Clojureのvectorに対するlastは遅い

ので、vectorだとわかっている場合はpeekを使うといい

vector_peek.clj

(def s (doall (range 2000000)))
(def v (vec s))
(def l (apply list s))

(time (first s))
(time (first v))
(time (first l))
(time (last s))
(time (last v))
(time (last l))
(time (nth s (dec (count s))))
(time (nth v (dec (count v))))
(time (nth l (dec (count l))))
(time (get v (dec (count v))))
(time (peek v))

Elapsed time: 0.007123 msecs
Elapsed time: 0.005308 msecs
Elapsed time: 0.003352 msecs
Elapsed time: 191.406869 msecs
Elapsed time: 129.120391 msecs
Elapsed time: 77.368283 msecs
Elapsed time: 243.091859 msecs
Elapsed time: 0.006216 msecs
Elapsed time: 29.659985 msecs
Elapsed time: 0.093308 msecs
Elapsed time: 0.006775 msecs