clojure.core/cat

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Type: function Added: Clojure 1.7 Examples: 4 Runnable: 3

([rf])

A transducer which concatenates the contents of each input, which must be a collection, into the reduction.

Examples

by achesnais on 2016-05-10 ▶

;; cat is handy for untangling nested collections when using transducers (into [] (comp cat cat (map inc)) [[[1] [2]] [[3] [4]]]) ;; => [2 3 4 5]

by reborg on 2017-11-07 . May have evaluation errors. ▶

;; Remove the need of (mapcat identity coll) idiom: (def rota (sequence cat (repeat ["tom" "nick" "jane"]))) (nth rota 7) ; who's up next week? ;; nick ;; Although `cycle` would have done just fine here

by stanislas on 2021-08-26 ▶

;; combining map-indexed with cat for a "mapcat-indexed" (into [] (comp (map-indexed (fn [index val] (repeat index val))) cat) (range 5)) ;; => [1 2 2 3 3 3 4 4 4 4]

by ghoseb on 2022-08-05 ▶

;;; a concise and performant way to concat into a vector (into [] cat [[1 2 3] [4] [5 6 7]]) ;; => [1 2 3 4 5 6 7] (defn concatv "Concatenate `xs` and return the result as a vector." [& xs] (into [] cat xs)) (concatv '(1 2) [3] [4 5]) ;; => [1 2 3 4 5] ;;; this xducer form is equivalent to the `(vec (concat...` pattern (let [x [1 2 3] y 4 z [5 6 7]] (= (into [] cat [x [y] z]) (vec (concat x [y] z)))) ;; => true

See also

• clojure.core.reducers/cat
• clojure.core.reducers/foldcat (0)
• clojure.core/into (9)
• clojure.core/concat (7)

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