すごいH本読書会 in 大阪#4

main-todo.hs

import Parupunte
import Prelude hiding ((+), (*))
import qualified Prelude as Pre

main = do
     print $ (2+8)*(3+7) -- should print 37

Parupunte.hs

module Parupunte
( (+)
, (*)
) where

import qualified Prelude as Pre


(+) a b = b Pre.* a
(*) a b = b Pre.+ a

Rot13.hs

module Toys.Rot13
(encrypt
) where

import Data.Char

encrypt :: String -> String
encrypt = map (rot13)

rot13 c
    | not $ isAlpha c = c
    | rot > max = chr $ rot - 26
    | otherwise = chr rot 
    where rot = ord c + 13
          max = ord z
          z = if (isUpper c) then 'Z' else 'z'