Strip your spaces!

gistfile1.hs

import System.Environment
import System.IO
import System.Directory
import Data.String.Utils
import Control.Monad


main = do places <- getArgs
          let place = if places == [] 
                      then ["."]
                      else places

          every place (map_dir_tree (act_on_file make_clean) 
                                    (endswith ".rb"))
     where every = flip mapM_

map_dir_tree action predicate path =
  do file <- getDirectoryContents path
  
     for (every file (not . startswith ".")) $ 
       \file ->  do let fullPath = path ++ "/" ++ file
    
                    exists <- doesDirectoryExist fullPath
              
                    if exists
                    then dir_tree_map_ action predicate fullPath
                    else 
                         when (predicate fullPath) 
                              (action    fullPath)

     where for   = flip mapM_
           every = flip filter

act_on_file action file =
  do content <- readFile file
     
     force_reading content
     
     packed <- action content file

     writeFile file packed

force_reading = (`seq` return ()) . length

make_clean content file = do let packed = clean_teh content

                             when (packed /= content) 
                                  (putStrLn (file ++ "!"))

                             return packed

clean_teh content = let cleared = map rstrip `on` lines content
                    in  unlines cleared

on = ($)