recursive list contents of a directory

RecursiveContents.hs

-- from Real World Haskell, Chapter 9

module RecursiveContents (getRecursiveContents) where

import Control.Monad (forM)
import System.Directory (doesDirectoryExist, getDirectoryContents, getCurrentDirectory)
import System.FilePath ((</>))

getRecursiveContents :: FilePath -> IO [FilePath]
getRecursiveContents topdir = do
	names <- getDirectoryContents topdir
	let properNames = filter (`notElem` [".", ".."]) names
	paths <- forM properNames $ \name -> do
		let path = topdir </> name
		isDirectory <- doesDirectoryExist path
		if isDirectory then getRecursiveContents path else return [path]
	return (concat paths)