[Haskell-cafe] Re: Suggested additions to
Marcus D. Gabriel
marcus at gabriel.name
Fri Sep 18 17:43:46 EDT 2009
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!
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.
> 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: +220.127.116.11.05.06 Portable: +18.104.22.168.07.75
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