[sshine]

The article that explores these recursion schemes is: Functional Programming with Bananas, Lenses, Envelopes and Barbed Wire

https://maartenfokkinga.github.io/utwente/mmf91m.pdf

There is a review of this article, although it is quite readable in and of itself:

https://reasonablypolymorphic.com/blog/recursion-schemes/ind...