Problem 2 of the Euler project

p002.rs

struct Fibonacci {
    cur: i32,
    prev: i32,
}

//! Problem 2 of the Euler project

impl Iterator for Fibonacci {
    type Item = i32;
    
    fn next(&mut self) -> Option<Self::Item>{
        let ret = self.cur;
        self.cur = self.prev + self.cur;
        self.prev = ret;
        Some(ret)
    }
}

fn main() {
    let fib = Fibonacci{cur: 1, prev: 1};
    println!("{}", fib.take_while(|&x| x < 4000000)
    .filter(|x| x % 2 == 0).fold(0, |a,b| a + b));
}