clojure.core/hash-map

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Type: function Added: Clojure 1.0 Examples: 6 Runnable: 3

([] [& keyvals])

keyval => key val Returns a new hash map with supplied mappings. If any keys are equal, they are handled as if by repeated uses of assoc.

Examples

by zmila on 2010-07-28 . May have evaluation errors. ▶

;; create hash map the long way (hash-map) {} ;; create array map the short way {} {} ;; sending a key more times, will remap it to the last value (hash-map :key1 1, :key1 2) {:key1 2} {:key1 1, :key1 2} IllegalArgumentException Duplicate key: :key1 clojure.lang.PersistentArrayMap.createWithCheck (PersistentArrayMap.java:70) (hash-map :key1 'val1, 'key2 :val2, [:compound :key] nil) {[:compound :key] nil, :key1 val1, key2 :val2}

by zmila on 2010-07-28 . May have evaluation errors. ▶

(map #(hash-map % 0) (seq "abcdefgh")) ({\a 0} {\b 0} {\c 0} {\d 0} {\e 0} {\f 0} {\g 0} {\h 0}) (apply hash-map (.split "a 1 b 2 c 3" " ")) {"a" "1", "b" "2", "c" "3"}

by dipto_sarkar on 2012-07-05 . May have evaluation errors. ▶

; a hash map can be stored in a var by using `def` (def person {:name "Steve" :age 24 :salary 7886 :company "Acme"}) #'user/person person {:age 24, :name "Steve", :salary 7886, :company "Acme"}

by octopusgrabbus on 2012-07-21 ▶

;; Take a sequence of sequences (vector of vectors), and create a map ;; using date as the map key. (def csv1 [["01/01/2012" 1 2 3 4]["06/15/2012" 38 24 101]]) (map #(hash-map (keyword (first %1)) (vec (rest %1))) csv1) ;;=> ({:01/01/2012 [1 2 3 4]} {:06/15/2012 [38 24 101]}) ;; merge the list of maps into a single map (apply merge '({"01/01/2012" [1 2 3 4]} {"06/15/2012" [38 24 101]})) ;;=> {"06/15/2012" [38 24 101], "01/01/2012" [1 2 3 4]}

by smnplk on 2016-03-26 ▶

(apply hash-map [:a 1 :b 2]) ;;=> {:b 2 :a 1} ;;is the same as (def build-map (partial assoc {})) (apply build-map [:a 1 :b 2]) ;;=> {:b 2 :a 1}

by rebcabin on 2019-07-19 ▶

;; A hash map acts like a lookup function taking a key as first argument: ({:a 1, :b 2} :a) ;;=> 1 ;; If the key is not present, nil is returned... ({:a 1, :b 2} :qwerty) ;;=> nil ;; ... unless there is a second argument, which becomes the default value to ;; return when the lookup key is not found: ({:a 1, :b 2} :qwerty :uiop) ;;=> :uiop ;; That behavior can lead to surprises: (let [map-example {:a 1, :b 2}] (map-example #(* % %) (range 10))) ;;=> (0 1 2 3 4 5 6 7 8 9) ;; since (range 10) is the default and #(* % %) is an anonymous function that isn't a key in map-example ;; It may be more explicit to use get instead (get {:a 1, :b 2} :qwerty :uiop) ;;=> :uiop

Note by er2

If you want to create a map from a sequence of pairs, e.g. [[k1 v1] [k2 v2]], see into.

See also

• clojure.core/merge (8)
• clojure.core/assoc (8)
• clojure.core/dissoc (3)
• clojure.core/array-map (3)
• clojure.core/sorted-map (5)
• clojure.core/into (9)
• clojure.core/zipmap (7)
• clojure.core/keys (2)
• clojure.core/vals (1)

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