How to implement an iterator of mutable references to the values in the right edges of a Binary Search Tree?

Question

I implemented a simple Binary Search Tree in Rust (following CIS 198, it\'s great), and for learning I\'m doing iterators that just run through the right edges.

I c

Answer 1

I think you cannot split self into 2 mutable objects (one for the Item, one for self itself) without using some unsafe code.

Answer 2

You need to change the type of the field IterMut::next to Option<&'a mut Node<T>>:

pub struct IterMut<'a, T: 'a> {
    next: Option<&'a mut Node<T>>,
}

impl<'a, T> Iterator for IterMut<'a, T> {
    type Item = &'a mut T;
    fn next(&mut self) -> Option<Self::Item> {
        self.next.take().map(|node| {
            self.next = node.right.0.as_mut().map(|node| &mut **node);
            &mut node.elem
        })

    }
}

You can find more useful information about the implementation of the mutable iterator for recursive data structures in the IterMut chapter of Learning Rust With Entirely Too Many Linked Lists.