clojure.core/concat

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Type: function Added: Clojure 1.0 Examples: 12 Runnable: 7

([] [x] [x y] [x y & zs])

Returns a lazy seq representing the concatenation of the elements in the supplied colls.

Examples

by kotarak on 2010-07-13 . May have evaluation errors. ▶

(concat [1 2] [3 4]) (1 2 3 4) (into [] (concat [1 2] [3 4])) [1 2 3 4] (concat [:a :b] nil [1 [2 3] 4]) (:a :b 1 [2 3] 4) => (concat [1] [2] '(3 4) [5 6 7] #{9 10 8}) (1 2 3 4 5 6 7 8 9 10) ;; The last three elements might appear in a different order.

by Bob Jarvis on 2014-02-12 . May have evaluation errors. ▶

(concat "abc" "def") (\a \b \c \d \e \f)

by prabhathk on 2015-05-04 . May have evaluation errors. ▶

(apply concat '(([1 2]) ([3 4] [5 6]) ([7 8]))) ([1 2] [3 4] [5 6] [7 8])

by RobinNagpal on 2017-08-04 ▶

(concat '(1 2 3) '(4 5 6)) ;; (1 2 3 4 5 6)

by RobinNagpal on 2017-08-04 ▶

(concat [1 2 3] [4 5 6]) ;; (1 2 3 4 5 6)

by RobinNagpal on 2017-08-04 ▶

(concat {:a "A" :b "B" :c "C"} {:d "D" :e "E"}) ;; ([:a "A"] [:b "B"] [:c "C"] [:d "D"] [:e "E"])

by reborg on 2018-03-07 ▶

(defn padding-right [s width pad] (apply str (take width (concat s (repeat pad))))) (padding-right "Clojure" 10 " ") ;; "Clojure "

by manojarya on 2019-09-26 ▶

;; beware! concat returns a lazy 'sequence'. (conj (concat [1 2] [3 4]) 5) ; doesn't return (1 2 3 4 5) ;;=>(5 1 2 3 4)

by jafingerhut on 2019-12-28 . May have evaluation errors. ▶

;; Here is a good article by Stuart Sierra in his "Clojure Dont's" series ;; on concat, and how using it in certain ways can lead to surprisingly large ;; stack usage: ;; https://stuartsierra.com/2015/04/26/clojure-donts-concat (first (reduce concat (map next-results (range 1 4000)))) ;; StackOverflowError clojure.core/seq (core.clj:133) (nth (iterate #(concat % [1 2 3]) [1 2 3]) 4000) ;; StackOverflowError clojure.core/seq (core.clj:133)

by themustafabasit on 2020-04-30 ▶

;; list 1 (def list1 (list 'let ['x 10])) ;; => #'user/list1 list1 ;; => (let [x 10]) ;; list 2 (def list2 (list '(println "x:" x) '(println "Bye!"))) ;; => #'user/list2 list2 ;; => ((println "x:" x) (println "Bye!")) ;; *** ;; concat all the elements of list1 & list2, and return a new list ;; In this case - let + [x 10] + (println "x:" x) + (println "Bye!") (concat list1 list2) ;; => (let [x 10] (println "x:" x) (println "Bye!")) (eval (concat list1 list2)) ;; => x: 10 ;; Bye! ;; nil ;; see also - quote

by wactbprot on 2021-02-05 ▶

(concat [1 2 3] nil) ;; => (1 2 3) (concat [1 2 3] [nil]) ;; => (1 2 3 nil)

by sofiiahitlan on 2025-02-20 . May have evaluation errors. ▶

(concat [1 2 3] 4 5) ;; => (1Error printing return value (IllegalArgumentException) at clojure.lang.RT/seqFrom (RT.java:577). ;; Don't know how to create ISeq from: java.lang.Long (concat [1 2 3] [4 5]) ;; => (1 2 3 4 5)

See also

• clojure.core/conj (9)
• clojure.core/into (9)
• clojure.core/lazy-cat (4)
• clojure.core/quote (1)
• clojure.core/mapcat (7)
• clojure.core/zipmap (7)
• clojure.core/cat (3)
• clojure.core.reducers/cat

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