(assign evalable-ld-printingp nil)

; Write a functon that puts a 23 after every
; element of list x.  E.g.,
; (twenty-three '(a b c d)) = (A 23 B 23 C 23 D 23)

; Alpha:  What's the right answer for the empty
; list?  The empty list, because there is no
; element to put a 23 after.

; Beta:  Suppose you have the right answer for
; (cdr x).  Then how do you transform it to the
; right answer for x?  You put a 23 after the
; (car x).

; Gamma: Here's the code:

(defun twenty-three (x)
  (if (endp x)
      nil
      (cons (car x)
            (cons 23
                  (twenty-three (cdr x))))))

(twenty-three '(a b c d))