https://groups.google.com/forum/#!topic/clojure/RvHQPfBKJuM

something.clj

(defn- squared-edge-values
  [edges]
  (->> [:oc :oa :ob :ca :ab :bc]
       (map #(edges %1))
       (map #(* %1 %1))))

(defn- opposite-edge-values
  [edges]
  (let [[a2 b2 c2 d2 e2 f2] (squared-edge-values edges)]
    [[a2 e2 (+ a2 e2)]
     [b2 f2 (+ b2 f2)]
     [c2 d2 (+ c2 d2)]]))

(defn- closed-edge-values
  [edges]
  (let [[a2 b2 c2 d2 e2 f2] (squared-edge-values edges)]
    [[a2 b2 d2]
     [d2 e2 f2]
     [b2 c2 e2]
     [a2 c2 f2]]))

(defn- open-edge-values
  [edges]
  ;; implement later
  [[0 0 0]])

(defn- compute-edge-values
  [edge-fn edges]
  (->> edges
       (edge-fn)
       (map (fn [[x y z]] (* x y z)))
       (reduce +)))

(def ^:private add-opposite (partial compute-edge-values opposite-edge-values))
(def ^:private add-closed (partial compute-edge-values closed-edge-values))
(def ^:private add-open (partial compute-edge-values open-edge-values))

(defn volume 
  [{:keys [oa ob oc ab bc ca] :as edges}]
  {:pre [(every? #(number? %1) [oa ob oc ab bc ca])]}
  (let [opposite (add-opposite edges)
        closed (add-closed edges)
        open (add-open edges)]
    (Math/sqrt (* (- (- open closed) opposite) 0.5))))


(defn a-mod-input
  []
  (let [a 1.0]
    {:oc (* a (/ (Math/sqrt 6.0) 12.0))
     :oa (* a (/ (Math/sqrt 6.0) 4.0))
     :ob (* a (/ (Math/sqrt 2.0) 4.0))
     :ca (* a (/ (Math/sqrt 3.0) 3.0))
     :ab (/ a 2.0)
     :bc (* a (/ (Math/sqrt 3.0) 6.0))}))

(defn e-mod-input
  []
  (let [d 1.0
        r (/ d 2.0)
        h r]
    {:oc h
     :oa 1
     :ob 1
     :ca 1
     :ab 1
     :bc 1}))

(def a-mod-volume (volume (a-mod-input)))
(def e-mod-volume (volume (e-mod-input)))