test.clj

;; named arguments from the joy of clojure
;; the clojure version just feels not elegant, why?

;; clojure version
(defn slope
  [& {:keys [p1 p2] :or {p1 [0 0] p2 {1 1}}}]
  (float (/ (- (p2 1) (p1 1))
            (- (p2 0) (p1 0)))))

(slope :p1 [4 15] :p2 [3 21])

(slope [4 15] [3 21])

(slope)

;; python version
def slope(p1=(0,0), p2=(1,1)):
    return (float(p2[1] - p1[1])) / (p2[0] - p1[0])

slope((4,15), (3,21))

slope(p2=(2,1))

slope()

beautiful :)