Haskell style head/tail functions in elisp

(defun square (n) (* n n))

(defun head-tail (&optional head &rest tail)
  (when head
    (insert (format "%d\n" (square head)))
    (apply #'head-tail tail)))


(defun head-tail (&optional head &rest tail)
  (when head
    (cons (square head) (apply #'head-tail tail))))


(head-tail 1 2 3 4 5)