module Text.AlphabetDistance (
      distance
    , norm
  ) where

import Data.Char (toLower)

rank :: Char -> Int
rank c = 1 + fromEnum (toLower c) - fromEnum 'a'

norm :: String -> Float
norm "" = 0
norm (c:cs) = (fromIntegral (rank c) + norm cs) / 27

distance :: String -> String -> Float
distance "" "" = 0
distance "" s = norm s
distance s "" = norm s
distance (ca:sa) (cb:sb) = (abs $ fromIntegral (rank ca - rank cb) + distance sa sb) / 27