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

[Marcus D. Gabriel]

Hello Neil,

Thanks for the pointer Neil.  I will read the site.  Besides,
it allows me to submit a fixed version since I just found a bug!

Cheers,
- Marcus

P.S. 452 black box tests of my little command utility, and I
still forgot about a corner case.  Now there are 454 black box
test cases :).

Neil Mitchell wrote:
> 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