Clojure - Example using optional args through named keys

gistfile1.clj

(defn my-math
  "Example using optional args through named keys."
  [nums & {:keys [operation]
           :or {operation +}}]
  (apply operation nums))

user=> (my-math '(1 2 3))
6
user=> (my-math '(1 2 3) :operation *)
6
user=> (my-math '(1 2 3) :operation /)
1/6
user=> (my-math '(1 2 3) :operation -)
-4

; Another approach using a nil argument and some clumsy validation.

(defn my-math2
  "Example using optional args through named keys."
  [nums & {:keys [operation]
           :or {operation nil}}]
  (let [op-fn (if (nil? operation) + operation)]
    (apply op-fn nums)))