我查看了 Maps 的源代码,它基本上一直在创建惰性序列。我原本认为迭代集合并添加到瞬态向量会更快,但显然不是这样。我对 Clojure 的性能行为有什么误解?
;=> (time (do-with / (range 1 1000) (range 1 1000)))
;"Elapsed time: 23.1808 msecs"
;
; vs
;=> (time (doall (map #(/ %1 %2) (range 1 1000) (range 1 1000))))
;"Elapsed time: 2.604174 msecs"
(defn do-with
[fn coll1 coll2]
(let [end (count coll1)]
(loop [i 0
res (transient [])]
(if
(= i end)
(persistent! res)
(let [x (nth coll1 i)
y (nth coll2 i)
r (fn x y)]
(recur (inc i) (conj! res r)))
))))