[Haskell-beginners] Folders and sub-folders

[Mike Houghton]

Cool, thanks.


> On 26 Feb 2016, at 13:01, Sylvain Henry <hsyl20 at gmail.com> wrote:
> 
> Your "isOk" function will filter out hidden directories on Unix (which may be what you want?).
> 
> Otherwise: isOk = (`notElem` [".",".."])
> 
> Also "\x -> folders x" = "folders"
> 
> 2016-02-26 11:42 GMT+01:00 Mike Houghton <mike_k_houghton at yahoo.co.uk <mailto:mike_k_houghton at yahoo.co.uk>>:
> Thanks.
> 
> 
> I sweated it  bit more and got
> 
> 
> 
> isOk FilePath -> Bool
> isOk  = not . isPrefixOf "."
> 
> folders :: FilePath -> IO [FilePath]
> folders fp  = do
>     all <- getDirectoryContents fp
>     z' <- filterM doesDirectoryExist $ map (fp </>) (filter isOk all)
>     x' <- mapM (\x -> folders x) z'
>     return $ z' ++ (concat x') ::
> 
> which seems to work.
> 
> 
> > On 25 Feb 2016, at 19:07, Imants Cekusins <imantc at gmail.com <mailto:imantc at gmail.com>> wrote:
> >
> > Hello Mike,
> >
> > below code find all files recursively from a starting point. It works.
> >
> > You'd need to tweak it to find folders instead.
> >
> >
> > import System.Directory
> > import Data.List
> >
> >
> > findAllFiles::FilePath -> IO [FilePath]
> > findAllFiles base0 = gd1 base0
> >>> = \list1 -> concatMap' recurse3 list1
> >     where gd1 d1 = filter f2 <$> (getDirectoryContents d1)
> >           f2 "." = False
> >           f2 ".." = False
> >           f2 _ = True
> >           recurse3 md3 = doesDirectoryExist md3full
> >>> = \isDir3 ->
> >                        if isDir3 then findAllFiles md3full
> >                        else pure [md3full]
> >                    where md3full = base0 ++ "/" ++ md3
> >
> >
> >
> > concatMap':: (a -> IO [b]) -> [a] -> IO [b]
> > concatMap' m0 list0 = sequence (m0 <$> list0)
> >>> = \list2 -> pure $ concat list2
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