Функция: найти количество троек подряд идущих одинаковых элементов списка

(defun count-triples (w)
  (cond ((null (cddr w)) 0)
        ((= (car w) (cadr w) (caddr w)) (1+ (count-triples (cdr w))))
        (t (count-triples (cdr w)))))
 
> (count-triples '(1 1 3 3 3 3 4 3 4 4 4 2 1 1 1))
4

(defun count-triples (w)
  (if (cddr w) (+ (if (= (car w) (cadr w) (caddr w)) 1 0)
                  (count-triples (cdr w)))
      0))
 
> (count-triples '(1 1 3 3 3 3 4 3 4 4 4 2 1 1 1))
4

(defun count-triples (w &optional (n 0))
  (if (cddr w)
      (count-triples (cdr w)
                     (+ n (if (= (car w) (cadr w) (caddr w)) 1 0)))
      n))
 
> (count-triples '(1 1 3 3 3 3 4 3 4 4 4 2 1 1 1))
4

(defun task (lst)
  (apply '+ (mapcar (lambda (x y z) (if (= x y z) 1 0)) lst (cdr lst) (cddr lst))))
 
==> TASK
 
(task '(1 1 3 3 3 3 4 3 4 4 4 2 1 1 1))
 
==> 4

(defun count-triples (w)
  (loop for a in w
        for b in (cdr w)
        for c in (cddr w)
        when (= a b c) count a))
 
> (count-triples '(1 1 3 3 3 3 4 3 4 4 4 2 1 1 1))
4