Peter Toth

> Here is one example API that I would love to implement with such a tree-node api: https://github.com/apache/datafusion/issues/10505 Thanks for sharing this @alamb. It's good to know that there are...

Let me close this PR as seemingly its open state causes some confusion. Feel free to use reuse the code if anyone wants to tacke this issue.

cc @alamb, @berkaysynnada, @ozankabak

> Thanks @peter-toth. After a quick look, I started thinking it might be better to use this new ref_visitor API instead of keeping also the original one. I'll take a...

@ozankabak, let me check the changes required for the alternative today or tomorrow and come back to you.

I'm still working on an alternative to this PR and will need a couple of more days to test a few different ideas...

> What do we think about merging this PR and filing a follow on ticket to unify the APIs? I'm ok with merging the current state of the PR. But...

I've rebased the PR on the latest `main`. The first commit is exactly the same as the previous state of this PR was, the second commit changes `TreeNode:apply()` and `TreeNode:visit()`...

Thanks all for the review! @alamb, those API example PRs look great!

> I think @peter-toth plans to break this PR up into smaller ones, so marking it as a draft to make it clear it isn't waiting on more feedback. If...