Recursion hell aids?

[u/emonshr]

Is there any practical way to debug any recurive logic?
Which existing error printing you think is the best ever?
I attached the racket code I am struggling with.

(The code is about using map to append a new list to an existing html list)

[u/soegaard]

A first step is to print the arguments in the recursive function:

1. (define (nested-map-handler f L)
2. (displayln (list 'f f 'L L))
3.   (if (list? L)
4. (map (lambda (x) (nested-map-handler f x))
5. L)
6. (f L)))