Project Euler #3 in Rust

003.rs

struct PrimeStream {
	current: int
}

impl PrimeStream {
	fn new() -> PrimeStream {
		PrimeStream { current: 1 }
	}
}

impl Iterator<int> for PrimeStream {
	fn next(&mut self) -> Option<int> {
		self.current += 1;

		fn _is_prime(n: int) -> bool {
			let f = n as f32;
			let max = match f.sqrt().to_int() {
				Some(x) => x,
				None    => return false
			};

			if n % 2 == 0 {
				return false;
			}

			let mut multiple = 3;
			loop {
				if multiple >= max { break; }

				if n % multiple == 0 {
					return false;
				}

				multiple += 2;
			}

			return true;
		}

		while !_is_prime(self.current) {
			self.current += 1;
		}

		Some(self.current)
	}
}

fn main() {
	let mut largest = 0;
	let target = 600851475143;

	for n in PrimeStream::new().take_while(|n: &int| *n <= target) {
		if n % 10000 == 0 {
			println!("{}", n);
		}

		if target % n == 0 {
			largest = n;
			println!("New largest: {}", largest);
		}
	}

	println!("Final largest: {}", largest);
}