Add a generator for the sorted substitution table.

src/cipher_analytical_machine/ciphers/simple_substitution.clj

@@ -17,6 +17,13 @@
        (shuffled-numbers)
        (zipmap symbols)))
 
+(defn generate-sorted-substitution-table
+  "Generate the map (char, int) for the substittion. BUT a value is the index of a symbol (from 0)."
+  [symbols]
+  (-> (count symbols)
+      (take (range))
+      (zipmap symbols)))
+
 (defn find-value-in-table
   "It uses the substitution table to find the value of a char or a number."
   [char substitution-table]

test/cipher_analytical_machine/ciphers/simple_substitution_test.clj

@@ -22,6 +22,13 @@
         1 \a
         5 nil))))
 
+(deftest generate-sorted-substitution-table-test
+  (testing "If the symbol is in the table as a key, then the result won't nil."
+    (are [symbols expected-table]
+        (= expected-table (generate-sorted-substitution-table symbols))
+      "abc" {0 \a 1 \b 2 \c}
+      "a" {0 \a})))
+
 (deftest encrypt-message-test
   (let [symbols "abc"
         table {\a 1 \b 2 \c 3}]