use std::cell::Cell;

struct Neighbors<'a> {
    array: &'a [Cell<i32>],
    idx: std::ops::Range<usize>,
}

impl<'a> Neighbors<'a> {
    fn new(array: &'a [Cell<i32>]) -> Self {
        let idx = 1..array.len() - 1;
        Self { array, idx }
    }
}

impl<'a> Iterator for Neighbors<'a> {
    type Item = (&'a Cell<i32>, &'a Cell<i32>, &'a Cell<i32>);

    fn next(&mut self) -> Option<Self::Item> {
        let array = &self.array;
        self.idx.next().map(move |i| {
            let (a, b) = array.split_at(i);
            let (b, c) = b.split_at(1);

            let a = a.last().unwrap();
            let b = b.first().unwrap();
            let c = c.first().unwrap();

            (a, b, c)
        })
    }
}

fn main() {
    let array = [Cell::new(1), Cell::new(2), Cell::new(3), Cell::new(4), Cell::new(5)];
    for (a, b, c) in Neighbors::new(&array) {
        println!("{} -> {} <- {}", a.get(), b.get(), c.get());
    }
}