alphabet kata

alphabet kata

import Data.Char

char_to_pos c = ord c - ord 'a'
pos_to_char p = chr (p `mod` 26 + ord('a')) 

transcode_letter op key text = pos_to_char (text_offset `op` key_offset + 26)
    where [key_offset, text_offset] = map char_to_pos [key, text]

encode_letter = transcode_letter (+)
decode_letter = transcode_letter (-)

transcode_string f key = map (uncurry f) . zip (cycle key)

encode_string = transcode_string encode_letter
decode_string = transcode_string decode_letter