Hello Steve,
Monday, December 19, 2005, 10:42:19 PM, you wrote:
SH> What I'm after is something like:
SH> -- (psuedo-code)
SH> [(b,c,d) |
SH> b <- getDirectoryContents a_dir,
SH> c <- getDirectoryContents (a_dir ++ "/" ++ b),
SH> d <- getDirectoryContents (a_dir ++ "/" ++ b ++ "/" ++ c) ],
this can't work because IO itself a monad, so "IO [a]" is two monads,
and you can iterate only over external one, which is IO. instead:
let foreach = flip mapM
list <- foreach (getDirectoryContents a_dir) $ \b ->
foreach (getDirectoryContents (a_dir ++ "/" ++ b)) $ \c ->
foreach (getDirectoryContents (a_dir ++ "/" ++ b ++ "/" ++ c)) $ \d ->
return (b,c,d)
return $ concatMap $ concatMap list
SH> This function isn't so clear at a glance, and yet what it's doing
SH> seems like a pretty common thing to want to do: are there any library
SH> functions for monads (or IO in particular) that make this sort of thing
SH> easier, or should I to try and write my own function? Looks not too
SH> difficult to write but I think I might miss something important if I didn't
ask
SH> first... How would you do it?
if you just need to find all files recursively - use library
http://hackage.haskell.org/packages/FilePath-0.1.0.tgz to manipulate
filenames and function `doesDirectoryExist` to check that it is a
directory. don't forget that `getDirectoryContents` returns list what
contains names "." and ".."
--
Best regards,
Bulat mailto:[EMAIL PROTECTED]
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