clojure.core/map-indexed

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Type: function Added: Clojure 1.2 Examples: 6 Runnable: 4

([f] [f coll])

Returns a lazy sequence consisting of the result of applying f to 0 and the first item of coll, followed by applying f to 1 and the second item in coll, etc, until coll is exhausted. Thus function f should accept 2 arguments, index and item. Returns a stateful transducer when no collection is provided.

Examples

by kredaxx on 2010-08-02 . May have evaluation errors. ▶

(map-indexed (fn [idx itm] [idx itm]) "foobar") ([0 \f] [1 \o] [2 \o] [3 \b] [4 \a] [5 \r])

by mmwaikar on 2011-12-19 . May have evaluation errors. ▶

;; or simply (map-indexed vector "foobar") ([0 \f] [1 \o] [2 \o] [3 \b] [4 \a] [5 \r])

by freetonik on 2018-10-29 ▶

(map-indexed hash-map "foobar") ;;=> ({0 \f} {1 \o} {2 \o} {3 \b} {4 \a} {5 \r})

by gluer on 2018-11-23 ▶

;; a simple example (map-indexed #(when (< % 2) (str % %2)) [:a :b :c]) ;;=> ("0:a" "1:b" nil) (keep-indexed #(when (< % 2) (str % %2)) [:a :b :c]) ;;=> ("0:a" "1:b")

by zackteo on 2020-08-04 ▶

;; Join the index and elements with list (map-indexed list [:a :b :c]) ;;=> ((0 :a) (1 :b) (2 :c))

by Crowbrammer on 2021-03-23 ▶

(= (map-indexed #(when (= 2 %2) [%1 "Hi"]) [1 1 2 2]) '(nil nil [2 "Hi"] [3 "Hi"])) ;;=>true

See also

• clojure.core/map (13)
• clojure.core/keep-indexed (5)

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