[Haskell-cafe] Re: Suggested additions to System.FilePath.Posix/Windows

[Neil Mitchell]

Hi Marcus,

Thanks for your suggestions. I'm a Windows user so aren't really
qualified to comment on these suggestions - it depends what Posix
users would like. I suggest you follow the Library Submission Process
- filepath is now a core library, and as such I don't have the
freedom/power to change it as I like, and it's generally something
lots of people should think about.

http://www.haskell.org/haskellwiki/Library_submissions

Thanks

Neil

PS. I'm off for 3 weeks starting very soon, so will be unlikely to
reply to any email thread for a long time :-)


On Thu, Sep 17, 2009 at 10:58 AM, Marcus D. Gabriel <marcus at gabriel.name> wrote:
> Hello Neil
>
> I used System.FilePath.Posix quite extensively recently, and I thank
> you for the package filepath.  There were however two words that I
> needed which I could not construct from those in
> System.FilePath.Posix.  They are maybe of interest to you and others.
>
> I submit these two words to you for consideration for inclusion in
> System.FilePath.Posix.  Please change the names as you see fit.
>
> I do not know if they make sense for System.FilePath.Windows.  If
> the do not make sense, then please feel free to drop them so as to
> preserve the interface.
>
> As requested, I Cc'ed the haskell-cafe, but I am not at the moment
> following these threads, so if anyone else responds, please Cc me
> if you wish.
>
> Thanks again and cheers,
> - Marcus
>
> P.S. Here they are.  Although I use ksh(1) as an example, this is a
> feature of POSIX shells.
>
>> -- | 'reduceFilePath' returns a pathname that is reduced to canonical
>> -- form equivalent to that of ksh(1), that is, symbolic link names are
>> -- treated literally when finding the directory name.  See @cd -L@ of
>> -- ksh(1).  Specifically, extraneous separators @(\"/\")@, dot
>> -- @(\".\")@, and double-dot @(\"..\")@ directories are removed.
>>
>> reduceFilePath :: FilePath -> FilePath
>> reduceFilePath = joinPath . filePathComponents
>
> This is in turn built on filePathComponents that does all the work.
>
>> filePathComponents :: FilePath -> [FilePath]
>> filePathComponents ""     = []
>> filePathComponents (c:cs) =
>>     reverse $ snd $ foldl accumulate
>>                           (if c == pathSeparator then ([],["/"]) else
>> ([c],[]))
>>                           (cs++[pathSeparator])
>>     where
>>     accumulate :: (String,[String]) -> Char -> (String,[String])
>>     accumulate (cs, css) c =
>>         if c == pathSeparator
>>         then ([],(if null cs then id else cons cs) css)
>>         else (cs++[c],css)
>>     cons :: String -> [String] -> [String]
>>     cons cs css
>>         | cs == "." = css
>>         | cs /= ".." || null css = cs : css
>>         | otherwise =
>>           let hd = head css
>>               tl = tail css
>>           in if hd == [pathSeparator]
>>              then css
>>              else if hd == ".."
>>                   then cs : css
>>                   else if null tl
>>                        then ["."]
>>                        else tl
>
> //
>
> --
>  Marcus D. Gabriel, Ph.D.                         Saint Louis, FRANCE
>  http://www.marcus.gabriel.name            mailto:marcus at gabriel.name
>  Tel: +33.3.89.69.05.06                   Portable: +33.6.34.56.07.75
>
>
>