bionomial_choices.cl

; https://en.wikiversity.org/wiki/Binomial_coefficients

(defun arrangements (n k)
  (if (= n 0)
      (list nil)
       (append
         (when (< k n)
           (mapcar (lambda (tail)
                     (cons 0 tail))
                   (arrangements (- n 1) k)))
         (when (> k 0)
           (mapcar (lambda (tail)
                     (cons 1 tail))
                   (arrangements (- n 1) (- k 1))
                   )))))


(arrangements 4 3)