clojure.core/seque

View this page on ClojureDocs

Type: function Added: Clojure 1.0 Examples: 3 Runnable: 0

([s] [n-or-q s])

Creates a queued seq on another (presumably lazy) seq s. The queued seq will produce a concrete seq in the background, and can get up to n items ahead of the consumer. n-or-q can be an integer n buffer size, or an instance of java.util.concurrent BlockingQueue. Note that reading from a seque can block if the reader gets ahead of the producer.

Examples

by Chouser on 2010-08-28 . May have evaluation errors. ▶

(let [start (System/nanoTime) q (seque (iterate #(do (Thread/sleep 400) (inc %)) 0))] (println "sleep five seconds...") (Thread/sleep 5000) (doseq [i (take 20 q)] (println (int (/ (- (System/nanoTime) start) 1e7)) ":" i))) ;; The iterate form returns a lazy seq that delays nearly a half-second ;; before returning each subsequent item. Here seque starts a thread ;; generating the lazy seq. ;; The body of the let allows the seque thread to get ahead by five seconds ;; before it begins consuming the seq using doseq. The doseq prints a ;; timestamp and the value from the seq when it becomes available. The ;; first 11 or so are available almost instantly, until the consuming ;; doseq catches up with the producing iterate, at which point the consumer ;; blocks for 400ms before each item can be printed. ;;sleep five seconds... 500 : 0 500 : 1 500 : 2 500 : 3 500 : 4 500 : 5 500 : 6 500 : 7 500 : 8 500 : 9 500 : 10 500 : 11 520 : 12 560 : 13 600 : 14 640 : 15 680 : 16 720 : 17 760 : 18 800 : 19

by reborg on 2018-02-19 . May have evaluation errors. ▶

;; A relatively fast producer (a file filter) and a variable speed consumer ;; (because of pagination) are piped together. Use seque to enable search ahead ;; of "n" items assuming consumer will soon paginate. (defn search-files [q root n] (->> (java.io.File. root) file-seq (map (memfn getPath)) (filter #(re-find q %)) (seque n))) (defn paginate [n] (let [root (System/getProperty "user.home") search (search-files #"\.clj$" root 1000)] (loop [results (partition n search)] (println (with-out-str (clojure.pprint/write (first results)))) (println "more?") (when (= "y" (read-line)) (recur (rest results)))))) (paginate 3) ;; ("/Users/reborg/.atom/fixtures/bad.clj" ;; "/Users/reborg/.atom/fixtures/empty.clj" ;; "/Users/reborg/.atom/fixtures/good.clj") ;; more? ;; Note: seque is now producing 997 items ahead.

by sanel on 2025-04-28 . May have evaluation errors. ▶

;; seque can be used to force sequential processing of lazy seqs, especially ;; if you are dealing with chunking ;; Example without seque. It will always realize 32 elements, even if ;; we use only 10 elements down the pipeline. (->> (range 1 100) (map #(do (println "Loading" % "...") %)) (map #(do (println "Processing" % "...") %)) (take 10) (doall)) ;; Loading 1 ... ;; Loading 2 ... ;; Loading 3 ... ;; Loading 4 ... ;; Loading 5 ... ;; Loading 6 ... ;; Loading 7 ... ;; Loading 8 ... ;; Loading 9 ... ;; Loading 10 ... ;; Loading 11 ... ;; Loading 12 ... ;; Loading 13 ... ;; Loading 14 ... ;; Loading 15 ... ;; Loading 16 ... ;; Loading 17 ... ;; Loading 18 ... ;; Loading 19 ... ;; Loading 20 ... ;; Loading 21 ... ;; Loading 22 ... ;; Loading 23 ... ;; Loading 24 ... ;; Loading 25 ... ;; Loading 26 ... ;; Loading 27 ... ;; Loading 28 ... ;; Loading 29 ... ;; Loading 30 ... ;; Loading 31 ... ;; Loading 32 ... ;; Processing 1 ... ;; Processing 2 ... ;; Processing 3 ... ;; Processing 4 ... ;; Processing 5 ... ;; Processing 6 ... ;; Processing 7 ... ;; Processing 8 ... ;; Processing 9 ... ;; Processing 10 ... ;; Processing 11 ... ;; Processing 12 ... ;; Processing 13 ... ;; Processing 14 ... ;; Processing 15 ... ;; Processing 16 ... ;; Processing 17 ... ;; Processing 18 ... ;; Processing 19 ... ;; Processing 20 ... ;; Processing 21 ... ;; Processing 22 ... ;; Processing 23 ... ;; Processing 24 ... ;; Processing 25 ... ;; Processing 26 ... ;; Processing 27 ... ;; Processing 28 ... ;; Processing 29 ... ;; Processing 30 ... ;; Processing 31 ... ;; Processing 32 ... ;; (1 2 3 4 5 6 7 8 9 10) ;; Example with seque. It will correctly realize only 10 ;; elements and process them sequentially. (->> (range 1 100) (seque 10) ; n elements in queue, can be less (map #(do (println "Loading" % "...") %)) (map #(do (println "Processing" % "...") %)) (take 10) (doall)) ;; Loading 1 ... ;; Processing 1 ... ;; Loading 2 ... ;; Processing 2 ... ;; Loading 3 ... ;; Processing 3 ... ;; Loading 4 ... ;; Processing 4 ... ;; Loading 5 ... ;; Processing 5 ... ;; Loading 6 ... ;; Processing 6 ... ;; Loading 7 ... ;; Processing 7 ... ;; Loading 8 ... ;; Processing 8 ... ;; Loading 9 ... ;; Processing 9 ... ;; Loading 10 ... ;; Processing 10 ... ;; (1 2 3 4 5 6 7 8 9 10)

---

Content from the matching ClojureDocs page, with authors credited on each contribution.