clojure.core/rseq

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Type: function Added: Clojure 1.0 Examples: 4 Runnable: 2

([rev])

Returns, in constant time, a seq of the items in rev (which can be a vector or sorted-map), in reverse order. If rev is empty returns nil

Examples

by pkolloch on 2010-08-20 ▶

(vec (range 10)) [0 1 2 3 4 5 6 7 8 9] (rseq (vec (range 10))) (9 8 7 6 5 4 3 2 1 0)

by clojureking on 2014-08-29 ▶

(rseq (into (sorted-map) {:a 1 :b 2})) ;; => ([:b 2] [:a 1])

by Crowbrammer on 2021-02-19 . May have evaluation errors. ▶

;; Huge performance boost for vectors and sorted maps over `reverse`. (def nums (vec (range 1000000))) (time (reverse nums)) ;; "Elapsed time: 30.1222 msecs" (time (rseq nums)) ;; "Elapsed time: 0.0664 msecs"

by tomdl89 on 2023-03-30 . May have evaluation errors. ▶

;; The docstring doesn't mention sorted-sets directly ;; Arguably they are implied by mention of sorted-maps (def ss (into (sorted-set) (range 1e6))) ;; So this is a constant time way of getting the last element: (time (first (rseq ss))) "Elapsed time: 0.04606 msecs" ;; => 999999 ;; vs the linear approach: (time (last ss)) "Elapsed time: 164.557625 msecs" ;; => 999999

See also

• clojure.core/reverse (2)

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