Counting elements of a list and sublists

Question

I\'m trying to create a function to count all the elements in a list, including the elements of its sublists. initially, to get started, i came up with a basic function

Answer 1

Here is a recursive template you can use:

(define (num-atoms lst)
  (cond ((pair? lst) (+ (num-atoms ) 
                        (num-atoms )))
        ((null? lst) ) ; not an atom
        (else )))      ; an atom

This next example uses a helper that has the accumulated value (num) as an argument.

(define (num-atoms lst)
  ;; locally defined helper
  (define (helper num lst)
    (cond ((pair? lst) (helper (helper  ) )) ; recurse with the sum of elements from car
          ((null? lst) )          ; return accumulated value
          (else (helper  )))) ; recurse with add1 to num

  ;; procedure starts here
  (helper 0 lst))

Hope it helps