The first problem in the OP is ill-typed, so if this was intended to help people get a good grasp on recursion, that may be counterproductive. I never had any

The first problem in the OP is ill-typed, so if this was intended to help people get a good grasp on recursion, that may be counterproductive. I never had any problem using recursion, but my ability to reason about it at an abstract level is due in large part to the excellent paper "Functional Programming with Bananas, Lenses, Envelopes and Barbed Wire", which covers various abstract approaches to dealing with recursion schemes. https://maartenfokkinga.github.io/utwente/mmf91m.pdf https://maartenfokkinga.github.io/utwente/mmf91m.pdf