CODEWITHSUNDEEP
clojure
Pankaj Manali
Pankaj Manali

Reputation: 698

Clojure function explanation.

Can anyone explain me the stets of this clojure function

(defn to-list [{:keys [key left right] :as tree}]
  (when tree
    `(~@(to-list left) ~key ~@(to-list right))))

Upvotes: 1

Views: 79

Answers (1)

Ivaylo Petrov
Ivaylo Petrov

Reputation: 1172

So the to-list function expects a map that has some of three keys, namely key, left and right. This map can be accessed also by the name tree. See this for argument destructuring. Then you have a syntax quote (see this for details). It is roughly equivalent to 

(clojure.core/seq (clojure.core/concat (to-list left) 
                                       (clojure.core/list key) 
                                       (to-list rirght)))

So basically if you have nil for tree, it will return nil (which seems reasonable). If you have a tree with a key left (which is either nil or also a map possibly with keys key, left and right), then left tree is recursively printed, then the key is added, then if you have a key right, the right tree is printed recursively. If at any step you have only left or only right, the call (to-list left) will yield nil and the rest will work as already explained.

I hope this helps.

NOTE I don't have a clojure repl right now, so I did not test what is the exact equivalent of syntax-quote, but it should be very something similar to the thing that I wrote.

Upvotes: 2

Related Questions