Rust fibonacci sequence

fib_seq.rs

use std::iter::Unfold;

fn main() {
    let fib_seq = Unfold::new((0i64, 1i64), |state| {
        // closures pretty much always borrow, so *dereference
        // to get value instead of pointer
        let (x, y) = *state;
        let result = Some(x);
        
        // again, set *value, not reference
        *state = (y, x + y);

        result
    });

    for n in fib_seq.take(10) {
        println!("{}", n);
    }
}