Question

I have:

(defun getTotalValue(pack)
  (cond ((null pack) 0)
    (t (+ (car (car pack)))) (getTotalValue (cdr pack))
  )
)

Which, to my understanding, will add up all the first elements of the items in a list. A test function call would be:

(getTotalValue '((10 c u) (3 s u) (5 h d) (7 s d) (12 h u)))

However, when I run the code above, it only prints out the first element of the first item in the list, 10. Why won’t it add up the first elements of all the items?

Answer 1

You had parenthesizing problem — two misplaced close parenthesis after (car (car pack)), so the cond expression terminates there and the recursion happens but the result is thrown away.

(defun getTotalValue (pack)
 (cond ((null pack) 0)
       (t (+ (car (car pack)) (getTotalValue (cdr pack))))))