functional fizz buzz in emacs lisp

fizzbuzz.lisp

(defun divisible (a b)
  (equal 0 (% a b)))

(defun to_s (item) (format "%s" item))

(defun fizzbuzz (num)
  (let* ((fizz (if (divisible num 3) "fizz" ""))
        (buzz (if (divisible num 5) "buzz" ""))
        (combi (concat fizz buzz))
        (result (if (length> combi 0) combi (to_s num))))
    (message result)))

(mapcar 'fizzbuzz (number-sequence 1 50))