clojure.core.reducers/foldcat

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Type: function Added: Clojure 1.5 Examples: 2 Runnable: 0

([coll])

Equivalent to (fold cat append! coll)

Examples

by reborg on 2017-11-10 . May have evaluation errors. ▶

;; Worth remembering that parallel fold in Clojure is enabled for: ;; vectors, maps and clojure.core.reducers.Cat objects. ;; r/foldcat returns a "Cat", so it can be parallel folded again: (r/fold + (r/foldcat (r/filter even? (r/foldcat (r/map inc (into [] (range 100000))))))) ;; 2500050000

by glts on 2018-04-01 . May have evaluation errors. ▶

;; One non-obvious thing about clojure.core.reducers/foldcat is its return type, ;; which is either clojure.core.reducers.Cat or java.util.ArrayList (!) ;; depending on the size of the source collection. (require '[clojure.core.reducers :as r]) (def small-vector (vec (range 10))) (def big-vector (vec (range 100000))) (type (r/foldcat (r/filter odd? small-vector))) ;;=> java.util.ArrayList (type (r/foldcat (r/filter odd? big-vector))) ;;=> clojure.core.reducers.Cat ;; Both return types are suited for further reduce-like processing, but they are ;; not general-purpose data types like proper Clojure collections.

See also

• clojure.core.reducers/fold (0)

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