My first 'real' Lisp program…

lottery.lisp

(defun lottery ()
  (flet ((shuffle (list)
    (let ((len (length list)))
      (loop repeat len
        do
          (rotatef
            (nth (random len) list)
            (nth (random len) list))
        finally
          (return list)))))
    (sort (subseq (shuffle (loop for i from 1 to 49 collect i)) 0 6) #'<)))

(lottery)
;; => (5 6 17 21 35 37)

;; here is a version with a better shuffle function. Note that the shuffle
;; function is written in a functional Lisp style. You need to read it from
;; inside to outside.
;; it uses a vector where the elements get a random double float attached.
;; The vector gets sorted by the random double floats.

;; the vector-iota function is another utility function

;; the 'domain' level LOTTERY function then is just a composition of the utility functions

(defun shuffle (v)
  (map-into v
            #'car
            (sort (map-into (make-array (length v))
                            (lambda (e)
                              (cons e (random 1.0d0)))
                            v)
                  #'<
                  :key #'cdr)))

(defun vector-iota (start end)
  "returns a vector with elements from start to end"
  (check-type start fixnum)
  (check-type end fixnum)
  (assert (>= end start) (start end))
  (let ((v (make-array (- end start -1))))
    (loop for i from start upto end do (setf (aref v (- i start)) i))
    v))

(defun lottery (&aux
                (start 1)
                (end 49))
  (sort (subseq (shuffle (vector-iota start end))
                0 6)
        #'<))

; Clojure
(take 6 (distinct (repeatedly #(inc (rand-int 49)))))