Re: [Haskell-cafe] File path programme

[robert dockins]

After the discussion about file paths over the last several days I went 
home and put together a quick trial implementation for unix file paths, 
with the idea of adding windows, SMB and maybe VMS (why not?) paths.  It 
is based on a Path class.  I'll post it later when I get home.  However, 
I will attempt to recreate the class definition from memory now to see 
if we can get some discussion going about the methods needed/desired, 
and whether or not this is a good approach.

data PathRoot
   = UnixFilesystemRoot
   | WindowsDrive Char
   | SMBShare String String
   | VMSDevice String
   | ... -- whatever else we need
class (Show p) => Path p where
   isAbsolute :: p -> Bool
   isRelative :: p -> Bool
   isRelative = not . isAbsolute
   basename :: p -> String
   parent :: p -> p
   pathAppend :: p -> p -> p  -- 2nd arg must be a relative path
   pathSeparator :: p -> Char
   pathParser :: Parser p     -- parsec parser
   parsePath :: String -> p
   parsePath str = case parse pathParser "" str of
                       Left e = error (Show e)
                       Right p = p
Other operations I think might be worthwhile:
pathRoot :: p -> Maybe PathRoot -- relative paths return Nothing
pathCleanup :: p -> p           -- remove .. and suchlike
commonAncestors :: p -> p -> p
pathFrom :: p -> p -> p       -- returns a relative path from the 1st to 
the 2nd
pathCompare :: p -> p -> ???  -- not sure what this should mean or return
hasExtension :: p -> String -> Bool
pathToForeign :: p -> IO (Ptr CChar)
pathFromForeign :: Ptr CChar -> IO p

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