Obfuscate text for use in web pages

Obfuscate.hs

{-
Replaces each character with an HTML (or XML) escape code like " ". This is
useful as lightweight protection against email-address harvesting.

Example:
    ghci> obfuscate "a@example.co"
    "a@example.co"

Compare to the Clojure version: https://gist.github.com/bdesham/3327022
-}

module Obfuscate (obfuscate) where

import Data.Char (ord)
import Numeric (showHex)

numberAsHexString :: (Show a, Integral a) => a -> String
numberAsHexString n = showHex n ""

-- Just for kicks, we use hex numbers for some input characters and decimal
-- numbers for others
obfuscateChar :: Char -> String
obfuscateChar c
    | num `mod` 2 == 0 = "&#x" ++ numberAsHexString num ++ ";"
    | num `mod` 2 == 1 = "&#" ++ show num ++ ";"
    where num = ord c

obfuscate :: String -> String
obfuscate = concat . (map obfuscateChar)