fizzbuzz in Common Lisp

fizzbuzz.lisp

;; Discovered via http://www.adampetersen.se/articles/fizzbuzz.htm
;; “Write a program that prints the numbers from 1 to 100. But for
;; multiples of three print “Fizz” instead of the number and for the
;; multiples of five print “Buzz”. For numbers which are multiples of
;; both three and five print “FizzBuzz”.”

(defun is-mult-p (n multiple)
  (= (rem n multiple) 0))

(defun fizzbuzz (&optional n)
  (let ((n (or n 1)))
    (if (> n 100)
        nil
        (progn
          (let ((mult-3 (is-mult-p n 3))
                (mult-5 (is-mult-p n 5)))
            (if mult-3
                (princ "Fizz"))
            (if mult-5
                (princ "Buzz"))
            (if (not (or mult-3 mult-5))
                (princ n))
            (princ #\linefeed)
            (fizzbuzz (+ n 1)))))))