gistfile1.txt

(reduce
  (fn [acc v]
    (let [v' (dec v)]
      (if-not (and (even? v') (> v' 2))
        acc
        (+ acc v'))))
  0
  [1 2 3 4 5 6 7])
=> 10
(defn run-handwritten [] (reduce
                           (fn [acc v]
                             (let [v' (dec v)]
                               (if-not (and (even? v') (> v' 2))
                                 acc
                                 (+ acc v'))))
                           0
                           [1 2 3 4 5 6 7]))
=> #'user/run-handwritten
(def xform
  (comp
    (map dec)
    (filter even?)
    (filter #(> % 2))))
(defn run-transducer [] (transduce xform + [1 2 3 4 5 6 7]))
=> #'user/xform
=> #'user/run-transducer
(defn run-lazyseqs [] (->>
                        [1 2 3 4 5 6 7]
                        (map dec)
                        (filter even?)
                        (filter #(> % 2))
                        (reduce +)))
=> #'user/run-lazyseqs
(time (dotimes [_ (range 10000)] (run-handwritten)))
java.lang.ClassCastException: clojure.lang.LongRange cannot be cast to java.lang.Number
(time (dotimes [_ 10000] (run-handwritten)))
"Elapsed time: 12.271052 msecs"
=> nil
(time (dotimes [_ 1000000] (run-handwritten)))
"Elapsed time: 73.239849 msecs"
=> nil
(time (dotimes [_ 100000000] (run-handwritten)))
"Elapsed time: 6528.968932 msecs"
=> nil
(time (dotimes [_ 10000000] (run-handwritten)))
"Elapsed time: 650.94608 msecs"
=> nil
(time (dotimes [_ 10000000] (run-transducer)))
"Elapsed time: 1454.512474 msecs"
=> nil
(time (dotimes [_ 10000000] (run-lazyseqs)))
"Elapsed time: 7126.864204 msecs"