[Haskell-cafe] Suggested additions to System.FilePath.Posix/Windows
Marcus D. Gabriel
marcus at gabriel.name
Thu Sep 17 05:58:32 EDT 2009
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,
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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