cool_thing.rs

fn main() {
    let mut my_vec = vec![0, 1, 2, 3, 4, 5];
    let mut my_iter = MyIterator::new(&mut my_vec);

    // this prints out (0, 1), (1, 2), (2, 3), (3, 4), (4, 5), (5, None), None
    while let Some((ref mut left, ref mut right)) = my_iter.next() {
        println!("{:?}, {:?}", left, right);
    }
}

pub struct MyIterator<'vector, T> {
    data: &'vector mut [T],
    count: usize,
}

impl<'vector, T> MyIterator<'vector, T> {
    pub fn new(vec: &'vector mut Vec<T>) -> Self { 
        Self {
            data: vec,
            count: 0,
        }
    }

    #[allow(clippy::should_implement_trait)]
    pub fn next(&mut self) -> Option<(&mut T, Option<&mut T>)> {
        if self.count + 1 > self.data.len() {
            return None;
        }

        if self.data.len() == 1 {
            self.count += 1;
            return Some((self.data.first_mut().unwrap(), None));
        }

        let (left, right) = self.data.split_at_mut(self.count + 1);
        let first = left.last_mut();
        let second = right.first_mut();
        self.count += 1;

        Some((first.unwrap(), second))
    }
}