(defparameter *input-vector* #(5 8 3 7 2))
(dct *input-vector*)
;; #(11.18034 2.176251 -1.2472882 0.51374316 -4.409566)
(idct *input-vector*)
;; #(11.576193 -0.61010736 1.6036125 1.8629377 -3.2522953)
For more details on the equation and the references, look into the doc folder.
MIT