RosettaCodeData/Task/Caesar-cipher/Eiffel/caesar-cipher.e

class
   APPLICATION

inherit
   ARGUMENTS

create
   make

feature {NONE} -- Initialization

   make
         -- Run application.
      local
         s: STRING_32
      do
         s := "The tiny tiger totally taunted the tall Till."
         print ("%NString to encode: " + s)
         print ("%NEncoded string: " + encode (s, 12))
         print ("%NDecoded string (after encoding and decoding): " + decode (encode (s, 12), 12))
      end

feature     -- Basic operations

   decode (to_be_decoded: STRING_32; offset: INTEGER): STRING_32
            -- Decode `to be decoded' according to `offset'.
      do
         Result := encode (to_be_decoded, 26 - offset)
      end

   encode (to_be_encoded: STRING_32; offset: INTEGER): STRING_32
            -- Encode `to be encoded' according to `offset'.
      local
         l_offset: INTEGER
         l_char_code: INTEGER
      do
         create Result.make_empty
         l_offset := (offset \\ 26) + 26
         across to_be_encoded as tbe loop
            if tbe.item.is_alpha then
               if tbe.item.is_upper then
                  l_char_code := ('A').code + (tbe.item.code - ('A').code + l_offset) \\ 26
                  Result.append_character (l_char_code.to_character_32)
               else
                  l_char_code := ('a').code + (tbe.item.code - ('a').code + l_offset) \\ 26
                  Result.append_character (l_char_code.to_character_32)
               end
            else
               Result.append_character (tbe.item)
            end
         end
      end
end