
fn test_prime_next() {
let mut p = Prime::new();
assert!(p.next() == 5);
assert!(p.next() == 7);
assert!(p.next() == 11);
assert!(p.next() == 13);
assert!(p.next() == 17);
assert!(p.next() == 19);
assert!(p.next() == 23);
assert!(p.next() == 29);
assert!(p.next() == 31);
}
#[test]
fn test_prime_nth() {
let mut p = Prime::new();
assert!(p.nth(1) == 2);
assert!(p.nth(2) == 3);
assert!(p.nth(3) == 5);
assert!(p.nth(4) == 7);
assert!(p.nth(5) == 11);
assert!(p.nth(6) == 13);
assert!(p.nth(7) == 17);
assert!(p.nth(8) == 19);
assert!(p.nth(9) == 23);
assert!(p.nth(10) == 29);
assert!(p.nth(11) == 31);
assert!(p.nth(12) == 37);
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.