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Adding augmented maps to a vector based on regex text grabbing

Submitted by: @import:stackexchange-codereview··
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mapstextaugmentedaddinggrabbingbasedregexvector

Problem

This is my latest brain child for clojure, could it be done with less code, cleaner, or in a more re applicable way? I am at a pretty early stage in my clojure learning so an in depth explanation of how and why my code is faulty would help me get a handle on what I am doing wrong so I do not build bad habits.

(def next-apendage
  #(hash-map :name (clojure.string/replace (:name %1) #"[0-9]" (str (+ 1 %2 (read-string (re-find #"[0-9]" (:name %1))))))))

(defn add-apendages
  [times part]
  (loop [done 0
         final-apendages [part]]
    (if (= done times)
      final-apendages
      (recur
       (inc done)
       (conj final-apendages
             (next-apendage part done))))))

(add-apendages 2 {:name "tentacle-3"}) 
;;OUTPUT->[{:name "tentacle-3"} {:name "tentacle-4"} {:name "tentacle-5"}]


That really ugly looking first function takes two arguments a map and a number. The number is added (with a compensation for done starting at 0) to the :name string of the map. The second function condenses the new appendages along side the original into a list. The third section is a call to the second function.

Solution

Some things that stand out from your code:

  • (def next-appendage #()) is really (defn next-appendage [part done])



  • Do not use anonymous functions except for really really short functions. You next-appendage function is long for Clojure standards.



  • Instead of hash-map you can use the map literal directly {:name (clojure.string/replace ,,,}



  • Even though it seems cool when you are starting Clojure, one liners are very hard to read. You already know that is "really ugly" :)



  • It is unusual to use loop. Most of the time you can replace it with a simpler map` or similar



  • Do not use read-string, unless you know what you are doing



My version would look like:

(defn add-apendages [times part]
  (let [ ;; find the prefix and initial number
        [_ prefix number-str] (first (re-seq #"(.*)-([0-9]+)$" (:name part)))
         ;; parse the number, using Java interop
        initial-number (Integer/parseInt number-str)]
    ;; Build the list of results using a simple map operation
    (map (fn [n] {:name (str prefix "-" n)})
         (range initial-number (+ 1 initial-number times)))))

Code Snippets

(defn add-apendages [times part]
  (let [ ;; find the prefix and initial number
        [_ prefix number-str] (first (re-seq #"(.*)-([0-9]+)$" (:name part)))
         ;; parse the number, using Java interop
        initial-number (Integer/parseInt number-str)]
    ;; Build the list of results using a simple map operation
    (map (fn [n] {:name (str prefix "-" n)})
         (range initial-number (+ 1 initial-number times)))))

Context

StackExchange Code Review Q#121621, answer score: 3

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