; palindromep.l

(defun singletonp (l)
  (cond
    ((null l) nil)
    ((null (cdr l)) t)
    (t nil)
  )
)

(defun rac (l)
  (cond
    ((singletonp l) (car l))
    (t (rac (cdr l)))
  )
)

(defun rdc (l)
  (cond
    ((singletonp l) nil)
    (t (cons (car l) (rdc (cdr l))))
  )
)

(defun snoc (o l)
  (cond
    ((null l) (list o))
    (t (cons (car l) (snoc o (cdr l))))
  )
)

(defun palindromep (l)
  (cond
    ((null l) t)
    ((singletonp l) t)
    ((eq (car l) (rac l)) (palindromep (cdr (rdc l))))
    (t nil)
  )
)