Caesar Cipher Example

cipher.hs

-- this is the original cipher function you will run                            
cipher [] _ = []
cipher a b = rot (head a) b : cipher (tail a) b

-- Take a look at this 'rotate' function.                                       
-- Rotate will convert a Char into another Char.                                
-- This almost works. But it doesn't loop around z-->a.                         
rotate :: Char -> Int -> Char
rotate c n = if n==0
             then c
             else rotate (succ c) (n-1)

-- This rotate code works much better!                                          
-- It loops around. y -> z -> a -> b -> ...                                     
-- Try calling this: rot 'z' 2                                                  
rot :: Char -> Int -> Char
rot c 0 = c
rot 'z' n = rot 'a' (n-1)
rot c n = rot (succ c) (n-1)