下面是Clojure的定义vector ：
(defn vector
"Creates a new vector containing the args."
{:added "1.0"
:static true}
([] [])
([a] [a])
([a b] [a b])
([a b c] [a b c])
([a b c d] [a b c d])
([a b c d & args]
(. clojure.lang.LazilyPersistentVector (create (cons a (cons b (cons c (cons d args))))))))
为什么有这么多的情况下？ 或者，如果有这么多，为什么没有更多？
我的猜测是，它引人注目的执行效率与概率之间的平衡，但我不太看不出这会更有效。
4似乎在效率的时候有很多的争论，当没有很多参数之间的平衡。
举个例子：
(defn vector-few
([] [])
([ & args ] (. clojure.lang.LazilyPersistentVector (create args))))
(defn vector-many
([] [])
([a] [a])
([a b] [a b])
([a b c] [a b c])
([a b c d] [a b c d])
([a b c d e] [a b c d e])
([a b c d e f] [a b c d e f])
([a b c d e f & args] (. clojure.lang.LazilyPersistentVector (create (cons a (cons b (cons c (cons d (cons e (cons f args))))))))))
运行具有4个元件的测试：
=> (time (dotimes [x 1000000] (vector 1 2 3 4)))
"Elapsed time: 12.082104 msecs"
=> (time (dotimes [x 1000000] (vector-few 1 2 3 4)))
"Elapsed time: 443.056339 msecs"
=> (time (dotimes [x 1000000] (vector-many 1 2 3 4)))
"Elapsed time: 11.812106 msecs"
然后用5：
=> (time (dotimes [x 1000000] (vector 1 2 3 4 5)))
"Elapsed time: 467.904979 msecs"
=> (time (dotimes [x 1000000] (vector-few 1 2 3 4 5)))
"Elapsed time: 537.080198 msecs"
=> (time (dotimes [x 1000000] (vector-many 1 2 3 4 5)))
"Elapsed time: 10.30695 msecs"
并用8（因此所有的功能都使用var-ARGS情况下）：
=> (time (dotimes [x 1000000] (vector 1 2 3 4 5 6 7 8)))
"Elapsed time: 832.803266 msecs"
=> (time (dotimes [x 1000000] (vector-few 1 2 3 4 5 6 7 8)))
"Elapsed time: 689.526288 msecs"
=> (time (dotimes [x 1000000] (vector-many 1 2 3 4 5 6 7 8)))
"Elapsed time: 905.95839 msecs"
