fib.rs

#![feature(try_trait)]

// Fibonacci sequence takes last 2 numbers and sums them, but you can change as you like :)
const TAKE_COUNT: usize = 2;

fn main() {
    let mut vec: Vec<i64> = Vec::with_capacity(100);

    loop {
        let last = vec.iter().rev().take(TAKE_COUNT).collect::<Vec<_>>();

        match last
            .get(0..TAKE_COUNT)
            .or(Some(&[&1]))
            .and_then(|a| a.iter().try_fold(0 as i64, |acc, &x| acc.checked_add(*x)))
        {
            Some(add) => vec.push(add),
            _ => break, // If the checked_add overflowed
        }
    }

    println!("{:?}", vec);
}