Can anyone explain me this function definition line of clojure
(defn insert [{:keys [el left right] :as tree} value]
(**something**))
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2 Answers
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)
2 Comments
Pankaj Manali
But why we have :keys here? Cant we just pass a deftype and use it
BWStearns
You could do that or you could also just pass a map, but if your data is just tree-like enough that you want to use this function and you don't want to make it into records then I'm pretty sure defining the function like this leaves it more generic/reusable.
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.
