CODEWITHSUNDEEP
clojure
Pankaj Manali
Pankaj Manali

Reputation: 698

Function definition in clojure

Can anyone explain me this function definition line of clojure

 (defn insert [{:keys [el left right] :as tree} value] 
      (**something**))

Upvotes: 1

Views: 126

Answers (2)

MicSokoli
MicSokoli

Reputation: 841

This is argument destructuring in Clojure. You can read more about it here: https://gist.github.com/john2x/e1dca953548bfdfb9844

{:keys [el left right]} assumes the first argument (we'll call it arg) is a map and binds (:el arg) to el, (:left arg) to left and (:right arg) to right for the scope of the function.

{:keys [.. .. ..]} :as tree} binds arg to tree.

Then value is handled normally, without any desctructuring.

Upvotes: 2

Nicolas Modrzyk
Nicolas Modrzyk

Reputation: 14187

The insert function is using destructuring for maps, retrieving values from keys. I think the below would make this clearer:

(defn insert [{:keys [el left right] :as tree} value]
      (println (str el " " left " " right))
      (println "-")
      (println tree)
      (println "-")
      (println value)   )


(def mytree  {:el "el" :left "left" :right "right"})

(insert mytree 3)

Upvotes: 3

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