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Clojure

Caesar Cipher (ROT13) in Clojure 1.0

*warn-on-reflection*

(ns caesar-cipher
 (:require (clojure.contrib [str-utils2 :as s]))
 (:use clojure.test ))

;; forward declaring just so I can order the functions how I want...
(declare
  rot13
  rot-msg
  rot-char
  in-range?
  rot-letter)

(defn rot13 "rot13 implementation"
  [msg] (rot-msg msg 13))

(defn rot-msg
  "Cipher a message via Caesar rotation.
     message - String to be encoded.
     i - factor by which to encode the message."
  [message i]
  (s/map-str #(rot-char % i) message))

(defn rot-char
  "applies caesar cipher to a single character. Only ciphers
   ascii a-z and A-Z, leaving other characters unchanged.
   c - a single ascii character.
   i - the factor by which to rotate the character."
  [c i] {:pre [(char? c) (number? i)]}
  (cond
    ;; cheating a bit here since the ascii-table won't change
    (in-range? c \A \Z) (rot-letter c i \A \Z \@)
    (in-range? c \a \z) (rot-letter c i \a \z \`)
    :default c))

(defn in-range? [c start end]
  (if (or (.equals c start) (.equals c end))
    true
    (let [compared-to-start (compare c start)
          compared-to-end (compare c end)]
      (or (= 0 compared-to-start)
          (= 0 compared-to-end)
          (and (pos? compared-to-start) (neg? compared-to-end))))))

(defn rot-letter [c i start end start-minus-1]
  (let [rotated-char (char (+ (int c) i))]
    (if (in-range? rotated-char start end)
      rotated-char
      (let [overflow (- (int rotated-char) (int end))]
        (char (+ (int start-minus-1) overflow))))))


;; Some tests - TODO: learn about Clojure unit tests...

(defn test-rot13 []
  (let [message "a MeSsAgE"
        encoded (rot13 message)]
    (is (= message (rot13 encoded)))))

(defn do-all-rotations [msg]
  (loop [i 0]
      (if (= i 26)
        (println "done")
        (do
          (println (rot-msg msg i))
          (recur (inc i))))))

(defn rotate-alphabet []
  (let [uppercase-alphabet "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
        lowercase-alphabet "abcdefghijklmnopqrstuvwxyz"]
    (do
      (do-all-rotations uppercase-alphabet)
      (do-all-rotations lowercase-alphabet))))
https://snipt.net/embed/5155ef37dc3acb56b049dc4b506ae4ba/
/raw/5155ef37dc3acb56b049dc4b506ae4ba/
5155ef37dc3acb56b049dc4b506ae4ba
clojure
Clojure
74
2019-06-17T05:05:52
True
False
False
/api/public/snipt/19673/
caesar-cipher-rot13-in-clojure-10
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><a href="#L-1"> 1</a> <a href="#L-2"> 2</a> <a href="#L-3"> 3</a> <a href="#L-4"> 4</a> <a href="#L-5"> 5</a> <a href="#L-6"> 6</a> <a href="#L-7"> 7</a> <a href="#L-8"> 8</a> <a href="#L-9"> 9</a> <a href="#L-10">10</a> <a href="#L-11">11</a> <a href="#L-12">12</a> <a href="#L-13">13</a> <a href="#L-14">14</a> <a href="#L-15">15</a> <a href="#L-16">16</a> <a href="#L-17">17</a> <a href="#L-18">18</a> <a href="#L-19">19</a> <a href="#L-20">20</a> <a href="#L-21">21</a> <a href="#L-22">22</a> <a href="#L-23">23</a> <a href="#L-24">24</a> <a href="#L-25">25</a> <a href="#L-26">26</a> <a href="#L-27">27</a> <a href="#L-28">28</a> <a href="#L-29">29</a> <a href="#L-30">30</a> <a href="#L-31">31</a> <a href="#L-32">32</a> <a href="#L-33">33</a> <a href="#L-34">34</a> <a href="#L-35">35</a> <a href="#L-36">36</a> <a href="#L-37">37</a> <a href="#L-38">38</a> <a href="#L-39">39</a> <a href="#L-40">40</a> <a href="#L-41">41</a> <a href="#L-42">42</a> <a href="#L-43">43</a> <a href="#L-44">44</a> <a href="#L-45">45</a> <a href="#L-46">46</a> <a href="#L-47">47</a> <a href="#L-48">48</a> <a href="#L-49">49</a> <a href="#L-50">50</a> <a href="#L-51">51</a> <a href="#L-52">52</a> <a href="#L-53">53</a> <a href="#L-54">54</a> <a href="#L-55">55</a> <a href="#L-56">56</a> <a href="#L-57">57</a> <a href="#L-58">58</a> <a href="#L-59">59</a> <a href="#L-60">60</a> <a href="#L-61">61</a> <a href="#L-62">62</a> <a href="#L-63">63</a> <a href="#L-64">64</a> <a href="#L-65">65</a> <a href="#L-66">66</a> <a href="#L-67">67</a> <a href="#L-68">68</a> <a href="#L-69">69</a> <a href="#L-70">70</a> <a href="#L-71">71</a> <a href="#L-72">72</a> <a href="#L-73">73</a> <a href="#L-74">74</a></pre></div></td><td class="code"><div class="highlight"><pre><span></span><span id="L-1"><a name="L-1"></a><span class="nv">*warn-on-reflection*</span> </span><span id="L-2"><a name="L-2"></a> </span><span id="L-3"><a name="L-3"></a><span class="p">(</span><span class="kd">ns </span><span class="nv">caesar-cipher</span> </span><span id="L-4"><a name="L-4"></a> <span class="p">(</span><span class="ss">:require</span> <span class="p">(</span><span class="nf">clojure.contrib</span> <span class="p">[</span><span class="nv">str-utils2</span> <span class="ss">:as</span> <span class="nv">s</span><span class="p">]))</span> </span><span id="L-5"><a name="L-5"></a> <span class="p">(</span><span class="ss">:use</span> <span class="nv">clojure.test</span> <span class="p">))</span> </span><span id="L-6"><a name="L-6"></a> </span><span id="L-7"><a name="L-7"></a><span class="c1">;; forward declaring just so I can order the functions how I want...</span> </span><span id="L-8"><a name="L-8"></a><span class="p">(</span><span class="nf">declare</span> </span><span id="L-9"><a name="L-9"></a> <span class="nv">rot13</span> </span><span id="L-10"><a name="L-10"></a> <span class="nv">rot-msg</span> </span><span id="L-11"><a name="L-11"></a> <span class="nv">rot-char</span> </span><span id="L-12"><a name="L-12"></a> <span class="nv">in-range?</span> </span><span id="L-13"><a name="L-13"></a> <span class="nv">rot-letter</span><span class="p">)</span> </span><span id="L-14"><a name="L-14"></a> </span><span id="L-15"><a name="L-15"></a><span class="p">(</span><span class="kd">defn </span><span class="nv">rot13</span> <span class="s">&quot;rot13 implementation&quot;</span> </span><span id="L-16"><a name="L-16"></a> <span class="p">[</span><span class="nv">msg</span><span class="p">]</span> <span class="p">(</span><span class="nf">rot-msg</span> <span class="nv">msg</span> <span class="mi">13</span><span class="p">))</span> </span><span id="L-17"><a name="L-17"></a> </span><span id="L-18"><a name="L-18"></a><span class="p">(</span><span class="kd">defn </span><span class="nv">rot-msg</span> </span><span id="L-19"><a name="L-19"></a> <span class="s">&quot;Cipher a message via Caesar rotation.</span> </span><span id="L-20"><a name="L-20"></a><span class="s"> message - String to be encoded.</span> </span><span id="L-21"><a name="L-21"></a><span class="s"> i - factor by which to encode the message.&quot;</span> </span><span id="L-22"><a name="L-22"></a> <span class="p">[</span><span class="nv">message</span> <span class="nv">i</span><span class="p">]</span> </span><span id="L-23"><a name="L-23"></a> <span class="p">(</span><span class="nf">s/map-str</span> <span class="o">#</span><span class="p">(</span><span class="nf">rot-char</span> <span class="nv">%</span> <span class="nv">i</span><span class="p">)</span> <span class="nv">message</span><span class="p">))</span> </span><span id="L-24"><a name="L-24"></a> </span><span id="L-25"><a name="L-25"></a><span class="p">(</span><span class="kd">defn </span><span class="nv">rot-char</span> </span><span id="L-26"><a name="L-26"></a> <span class="s">&quot;applies caesar cipher to a single character. Only ciphers</span> </span><span id="L-27"><a name="L-27"></a><span class="s"> ascii a-z and A-Z, leaving other characters unchanged.</span> </span><span id="L-28"><a name="L-28"></a><span class="s"> c - a single ascii character.</span> </span><span id="L-29"><a name="L-29"></a><span class="s"> i - the factor by which to rotate the character.&quot;</span> </span><span id="L-30"><a name="L-30"></a> <span class="p">[</span><span class="nv">c</span> <span class="nv">i</span><span class="p">]</span> <span class="p">{</span><span class="ss">:pre</span> <span class="p">[(</span><span class="nf">char?</span> <span class="nv">c</span><span class="p">)</span> <span class="p">(</span><span class="nf">number?</span> <span class="nv">i</span><span class="p">)]}</span> </span><span id="L-31"><a name="L-31"></a> <span class="p">(</span><span class="nf">cond</span> </span><span id="L-32"><a name="L-32"></a> <span class="c1">;; cheating a bit here since the ascii-table won&#39;t change</span> </span><span id="L-33"><a name="L-33"></a> <span class="p">(</span><span class="nf">in-range?</span> <span class="nv">c</span> <span class="sc">\A</span> <span class="sc">\Z</span><span class="p">)</span> <span class="p">(</span><span class="nf">rot-letter</span> <span class="nv">c</span> <span class="nv">i</span> <span class="sc">\A</span> <span class="sc">\Z</span> <span class="sc">\@</span><span class="p">)</span> </span><span id="L-34"><a name="L-34"></a> <span class="p">(</span><span class="nf">in-range?</span> <span class="nv">c</span> <span class="sc">\a</span> <span class="sc">\z</span><span class="p">)</span> <span class="p">(</span><span class="nf">rot-letter</span> <span class="nv">c</span> <span class="nv">i</span> <span class="sc">\a</span> <span class="sc">\z</span> <span class="sc">\`</span><span class="p">)</span> </span><span id="L-35"><a name="L-35"></a> <span class="ss">:default</span> <span class="nv">c</span><span class="p">))</span> </span><span id="L-36"><a name="L-36"></a> </span><span id="L-37"><a name="L-37"></a><span class="p">(</span><span class="kd">defn </span><span class="nv">in-range?</span> <span class="p">[</span><span class="nv">c</span> <span class="nv">start</span> <span class="nv">end</span><span class="p">]</span> </span><span id="L-38"><a name="L-38"></a> <span class="p">(</span><span class="k">if </span><span class="p">(</span><span class="nb">or </span><span class="p">(</span><span class="nf">.equals</span> <span class="nv">c</span> <span class="nv">start</span><span class="p">)</span> <span class="p">(</span><span class="nf">.equals</span> <span class="nv">c</span> <span class="nv">end</span><span class="p">))</span> </span><span id="L-39"><a name="L-39"></a> <span class="nv">true</span> </span><span id="L-40"><a name="L-40"></a> <span class="p">(</span><span class="k">let </span><span class="p">[</span><span class="nv">compared-to-start</span> <span class="p">(</span><span class="nf">compare</span> <span class="nv">c</span> <span class="nv">start</span><span class="p">)</span> </span><span id="L-41"><a name="L-41"></a> <span class="nv">compared-to-end</span> <span class="p">(</span><span class="nf">compare</span> <span class="nv">c</span> <span class="nv">end</span><span class="p">)]</span> </span><span id="L-42"><a name="L-42"></a> <span class="p">(</span><span class="nb">or </span><span class="p">(</span><span class="nb">= </span><span class="mi">0</span> <span class="nv">compared-to-start</span><span class="p">)</span> </span><span id="L-43"><a name="L-43"></a> <span class="p">(</span><span class="nb">= </span><span class="mi">0</span> <span class="nv">compared-to-end</span><span class="p">)</span> </span><span id="L-44"><a name="L-44"></a> <span class="p">(</span><span class="nb">and </span><span class="p">(</span><span class="nb">pos? </span><span class="nv">compared-to-start</span><span class="p">)</span> <span class="p">(</span><span class="nb">neg? </span><span class="nv">compared-to-end</span><span class="p">))))))</span> </span><span id="L-45"><a name="L-45"></a> </span><span id="L-46"><a name="L-46"></a><span class="p">(</span><span class="kd">defn </span><span class="nv">rot-letter</span> <span class="p">[</span><span class="nv">c</span> <span class="nv">i</span> <span class="nv">start</span> <span class="nv">end</span> <span class="nv">start-minus-1</span><span class="p">]</span> </span><span id="L-47"><a name="L-47"></a> <span class="p">(</span><span class="k">let </span><span class="p">[</span><span class="nv">rotated-char</span> <span class="p">(</span><span class="nb">char </span><span class="p">(</span><span class="nb">+ </span><span class="p">(</span><span class="nb">int </span><span class="nv">c</span><span class="p">)</span> <span class="nv">i</span><span class="p">))]</span> </span><span id="L-48"><a name="L-48"></a> <span class="p">(</span><span class="k">if </span><span class="p">(</span><span class="nf">in-range?</span> <span class="nv">rotated-char</span> <span class="nv">start</span> <span class="nv">end</span><span class="p">)</span> </span><span id="L-49"><a name="L-49"></a> <span class="nv">rotated-char</span> </span><span id="L-50"><a name="L-50"></a> <span class="p">(</span><span class="k">let </span><span class="p">[</span><span class="nv">overflow</span> <span class="p">(</span><span class="nb">- </span><span class="p">(</span><span class="nb">int </span><span class="nv">rotated-char</span><span class="p">)</span> <span class="p">(</span><span class="nb">int </span><span class="nv">end</span><span class="p">))]</span> </span><span id="L-51"><a name="L-51"></a> <span class="p">(</span><span class="nb">char </span><span class="p">(</span><span class="nb">+ </span><span class="p">(</span><span class="nb">int </span><span class="nv">start-minus-1</span><span class="p">)</span> <span class="nv">overflow</span><span class="p">))))))</span> </span><span id="L-52"><a name="L-52"></a> </span><span id="L-53"><a name="L-53"></a> </span><span id="L-54"><a name="L-54"></a><span class="c1">;; Some tests - TODO: learn about Clojure unit tests...</span> </span><span id="L-55"><a name="L-55"></a> </span><span id="L-56"><a name="L-56"></a><span class="p">(</span><span class="kd">defn </span><span class="nv">test-rot13</span> <span class="p">[]</span> </span><span id="L-57"><a name="L-57"></a> <span class="p">(</span><span class="k">let </span><span class="p">[</span><span class="nv">message</span> <span class="s">&quot;a MeSsAgE&quot;</span> </span><span id="L-58"><a name="L-58"></a> <span class="nv">encoded</span> <span class="p">(</span><span class="nf">rot13</span> <span class="nv">message</span><span class="p">)]</span> </span><span id="L-59"><a name="L-59"></a> <span class="p">(</span><span class="nf">is</span> <span class="p">(</span><span class="nb">= </span><span class="nv">message</span> <span class="p">(</span><span class="nf">rot13</span> <span class="nv">encoded</span><span class="p">)))))</span> </span><span id="L-60"><a name="L-60"></a> </span><span id="L-61"><a name="L-61"></a><span class="p">(</span><span class="kd">defn </span><span class="nv">do-all-rotations</span> <span class="p">[</span><span class="nv">msg</span><span class="p">]</span> </span><span id="L-62"><a name="L-62"></a> <span class="p">(</span><span class="k">loop </span><span class="p">[</span><span class="nv">i</span> <span class="mi">0</span><span class="p">]</span> </span><span id="L-63"><a name="L-63"></a> <span class="p">(</span><span class="k">if </span><span class="p">(</span><span class="nb">= </span><span class="nv">i</span> <span class="mi">26</span><span class="p">)</span> </span><span id="L-64"><a name="L-64"></a> <span class="p">(</span><span class="nb">println </span><span class="s">&quot;done&quot;</span><span class="p">)</span> </span><span id="L-65"><a name="L-65"></a> <span class="p">(</span><span class="nf">do</span> </span><span id="L-66"><a name="L-66"></a> <span class="p">(</span><span class="nb">println </span><span class="p">(</span><span class="nf">rot-msg</span> <span class="nv">msg</span> <span class="nv">i</span><span class="p">))</span> </span><span id="L-67"><a name="L-67"></a> <span class="p">(</span><span class="nf">recur</span> <span class="p">(</span><span class="nb">inc </span><span class="nv">i</span><span class="p">))))))</span> </span><span id="L-68"><a name="L-68"></a> </span><span id="L-69"><a name="L-69"></a><span class="p">(</span><span class="kd">defn </span><span class="nv">rotate-alphabet</span> <span class="p">[]</span> </span><span id="L-70"><a name="L-70"></a> <span class="p">(</span><span class="k">let </span><span class="p">[</span><span class="nv">uppercase-alphabet</span> <span class="s">&quot;ABCDEFGHIJKLMNOPQRSTUVWXYZ&quot;</span> </span><span id="L-71"><a name="L-71"></a> <span class="nv">lowercase-alphabet</span> <span class="s">&quot;abcdefghijklmnopqrstuvwxyz&quot;</span><span class="p">]</span> </span><span id="L-72"><a name="L-72"></a> <span class="p">(</span><span class="nf">do</span> </span><span id="L-73"><a name="L-73"></a> <span class="p">(</span><span class="nf">do-all-rotations</span> <span class="nv">uppercase-alphabet</span><span class="p">)</span> </span><span id="L-74"><a name="L-74"></a> <span class="p">(</span><span class="nf">do-all-rotations</span> <span class="nv">lowercase-alphabet</span><span class="p">))))</span> </span></pre></div> </td></tr></table>
clojure, rot13