some fibonacci sequence fns using fold

fibo.rs

fn main() {
    fn fibo_fancy(val: i32) -> i32 {
        if val == 0 {
            return 0
        }
        (1..=val)
            .fold((None, None), |acc, curr| {
                let (m1, m2) = acc;
                if curr <= 2 {
                    match (m1, m2) {
                        (None, Some(m)) => (Some(m), Some(1)),
                        (Some(m), None) => (Some(m), Some(1)),
                        (None, None) => (None, Some(1),),
                        _ => unreachable!(),
                    }
                } else {
                    match (m1, m2) {
                        (Some(m1), Some(m2)) => {
                            let tmp = m1 + m2;
                            (Some(m2), Some(tmp))
                        }
                        _ => unreachable!(),
                    }
                }
            })
            .1
            .unwrap()
    }

    assert_eq!(fibo_fancy(0), 0);
    assert_eq!(fibo_fancy(1), 1);
    assert_eq!(fibo_fancy(2), 1);
    assert_eq!(fibo_fancy(3), 2);
    assert_eq!(fibo_fancy(4), 3);
    assert_eq!(fibo_fancy(5), 5);

    assert_eq!(fibo_fancy(29), 514229);
}

fibo_num.rs

fn main() {
    fn fibo_fancy(val: i32) -> i32 {
        if val == 0 {
            return 0
        }
        (1..=val)
            .fold((0, 0), |acc, curr| {
                let (m1, m2) = acc;
                if curr <= 2 {
                    match (m1, m2) {
                        (0, 0) => (0, 1),
                        (0, num) => (num, 1),
                        (num, 0) => (num, 1),
                        _ => unreachable!(),
                    }
                } else {
                    let tmp = m1 + m2;
                    (m2, tmp)
                }
            })
            .1
    }

    assert_eq!(fibo_fancy(0), 0);
    assert_eq!(fibo_fancy(1), 1);
    assert_eq!(fibo_fancy(2), 1);
    assert_eq!(fibo_fancy(3), 2);
    assert_eq!(fibo_fancy(4), 3);
    assert_eq!(fibo_fancy(5), 5);

    assert_eq!(fibo_fancy(29), 514229);
}