Clojure Programming/Examples/API Examples/Hash-map tools
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get
[edit | edit source]user=> (get {:a 1, :b 2} :a)
1
;get also accepts an optional third argument,
;which is returned if key is not found in map:
user=> (get {:a 1, :b 2} :e 0)
0
;maps are functions of their keys, they delegate to get:
user=> ({:a 1, :b 2, :c 3} :a)
1
;and keys likewise
user=> (:b {:a 1, :b 2} 99)
2
assoc-in
[edit | edit source](def nested-structure { :level 0,
:nested1 { :level 1,
:nested2 { :level 2,
:final-data "initial data"}}})
user=> (assoc-in nested-structure [:nested1 :nested2 :final-data] "new data")
{:level 0, :nested1 {:nested2 {:level 2, :final-data "new data"}, :level 1}}
merge
[edit | edit source]Combine two maps into a more massive map
(merge {:a 1} {:b 2}) => {:a 1, :b 2})
(merge-with + {:a 1} {:a 2, :b 3}) => {:a 3 :b 3}