Code belonging to and explained in my "Bézier in Clojure" blog

bezier-in-clojure.clj

;;
;; Assume leiningen + lein-try plugin installed and working
;;
;; Fire up a repl with:
;;
;; lein try incanter "1.5.7"
;;

(require '[incanter.core   :as incanter])
(require '[incanter.charts :as charts])


(defn pow [base exponent]
  (reduce *' (repeat exponent base)))


(defn bezier-3 [P0 P1 P2]
  (fn [t]
    (+ 
      (* (pow (- 1 t) 2) P0)
      (* 2 (- 1 t) t     P1)
      (* (pow t 2)       P2))))


(defn view-bezier-plot [[x1 y1] [x2 y2] [x3 y3] plot-title]
  (let [b3x         (bezier-3 x1 x2 x3)
        xs          (map b3x (range 0 1.0 0.01))
        b3y         (bezier-3 y1 y2 y3)
        ys          (map b3y (range 0 1.0 0.01))
        dataset     (incanter/conj-cols xs ys)
        xy-plot     (charts/xy-plot "col-0" "col-1" :data dataset :points true :title plot-title)]
    (incanter/view xy-plot)))

;; Example bezier curves:

(view-bezier-plot [0 0] [1 0] [1 1] "increasing ascending")
(view-bezier-plot [0 0] [0 -1] [1 1] "swoosh")
(view-bezier-plot [-2 4] [0 -4] [2 4] "y = x^2 ?")
(view-bezier-plot [-1 0] [0 0] [1 0] "my pulse after a useless meeting")