clojure.core/doseq

View this page on ClojureDocs

Type: macro Added: Clojure 1.0 Examples: 15 Runnable: 9

([seq-exprs & body])

Repeatedly executes body (presumably for side-effects) with bindings and filtering as provided by "for". Does not retain the head of the sequence. Returns nil.

Examples

by devijvers on 2010-07-22 ▶

;; Multiplies every x by every y. (doseq [x [-1 0 1] y [1 2 3]] (prn (* x y))) -1 ; x -1 y 1 -2 ; x -1 y 2 -3 ; x -1 y 3 0 ; x 0 y 1 0 ; x 0 y 2 0 ; x 0 y 3 1 ; x 1 y 1 2 ; x 1 y 2 3 ; x 1 y 3 nil ;; Notice that y is iterated over for every x. x could be seen as the 'outer' loop

by devijvers on 2010-07-22 . May have evaluation errors. ▶

(doseq [[x y] (map list [1 2 3] [1 2 3])] (prn (* x y))) 1 4 9 nil ;; where (map list [1 2 3] [1 2 3]) ((1 1) (2 2) (3 3))

by devijvers on 2010-07-22 . May have evaluation errors. ▶

(doseq [[[a b] [c d]] (map list (sorted-map :1 1 :2 2) (sorted-map :3 3 :4 4))] (prn (* b d))) 3 8 nil ;; where (map list (sorted-map :1 1 :2 2) (sorted-map :3 3 :4 4)) (([:1 1] [:3 3]) ([:2 2] [:4 4]))

by devijvers on 2010-07-22 . May have evaluation errors. ▶

(doseq [[k v] (map identity {:1 1 :2 2 :3 3})] (prn k v)) :1 1 :2 2 :3 3 nil ;; where (map identity {:1 1 :2 2 :3 3}) ([:1 1] [:2 2] [:3 3]) ;; or simply (doseq [[k v] {:1 1 :2 2 :3 3}] (prn k v)) :1 1 :3 3 :2 2 nil

by TimMc on 2011-02-16 ▶

;; Multiple sequences results in a Cartesian cross of their values. (doseq [a [1 2] b [3 4]] (println a b)) 1 3 1 4 2 3 2 4 nil

by cloojure on 2014-06-18 ▶

;; Keywords :let, :when, and :while are supported, the same as "for" (doseq [x (range 6) :when (odd? x) :let [y (* x x)] ] (println [x y]) ) [1 1] [3 9] [5 25] nil (doseq [x (range 99) :let [y (* x x)] :while (< y 30) ] (println [x y]) ) [0 0] [1 1] [2 4] [3 9] [4 16] [5 25] nil

by rezomegrelidze on 2015-04-01 . May have evaluation errors. ▶

;; ClojureCLR example ;; Prints names of running processes (doseq [x (System.Diagnostics.Process/GetProcesses)] (println (.get_ProcessName x))) avgnt SearchIndexer svchost chrome audiodg svchost mbamscheduler spoolsv nvxdsync avwebg7 GoogleCrashHandler64 svchost CCleaner64 ViakaraokeSrv ...

by justgage on 2015-04-30 ▶

;; simplest use (doseq [x [1 2 3 4 5]] (prn x)) 1 2 3 4 5 nil

by ibercode on 2017-11-13 . May have evaluation errors. ▶

;;looping over a collection ;;define CarMaker record (defrecord CarMaker [cm-name]) ;;define CarModel record (defrecord CarModel [model-name cmaker doors color]) ;;create a car-makes (def car-maker {"cm1" (->CarMaker "Renault")}) ;;createa models and add an CarMaker identifier to which model (def models { "m1" (->CarModel "Megane" "cm1" 3 "Black") "m2" (->CarModel "Zoe" "cm1" 5 "White") }) ;;println all model-name in the collection (doseq [[k v] models] (println (:model-name (get models k))))

by ibercode on 2017-11-17 ▶

;;doseq on vector (def my-vector [1 2 3 "a" "b" "c" :a :b :c]) (doseq [v my-vector] (println v)) ;;doseq on hash-map (def my-map {:a "A" :b "B" :c "C" :d 1 :e 2 :f 3}) (doseq [[k v] my-map] (println k "->" v))

by akhuramazda on 2019-01-05 ▶

(doseq [y (range 10)] (dotimes [z y] (print (inc z))) (newline)) 1 12 123 1234 12345 123456 1234567 12345678 123456789 nil

by nimitmaru on 2023-08-10 ▶

;; nothing will print (doseq [x [] y [1 2 3]] (prn x y)) ;; if any bindings have empty sequences, the body will never execute

by jimka2001 on 2024-02-01 ▶

;; to iterate across a map (doseq [[k v] {:a 1 :b 10 :c 100}] (println (list k v))) ;; outputs (:a 1) (:b 10) (:c 100) nil

by ReneGV on 2024-06-11 ▶

;; Iterate through a simple list (doseq [number [1 2 3 4]] (println number)) ;; Output 1 2 3 4 nil

by jimka2001 on 2024-06-30 . May have evaluation errors. ▶

;; The `:while` modifier triggers the inner-most loop to be aborted. ;; (to break out of the inner most loop). (doseq [a (range 5) b (range 5) :while (even? b) ;; when be fails to be even, then break out of b loop ] (println {:a a :b b}) ;; Output {:a 0, :b 0} {:a 1, :b 0} {:a 2, :b 0} {:a 3, :b 0} {:a 4, :b 0}

See also

• clojure.core/doall (0)
• clojure.core/dorun (1)
• clojure.core/for (14)
• clojure.core/dotimes (1)
• clojure.core/run! (1)

---

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