[Haskell-cafe] Re: Suggested additions to
ndmitchell at gmail.com
Fri Sep 18 14:29:44 EDT 2009
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.
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
>> 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: +18.104.22.168.05.06 Portable: +22.214.171.124.07.75
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