It's chapter 11 exercise 11.22 d

(defun count-bases (dna)
(let ((dnaCnt '((A 0) (T 0) (G 0) (C 0))))
(labels ((count-element (x)
(incf (second (assoc x dnaCnt))))
(count-recurse (x)
(cond ((null x) t)
((atom (first x)) (and (count-element (first x))
(count-recurse (rest x))))
(t (and (count-recurse (first x))
(count-recurse (rest x)))))))
(count-recurse dna)
dnaCnt)))

The code is compiled without a problem.

When I run the program first time by evaluating

(count-bases '((g c) (a t) (t a) (t a) (c g)))

It gives the correct output:
((A 3) (T 3) (G 2) (C 2))

However, if I run it second time,

newLISP

(define (count-bases dna , (output '()))
(dolist (s (flat dna))
(ainc! output s))
output)

(count-bases '((g c) (a t) (t a) (t a) (c g)))
===>
((t 3) (a 3) (c 2) (g 2))

Given:

(macro (ainc! Alist Key Value Function Deflt)
(local (E-Message Val Func Def)
(setq Func Function)
(if (true? Func)
(setq Val Value)
(begin (setq Func +) (setq Val (or Value 1))))
(setq Def Deflt)
(if (= nil Def) (setq Def 0))
(unless
(catch
(setf (assoc Key Alist)
(list ($it 0) (Func Val ($it 1))))
'E-Message)
(if (starts-with E-Message "ERR: no reference")
(setf Alist (cons (list Key (Func Val Def)) Alist))
(throw-error E-Message)))))

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