Reading in a binary file in haskell

How could I write a function with a definition something like...

readBinaryFile :: Filename -> IO Data.ByteString

I've got the functio开发者_如何学编程nal parts of Haskell down, but the type system and monads still make my head hurt. Can someone write and explain how that function works to me?

---

import Data.ByteString.Lazy
readFile fp

easy as pie man. Knock off the lazy if you don't want the string to be lazy.

import Data.ByteString.Lazy as BS
import Data.Word
import Data.Bits

fileToWordList :: String -> IO [Word8]
fileToWordList fp = do
    contents <- BS.readFile fp
    return $ unpack contents

---

readBinaryFile :: Filename -> IO Data.ByteString

This is simply the Data.ByteString.readFile function, which you should never have to write, since it is in the bytestring package.