Binary tree inorder traversal, using path to root and left subtrees in Haskell

Alternative implementation of binary tree inorder traversal index function, using path to root and left subtrees of path nodes with R direction in Haskell

code: https://gist.github.com/evgenii-malov/cca0c241e3df9a46776eddf1f57e84a0

Paths with directions - https://www.youtube.com/watch?v=jCAG76JKIkY ... https://www.youtube.com/watch?v=pIrRiF63ta8