September 2017 Update

Task/Caesar-cipher/Ruby/caesar-cipher.rb

@@ -1,27 +1,12 @@
-module CaesarCipher
-  AtoZ = (0..25).each_with_object({}) do |key,h|
-    str = [*"A".."Z"].rotate(key).join
-    h[key] = str + str.downcase
+class String
+  ALFABET = ("A".."Z").to_a
+
+  def caesar_cipher(num)
+    self.tr(ALFABET.join, ALFABET.rotate(num).join)
   end
 
-  def encrypt(key, plaintext)
-    (1..25) === key or raise ArgumentError, "key not in 1..25"
-    plaintext.tr(AtoZ[0], AtoZ[key])
-  end
-
-  def decrypt(key, ciphertext)
-    (1..25) === key or raise ArgumentError, "key not in 1..25"
-    ciphertext.tr(AtoZ[key], AtoZ[0])
-  end
 end
 
-include CaesarCipher
-
-original = "THEYBROKEOURCIPHEREVERYONECANREADTHIS"
-en = encrypt(3, original)
-de = decrypt(3, en)
-
-[original, en, de].each {|e| puts e}
-
-puts 'OK' if
-  (1..25).all? {|k| original == decrypt(k, encrypt(k, original))}
+#demo:
+encypted  = "THEYBROKEOURCIPHEREVERYONECANREADTHIS".caesar_cipher(3)
+decrypted = encypted.caesar_cipher(-3)