CODEWITHSUNDEEP
clojure
rbb
rbb

Reputation: 999

Clojure - Applying a Function to a vector of vectors

I have a vector [[[1 2] [3 4]] [[5 6] [7 8]] [9 10] 11]. I want to apply a function to this vector but keep the data structure.

For example I want to add 1 to every number but keep the data structure to get the result being [[[2 3] [4 5]] [[6 7] [8 9]] [10 11] 12]. Is this possible?

I have tried 

(map #(+ 1 %) (flatten [[[1 2] [3 4]] [[5 6] [7 8]] [9 10] 11]))
=> (2 3 4 5 6 7 8 9 10 11 12)

But you can see that the data structure is not the same.

Is there maybe a function that takes (2 3 4 5 6 7 8 9 10 11 12) to [[[2 3] [4 5]] [[6 7] [8 9]] [10 11] 12]

I thought maybe to use postwalk but I'm not sure if this is correct.

Any help would be much appreciated

Upvotes: 5

Views: 444

Answers (3)

user2609980
user2609980

Reputation: 10474

Another way to solve your problem is via Specter. You do need another dependency then, but it can be a helpful library.

(ns your-ns.core
  (:require [com.rpl.specter :as specter]))

(def data [[[1 2] [3 4]] [[5 6] [7 8]] [9 10] 11])

(specter/defprotocolpath TreeWalker) ;; define path walker
(specter/extend-protocolpath TreeWalker
                             ;; stop walking on leafs (in this case long)
                             Object nil
                             ;; when we are dealing with a vector, TreeWalk all elements
                             clojure.lang.PersistentVector [specter/ALL TreeWalker])

You can extend it to perform more complicated operations. For this use case normal Clojure is good enough.

(specter/transform [TreeWalker] inc data)
;; => [[[2 3] [4 5]] [[6 7] [8 9]] [10 11] 12]

Upvotes: 0

leetwinski
leetwinski

Reputation: 17859

also the classic recursive solution is not much more difficult:

(defn inc-rec [data]
  (mapv #((if (vector? %) inc-rec inc) %) data))
#'user/inc-rec

user> (inc-rec [1 [2 3 [4 5] [6 7]] [[8 9] 10]])
;;=> [2 [3 4 [5 6] [7 8]] [[9 10] 11]]

Upvotes: 4

Lee
Lee

Reputation: 144116

You can use postwalk:

(require '[clojure.walk :as walk])

(let [t [[[1 2] [3 4]] [[5 6] [7 8]] [9 10] 11]]
  (walk/postwalk (fn [x] (if (number? x) (inc x) x)) t))

Upvotes: 6

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