(defun digits (n)
  (labels
      ((f-iter (m acc)
         (cond ((= m 0) acc)
               ('t (f-iter (floor m 10)
                           (cons (mod m 10) acc))))))
    (f-iter n NIL)))

(defmacro sum (lst)
  `(reduce #'+ ,lst))

(sum (digits (expt 2 1000)))

— Me@2023-09-17 01:04:49 AM

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2023.09.17 Sunday (c) All rights reserved by ACHK