You can do (something like; this is untested)
splitDirFile :: [FilePath] -> IO ([FilePath],[FilePath])
splitDirFile [] = return ([],[])
splitDirFile (f:fs) = do
(yess,nos) <- splitDirFile fs
exists <- doesDirectoryExist f
return $ if exists
then (f:yess,nos)
else (yess,f:nos)
You might also look at Control.Monad.filterM. I often define a
function "partitionM" which is like partition except it uses a monadic
test, just like you have.
Alex
On Tue, Jan 27, 2009 at 8:07 PM, Erik de Castro Lopo
Hi all,
I have a list of entries for a directory (FilePaths) and I'd like to partition them into files and directories using Data.List.partition:
partition :: [a] -> ([a], [a])
Now, one solution is to use unsafePerformIO:
splitDirFile :: [FilePath] -> ([FilePath], [FilePath]) splitDirFile paths = do partition (\p -> unsafePerformIO (doesDirectoryExist p)) paths
Two questions:
a) Is it possible to do this without invoking unsafePerformIO? Ie with a function signature of say:
partition :: [FilePath] -> IO ([FilePath], [FilePath])
b) Exactly how unsafe is the unsafePerformIO version?
Erik -- ----------------------------------------------------------------- Erik de Castro Lopo ----------------------------------------------------------------- The main confusion about C++ is that its practitioners think it is simultaneously a high and low level language when in reality it is good at neither. _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners