fn insert_item<T>(start: &mut Option<Box<Item<T>>>, value: T, insert_before: fn(&Item<T>, &Item<T>) -> bool) where T: PartialEq + Display {
    println!("Creating item: {}", value);
    let mut item = Item::new(value);
    let mut current = &*start;
    let mut previous = &None;

    while current.is_some() && !insert_before(&item, current.as_ref().unwrap()) {
        previous = current;
        current = &current.as_ref().unwrap().next;
    }

    item.next = *current;
    let mut item = Some(Box::new(item));

    if previous.is_some() {
        previous.as_mut().unwrap().next = item
    }
    else {
        *start = item
    }
}