🚧Immaturable skip list implement.

[LebranceBW]

Some basic fn, some test cases but document hasn't been written.
I'm not confident about the code. could you take a review 🔖 😄?

[weihanglo]

Overall looks great! Just need to be more ergonomic As a library user, the default constraint is way too limited. Also, the code could be more idiomatic, Rust provides lots of handy feature you can use without hardcoded or explicitly denoting.

In addition, have you ever tried implementing this with Rc? I think it might work to avoid any single line of unsafe Rust.

[LebranceBW]

@weihanglo Thank you very much for taking the time to review my code, 😃 and I'm sorry for my poor simple mistakes.

whereas, I have tried the implement the skiplist with Rc, but I'm trapped by the implement of iter just like the book. for example:

struct SkipNode<K, V> {
    entry: Entry<K, V>,
    next_by_height: [Option<Rc<RefCell<SkipNode>>>; MAX_HEIGHT],
}
impl<K, V> SkipNode<K, V> {
   pub fn iter() -> Iter<K, V> {
     ...//omittied
  }
}
pub struct Iter<'a, K, V>
{
    ptr: Option<Rc<RefCell<SkipNode<K, V>>>, // 1
    _marker: marker::PhantomData<&'a K>,
}
impl<'a, K, V: 'a> Iterator for Iter<'a, K, V>
{
    type Item =  std::cell::Ref('a, (K, V)); //2
    fn next(&mut self) -> Option<Self::Item> {
        self.ptr.map(|node| node.as_ref().borrow()); //3
    }
}

Because the RefCell holds the SkipNode, and the borrow() fn return a Ref. The code above will complain at 2 about return the temporary variable. I don't know how to overcome. Could you provide a solution? or tell me some other code just like this?