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432 PurelyFunctional.tv Newsletter
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00 Atbash Cipher.md

Atbash Cipher

The Atbash Cipher is simple: replace every letter with its "mirror" in the alphabet. A is replaced by Z. B is replaced by Y. Etc. Write a function to calculate it.

Examples

(atbash "") ;=> ""
(atbash "hello") ;=> "svool"
(atbash "Clojure") ;=> "Xolqfiv"
(atbash "Yo!") ;=> "Bl!"

Please maintain capitalization and non-alphabetic characters.

Thanks to this site for the problem idea, where it is rated Very Hard in Python. The problem has been modified.

Please submit your solutions as comments on this gist.

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@KingCode
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KingCode commented Oct 7, 2021 •
edited 

(def mirror (let [lks "abcdefghijklmnopqrstuvwxyz", 
                  uks (clojure.string/upper-case lks)
                  lvs (reverse lks), 
                  uvs (reverse uks)]
              (-> (zipmap lks lvs)
                  (merge (zipmap uks uvs)))))

(defn atbash [msg]
  (->> msg
       (map #(get mirror % %))
       (apply str)))

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