-- Hoogle documentation, generated by Haddock -- See Hoogle, http://www.haskell.org/hoogle/ -- | Library for manipulating FilePaths in a cross platform way. -- -- This package provides functionality for manipulating FilePath -- values, and is shipped with both GHC and the Haskell -- Platform. It provides three modules: -- -- -- -- All three modules provide the same API, and the same documentation -- (calling out differences in the different variants). @package filepath @version 1.4.2.1 -- | A library for FilePath manipulations, using Posix style paths -- on all platforms. Importing System.FilePath is usually better. -- -- Given the example FilePath: /directory/file.ext -- -- We can use the following functions to extract pieces. -- -- -- -- And we could have built an equivalent path with the following -- expressions: -- -- -- -- Each function in this module is documented with several examples, -- which are also used as tests. -- -- Here are a few examples of using the filepath functions -- together: -- -- Example 1: Find the possible locations of a Haskell module -- Test imported from module Main: -- -- 
--   [replaceFileName path_to_main "Test" <.> ext | ext <- ["hs","lhs"] ]
--
-- -- Example 2: Download a file from url and save it to -- disk: -- -- 
--   do let file = makeValid url
--      System.Directory.createDirectoryIfMissing True (takeDirectory file)
--
-- -- Example 3: Compile a Haskell file, putting the .hi -- file under interface: -- -- 
--   takeDirectory file </> "interface" </> (takeFileName file -<.> "hi")
--
-- -- References: [1] Naming Files, Paths and Namespaces (Microsoft -- MSDN) module System.FilePath.Posix -- | File and directory names are values of type String, whose -- precise meaning is operating system dependent. Files can be opened, -- yielding a handle which can then be used to operate on the contents of -- that file. type FilePath = String -- | The character that separates directories. In the case where more than -- one character is possible, pathSeparator is the 'ideal' one. -- -- 
--   Windows: pathSeparator == '\\'
--   Posix:   pathSeparator ==  '/'
--   isPathSeparator pathSeparator
--
pathSeparator :: Char -- | The list of all possible separators. -- -- 
--   Windows: pathSeparators == ['\\', '/']
--   Posix:   pathSeparators == ['/']
--   pathSeparator `elem` pathSeparators
--
pathSeparators :: [Char] -- | Rather than using (== pathSeparator), use this. Test -- if something is a path separator. -- -- 
--   isPathSeparator a == (a `elem` pathSeparators)
--
isPathSeparator :: Char -> Bool -- | The character that is used to separate the entries in the $PATH -- environment variable. -- -- 
--   Windows: searchPathSeparator == ';'
--   Posix:   searchPathSeparator == ':'
--
searchPathSeparator :: Char -- | Is the character a file separator? -- -- 
--   isSearchPathSeparator a == (a == searchPathSeparator)
--
isSearchPathSeparator :: Char -> Bool -- | File extension character -- -- 
--   extSeparator == '.'
--
extSeparator :: Char -- | Is the character an extension character? -- -- 
--   isExtSeparator a == (a == extSeparator)
--
isExtSeparator :: Char -> Bool -- | Take a string, split it on the searchPathSeparator character. -- Blank items are ignored on Windows, and converted to . on -- Posix. On Windows path elements are stripped of quotes. -- -- Follows the recommendations in -- http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap08.html -- -- 
--   Posix:   splitSearchPath "File1:File2:File3"  == ["File1","File2","File3"]
--   Posix:   splitSearchPath "File1::File2:File3" == ["File1",".","File2","File3"]
--   Windows: splitSearchPath "File1;File2;File3"  == ["File1","File2","File3"]
--   Windows: splitSearchPath "File1;;File2;File3" == ["File1","File2","File3"]
--   Windows: splitSearchPath "File1;\"File2\";File3" == ["File1","File2","File3"]
--
splitSearchPath :: String -> [FilePath] -- | Get a list of FilePaths in the $PATH variable. getSearchPath :: IO [FilePath] -- | Split on the extension. addExtension is the inverse. -- -- 
--   splitExtension "/directory/path.ext" == ("/directory/path",".ext")
--   uncurry (++) (splitExtension x) == x
--   Valid x => uncurry addExtension (splitExtension x) == x
--   splitExtension "file.txt" == ("file",".txt")
--   splitExtension "file" == ("file","")
--   splitExtension "file/file.txt" == ("file/file",".txt")
--   splitExtension "file.txt/boris" == ("file.txt/boris","")
--   splitExtension "file.txt/boris.ext" == ("file.txt/boris",".ext")
--   splitExtension "file/path.txt.bob.fred" == ("file/path.txt.bob",".fred")
--   splitExtension "file/path.txt/" == ("file/path.txt/","")
--
splitExtension :: FilePath -> (String, String) -- | Get the extension of a file, returns "" for no extension, -- .ext otherwise. -- -- 
--   takeExtension "/directory/path.ext" == ".ext"
--   takeExtension x == snd (splitExtension x)
--   Valid x => takeExtension (addExtension x "ext") == ".ext"
--   Valid x => takeExtension (replaceExtension x "ext") == ".ext"
--
takeExtension :: FilePath -> String -- | Set the extension of a file, overwriting one if already present, -- equivalent to -<.>. -- -- 
--   replaceExtension "/directory/path.txt" "ext" == "/directory/path.ext"
--   replaceExtension "/directory/path.txt" ".ext" == "/directory/path.ext"
--   replaceExtension "file.txt" ".bob" == "file.bob"
--   replaceExtension "file.txt" "bob" == "file.bob"
--   replaceExtension "file" ".bob" == "file.bob"
--   replaceExtension "file.txt" "" == "file"
--   replaceExtension "file.fred.bob" "txt" == "file.fred.txt"
--   replaceExtension x y == addExtension (dropExtension x) y
--
replaceExtension :: FilePath -> String -> FilePath -- | Remove the current extension and add another, equivalent to -- replaceExtension. -- -- 
--   "/directory/path.txt" -<.> "ext" == "/directory/path.ext"
--   "/directory/path.txt" -<.> ".ext" == "/directory/path.ext"
--   "foo.o" -<.> "c" == "foo.c"
--
(-<.>) :: FilePath -> String -> FilePath infixr 7 -<.> -- | Remove last extension, and the "." preceding it. -- -- 
--   dropExtension "/directory/path.ext" == "/directory/path"
--   dropExtension x == fst (splitExtension x)
--
dropExtension :: FilePath -> FilePath -- | Add an extension, even if there is already one there, equivalent to -- <.>. -- -- 
--   addExtension "/directory/path" "ext" == "/directory/path.ext"
--   addExtension "file.txt" "bib" == "file.txt.bib"
--   addExtension "file." ".bib" == "file..bib"
--   addExtension "file" ".bib" == "file.bib"
--   addExtension "/" "x" == "/.x"
--   addExtension x "" == x
--   Valid x => takeFileName (addExtension (addTrailingPathSeparator x) "ext") == ".ext"
--   Windows: addExtension "\\\\share" ".txt" == "\\\\share\\.txt"
--
addExtension :: FilePath -> String -> FilePath -- | Does the given filename have an extension? -- -- 
--   hasExtension "/directory/path.ext" == True
--   hasExtension "/directory/path" == False
--   null (takeExtension x) == not (hasExtension x)
--
hasExtension :: FilePath -> Bool -- | Add an extension, even if there is already one there, equivalent to -- addExtension. -- -- 
--   "/directory/path" <.> "ext" == "/directory/path.ext"
--   "/directory/path" <.> ".ext" == "/directory/path.ext"
--
(<.>) :: FilePath -> String -> FilePath infixr 7 <.> -- | Split on all extensions. -- -- 
--   splitExtensions "/directory/path.ext" == ("/directory/path",".ext")
--   splitExtensions "file.tar.gz" == ("file",".tar.gz")
--   uncurry (++) (splitExtensions x) == x
--   Valid x => uncurry addExtension (splitExtensions x) == x
--   splitExtensions "file.tar.gz" == ("file",".tar.gz")
--
splitExtensions :: FilePath -> (FilePath, String) -- | Drop all extensions. -- -- 
--   dropExtensions "/directory/path.ext" == "/directory/path"
--   dropExtensions "file.tar.gz" == "file"
--   not $ hasExtension $ dropExtensions x
--   not $ any isExtSeparator $ takeFileName $ dropExtensions x
--
dropExtensions :: FilePath -> FilePath -- | Get all extensions. -- -- 
--   takeExtensions "/directory/path.ext" == ".ext"
--   takeExtensions "file.tar.gz" == ".tar.gz"
--
takeExtensions :: FilePath -> String -- | Replace all extensions of a file with a new extension. Note that -- replaceExtension and addExtension both work for adding -- multiple extensions, so only required when you need to drop all -- extensions first. -- -- 
--   replaceExtensions "file.fred.bob" "txt" == "file.txt"
--   replaceExtensions "file.fred.bob" "tar.gz" == "file.tar.gz"
--
replaceExtensions :: FilePath -> String -> FilePath -- | Does the given filename have the specified extension? -- -- 
--   "png" `isExtensionOf` "/directory/file.png" == True
--   ".png" `isExtensionOf` "/directory/file.png" == True
--   ".tar.gz" `isExtensionOf` "bar/foo.tar.gz" == True
--   "ar.gz" `isExtensionOf` "bar/foo.tar.gz" == False
--   "png" `isExtensionOf` "/directory/file.png.jpg" == False
--   "csv/table.csv" `isExtensionOf` "/data/csv/table.csv" == False
--
isExtensionOf :: String -> FilePath -> Bool -- | Drop the given extension from a FilePath, and the "." -- preceding it. Returns Nothing if the FilePath does not have the -- given extension, or Just and the part before the extension if -- it does. -- -- This function can be more predictable than dropExtensions, -- especially if the filename might itself contain . characters. -- -- 
--   stripExtension "hs.o" "foo.x.hs.o" == Just "foo.x"
--   stripExtension "hi.o" "foo.x.hs.o" == Nothing
--   dropExtension x == fromJust (stripExtension (takeExtension x) x)
--   dropExtensions x == fromJust (stripExtension (takeExtensions x) x)
--   stripExtension ".c.d" "a.b.c.d"  == Just "a.b"
--   stripExtension ".c.d" "a.b..c.d" == Just "a.b."
--   stripExtension "baz"  "foo.bar"  == Nothing
--   stripExtension "bar"  "foobar"   == Nothing
--   stripExtension ""     x          == Just x
--
stripExtension :: String -> FilePath -> Maybe FilePath -- | Split a filename into directory and file. </> is the -- inverse. The first component will often end with a trailing slash. -- -- 
--   splitFileName "/directory/file.ext" == ("/directory/","file.ext")
--   Valid x => uncurry (</>) (splitFileName x) == x || fst (splitFileName x) == "./"
--   Valid x => isValid (fst (splitFileName x))
--   splitFileName "file/bob.txt" == ("file/", "bob.txt")
--   splitFileName "file/" == ("file/", "")
--   splitFileName "bob" == ("./", "bob")
--   Posix:   splitFileName "/" == ("/","")
--   Windows: splitFileName "c:" == ("c:","")
--
splitFileName :: FilePath -> (String, String) -- | Get the file name. -- -- 
--   takeFileName "/directory/file.ext" == "file.ext"
--   takeFileName "test/" == ""
--   takeFileName x `isSuffixOf` x
--   takeFileName x == snd (splitFileName x)
--   Valid x => takeFileName (replaceFileName x "fred") == "fred"
--   Valid x => takeFileName (x </> "fred") == "fred"
--   Valid x => isRelative (takeFileName x)
--
takeFileName :: FilePath -> FilePath -- | Set the filename. -- -- 
--   replaceFileName "/directory/other.txt" "file.ext" == "/directory/file.ext"
--   Valid x => replaceFileName x (takeFileName x) == x
--
replaceFileName :: FilePath -> String -> FilePath -- | Drop the filename. Unlike takeDirectory, this function will -- leave a trailing path separator on the directory. -- -- 
--   dropFileName "/directory/file.ext" == "/directory/"
--   dropFileName x == fst (splitFileName x)
--
dropFileName :: FilePath -> FilePath -- | Get the base name, without an extension or path. -- -- 
--   takeBaseName "/directory/file.ext" == "file"
--   takeBaseName "file/test.txt" == "test"
--   takeBaseName "dave.ext" == "dave"
--   takeBaseName "" == ""
--   takeBaseName "test" == "test"
--   takeBaseName (addTrailingPathSeparator x) == ""
--   takeBaseName "file/file.tar.gz" == "file.tar"
--
takeBaseName :: FilePath -> String -- | Set the base name. -- -- 
--   replaceBaseName "/directory/other.ext" "file" == "/directory/file.ext"
--   replaceBaseName "file/test.txt" "bob" == "file/bob.txt"
--   replaceBaseName "fred" "bill" == "bill"
--   replaceBaseName "/dave/fred/bob.gz.tar" "new" == "/dave/fred/new.tar"
--   Valid x => replaceBaseName x (takeBaseName x) == x
--
replaceBaseName :: FilePath -> String -> FilePath -- | Get the directory name, move up one level. -- -- 
--             takeDirectory "/directory/other.ext" == "/directory"
--             takeDirectory x `isPrefixOf` x || takeDirectory x == "."
--             takeDirectory "foo" == "."
--             takeDirectory "/" == "/"
--             takeDirectory "/foo" == "/"
--             takeDirectory "/foo/bar/baz" == "/foo/bar"
--             takeDirectory "/foo/bar/baz/" == "/foo/bar/baz"
--             takeDirectory "foo/bar/baz" == "foo/bar"
--   Windows:  takeDirectory "foo\\bar" == "foo"
--   Windows:  takeDirectory "foo\\bar\\\\" == "foo\\bar"
--   Windows:  takeDirectory "C:\\" == "C:\\"
--
takeDirectory :: FilePath -> FilePath -- | Set the directory, keeping the filename the same. -- -- 
--   replaceDirectory "root/file.ext" "/directory/" == "/directory/file.ext"
--   Valid x => replaceDirectory x (takeDirectory x) `equalFilePath` x
--
replaceDirectory :: FilePath -> String -> FilePath -- | An alias for </>. combine :: FilePath -> FilePath -> FilePath -- | Combine two paths with a path separator. If the second path starts -- with a path separator or a drive letter, then it returns the second. -- The intention is that readFile (dir </> file) -- will access the same file as setCurrentDirectory dir; readFile -- file. -- -- 
--   Posix:   "/directory" </> "file.ext" == "/directory/file.ext"
--   Windows: "/directory" </> "file.ext" == "/directory\\file.ext"
--            "directory" </> "/file.ext" == "/file.ext"
--   Valid x => (takeDirectory x </> takeFileName x) `equalFilePath` x
--
-- -- Combined: -- -- 
--   Posix:   "/" </> "test" == "/test"
--   Posix:   "home" </> "bob" == "home/bob"
--   Posix:   "x:" </> "foo" == "x:/foo"
--   Windows: "C:\\foo" </> "bar" == "C:\\foo\\bar"
--   Windows: "home" </> "bob" == "home\\bob"
--
-- -- Not combined: -- -- 
--   Posix:   "home" </> "/bob" == "/bob"
--   Windows: "home" </> "C:\\bob" == "C:\\bob"
--
-- -- Not combined (tricky): -- -- On Windows, if a filepath starts with a single slash, it is relative -- to the root of the current drive. In [1], this is (confusingly) -- referred to as an absolute path. The current behavior of -- </> is to never combine these forms. -- -- 
--   Windows: "home" </> "/bob" == "/bob"
--   Windows: "home" </> "\\bob" == "\\bob"
--   Windows: "C:\\home" </> "\\bob" == "\\bob"
--
-- -- On Windows, from [1]: "If a file name begins with only a disk -- designator but not the backslash after the colon, it is interpreted as -- a relative path to the current directory on the drive with the -- specified letter." The current behavior of </> is to -- never combine these forms. -- -- 
--   Windows: "D:\\foo" </> "C:bar" == "C:bar"
--   Windows: "C:\\foo" </> "C:bar" == "C:bar"
--
() :: FilePath -> FilePath -> FilePath infixr 5 -- | Split a path by the directory separator. -- -- 
--   splitPath "/directory/file.ext" == ["/","directory/","file.ext"]
--   concat (splitPath x) == x
--   splitPath "test//item/" == ["test//","item/"]
--   splitPath "test/item/file" == ["test/","item/","file"]
--   splitPath "" == []
--   Windows: splitPath "c:\\test\\path" == ["c:\\","test\\","path"]
--   Posix:   splitPath "/file/test" == ["/","file/","test"]
--
splitPath :: FilePath -> [FilePath] -- | Join path elements back together. -- -- 
--   joinPath ["/","directory/","file.ext"] == "/directory/file.ext"
--   Valid x => joinPath (splitPath x) == x
--   joinPath [] == ""
--   Posix: joinPath ["test","file","path"] == "test/file/path"
--
joinPath :: [FilePath] -> FilePath -- | Just as splitPath, but don't add the trailing slashes to each -- element. -- -- 
--            splitDirectories "/directory/file.ext" == ["/","directory","file.ext"]
--            splitDirectories "test/file" == ["test","file"]
--            splitDirectories "/test/file" == ["/","test","file"]
--   Windows: splitDirectories "C:\\test\\file" == ["C:\\", "test", "file"]
--            Valid x => joinPath (splitDirectories x) `equalFilePath` x
--            splitDirectories "" == []
--   Windows: splitDirectories "C:\\test\\\\\\file" == ["C:\\", "test", "file"]
--            splitDirectories "/test///file" == ["/","test","file"]
--
splitDirectories :: FilePath -> [FilePath] -- | Split a path into a drive and a path. On Posix, / is a Drive. -- -- 
--   uncurry (++) (splitDrive x) == x
--   Windows: splitDrive "file" == ("","file")
--   Windows: splitDrive "c:/file" == ("c:/","file")
--   Windows: splitDrive "c:\\file" == ("c:\\","file")
--   Windows: splitDrive "\\\\shared\\test" == ("\\\\shared\\","test")
--   Windows: splitDrive "\\\\shared" == ("\\\\shared","")
--   Windows: splitDrive "\\\\?\\UNC\\shared\\file" == ("\\\\?\\UNC\\shared\\","file")
--   Windows: splitDrive "\\\\?\\UNCshared\\file" == ("\\\\?\\","UNCshared\\file")
--   Windows: splitDrive "\\\\?\\d:\\file" == ("\\\\?\\d:\\","file")
--   Windows: splitDrive "/d" == ("","/d")
--   Posix:   splitDrive "/test" == ("/","test")
--   Posix:   splitDrive "//test" == ("//","test")
--   Posix:   splitDrive "test/file" == ("","test/file")
--   Posix:   splitDrive "file" == ("","file")
--
splitDrive :: FilePath -> (FilePath, FilePath) -- | Join a drive and the rest of the path. -- -- 
--   Valid x => uncurry joinDrive (splitDrive x) == x
--   Windows: joinDrive "C:" "foo" == "C:foo"
--   Windows: joinDrive "C:\\" "bar" == "C:\\bar"
--   Windows: joinDrive "\\\\share" "foo" == "\\\\share\\foo"
--   Windows: joinDrive "/:" "foo" == "/:\\foo"
--
joinDrive :: FilePath -> FilePath -> FilePath -- | Get the drive from a filepath. -- -- 
--   takeDrive x == fst (splitDrive x)
--
takeDrive :: FilePath -> FilePath -- | Does a path have a drive. -- -- 
--   not (hasDrive x) == null (takeDrive x)
--   Posix:   hasDrive "/foo" == True
--   Windows: hasDrive "C:\\foo" == True
--   Windows: hasDrive "C:foo" == True
--            hasDrive "foo" == False
--            hasDrive "" == False
--
hasDrive :: FilePath -> Bool -- | Delete the drive, if it exists. -- -- 
--   dropDrive x == snd (splitDrive x)
--
dropDrive :: FilePath -> FilePath -- | Is an element a drive -- -- 
--   Posix:   isDrive "/" == True
--   Posix:   isDrive "/foo" == False
--   Windows: isDrive "C:\\" == True
--   Windows: isDrive "C:\\foo" == False
--            isDrive "" == False
--
isDrive :: FilePath -> Bool -- | Is an item either a directory or the last character a path separator? -- -- 
--   hasTrailingPathSeparator "test" == False
--   hasTrailingPathSeparator "test/" == True
--
hasTrailingPathSeparator :: FilePath -> Bool -- | Add a trailing file path separator if one is not already present. -- -- 
--   hasTrailingPathSeparator (addTrailingPathSeparator x)
--   hasTrailingPathSeparator x ==> addTrailingPathSeparator x == x
--   Posix:    addTrailingPathSeparator "test/rest" == "test/rest/"
--
addTrailingPathSeparator :: FilePath -> FilePath -- | Remove any trailing path separators -- -- 
--   dropTrailingPathSeparator "file/test/" == "file/test"
--             dropTrailingPathSeparator "/" == "/"
--   Windows:  dropTrailingPathSeparator "\\" == "\\"
--   Posix:    not (hasTrailingPathSeparator (dropTrailingPathSeparator x)) || isDrive x
--
dropTrailingPathSeparator :: FilePath -> FilePath -- | Normalise a file -- -- -- -- 
--   Posix:   normalise "/file/\\test////" == "/file/\\test/"
--   Posix:   normalise "/file/./test" == "/file/test"
--   Posix:   normalise "/test/file/../bob/fred/" == "/test/file/../bob/fred/"
--   Posix:   normalise "../bob/fred/" == "../bob/fred/"
--   Posix:   normalise "./bob/fred/" == "bob/fred/"
--   Windows: normalise "c:\\file/bob\\" == "C:\\file\\bob\\"
--   Windows: normalise "c:\\" == "C:\\"
--   Windows: normalise "C:.\\" == "C:"
--   Windows: normalise "\\\\server\\test" == "\\\\server\\test"
--   Windows: normalise "//server/test" == "\\\\server\\test"
--   Windows: normalise "c:/file" == "C:\\file"
--   Windows: normalise "/file" == "\\file"
--   Windows: normalise "\\" == "\\"
--   Windows: normalise "/./" == "\\"
--            normalise "." == "."
--   Posix:   normalise "./" == "./"
--   Posix:   normalise "./." == "./"
--   Posix:   normalise "/./" == "/"
--   Posix:   normalise "/" == "/"
--   Posix:   normalise "bob/fred/." == "bob/fred/"
--   Posix:   normalise "//home" == "/home"
--
normalise :: FilePath -> FilePath -- | Equality of two FilePaths. If you call -- System.Directory.canonicalizePath first this has a much -- better chance of working. Note that this doesn't follow symlinks or -- DOSNAM~1s. -- -- 
--            x == y ==> equalFilePath x y
--            normalise x == normalise y ==> equalFilePath x y
--            equalFilePath "foo" "foo/"
--            not (equalFilePath "foo" "/foo")
--   Posix:   not (equalFilePath "foo" "FOO")
--   Windows: equalFilePath "foo" "FOO"
--   Windows: not (equalFilePath "C:" "C:/")
--
equalFilePath :: FilePath -> FilePath -> Bool -- | Contract a filename, based on a relative path. Note that the resulting -- path will never introduce .. paths, as the presence of -- symlinks means ../b may not reach a/b if it starts -- from a/c. For a worked example see this blog post. -- -- The corresponding makeAbsolute function can be found in -- System.Directory. -- -- 
--            makeRelative "/directory" "/directory/file.ext" == "file.ext"
--            Valid x => makeRelative (takeDirectory x) x `equalFilePath` takeFileName x
--            makeRelative x x == "."
--            Valid x y => equalFilePath x y || (isRelative x && makeRelative y x == x) || equalFilePath (y </> makeRelative y x) x
--   Windows: makeRelative "C:\\Home" "c:\\home\\bob" == "bob"
--   Windows: makeRelative "C:\\Home" "c:/home/bob" == "bob"
--   Windows: makeRelative "C:\\Home" "D:\\Home\\Bob" == "D:\\Home\\Bob"
--   Windows: makeRelative "C:\\Home" "C:Home\\Bob" == "C:Home\\Bob"
--   Windows: makeRelative "/Home" "/home/bob" == "bob"
--   Windows: makeRelative "/" "//" == "//"
--   Posix:   makeRelative "/Home" "/home/bob" == "/home/bob"
--   Posix:   makeRelative "/home/" "/home/bob/foo/bar" == "bob/foo/bar"
--   Posix:   makeRelative "/fred" "bob" == "bob"
--   Posix:   makeRelative "/file/test" "/file/test/fred" == "fred"
--   Posix:   makeRelative "/file/test" "/file/test/fred/" == "fred/"
--   Posix:   makeRelative "some/path" "some/path/a/b/c" == "a/b/c"
--
makeRelative :: FilePath -> FilePath -> FilePath -- | Is a path relative, or is it fixed to the root? -- -- 
--   Windows: isRelative "path\\test" == True
--   Windows: isRelative "c:\\test" == False
--   Windows: isRelative "c:test" == True
--   Windows: isRelative "c:\\" == False
--   Windows: isRelative "c:/" == False
--   Windows: isRelative "c:" == True
--   Windows: isRelative "\\\\foo" == False
--   Windows: isRelative "\\\\?\\foo" == False
--   Windows: isRelative "\\\\?\\UNC\\foo" == False
--   Windows: isRelative "/foo" == True
--   Windows: isRelative "\\foo" == True
--   Posix:   isRelative "test/path" == True
--   Posix:   isRelative "/test" == False
--   Posix:   isRelative "/" == False
--
-- -- According to [1]: -- -- isRelative :: FilePath -> Bool -- | 
--   not . isRelative
--
-- -- 
--   isAbsolute x == not (isRelative x)
--
isAbsolute :: FilePath -> Bool -- | Is a FilePath valid, i.e. could you create a file like it? This -- function checks for invalid names, and invalid characters, but does -- not check if length limits are exceeded, as these are typically -- filesystem dependent. -- -- 
--            isValid "" == False
--            isValid "\0" == False
--   Posix:   isValid "/random_ path:*" == True
--   Posix:   isValid x == not (null x)
--   Windows: isValid "c:\\test" == True
--   Windows: isValid "c:\\test:of_test" == False
--   Windows: isValid "test*" == False
--   Windows: isValid "c:\\test\\nul" == False
--   Windows: isValid "c:\\test\\prn.txt" == False
--   Windows: isValid "c:\\nul\\file" == False
--   Windows: isValid "\\\\" == False
--   Windows: isValid "\\\\\\foo" == False
--   Windows: isValid "\\\\?\\D:file" == False
--   Windows: isValid "foo\tbar" == False
--   Windows: isValid "nul .txt" == False
--   Windows: isValid " nul.txt" == True
--
isValid :: FilePath -> Bool -- | Take a FilePath and make it valid; does not change already valid -- FilePaths. -- -- 
--   isValid (makeValid x)
--   isValid x ==> makeValid x == x
--   makeValid "" == "_"
--   makeValid "file\0name" == "file_name"
--   Windows: makeValid "c:\\already\\/valid" == "c:\\already\\/valid"
--   Windows: makeValid "c:\\test:of_test" == "c:\\test_of_test"
--   Windows: makeValid "test*" == "test_"
--   Windows: makeValid "c:\\test\\nul" == "c:\\test\\nul_"
--   Windows: makeValid "c:\\test\\prn.txt" == "c:\\test\\prn_.txt"
--   Windows: makeValid "c:\\test/prn.txt" == "c:\\test/prn_.txt"
--   Windows: makeValid "c:\\nul\\file" == "c:\\nul_\\file"
--   Windows: makeValid "\\\\\\foo" == "\\\\drive"
--   Windows: makeValid "\\\\?\\D:file" == "\\\\?\\D:\\file"
--   Windows: makeValid "nul .txt" == "nul _.txt"
--
makeValid :: FilePath -> FilePath -- | A library for FilePath manipulations, using Posix or Windows -- filepaths depending on the platform. -- -- Both System.FilePath.Posix and System.FilePath.Windows -- provide the same interface. See either for examples and a list of the -- available functions. module System.FilePath -- | A library for FilePath manipulations, using Windows style paths -- on all platforms. Importing System.FilePath is usually better. -- -- Given the example FilePath: /directory/file.ext -- -- We can use the following functions to extract pieces. -- -- -- -- And we could have built an equivalent path with the following -- expressions: -- -- -- -- Each function in this module is documented with several examples, -- which are also used as tests. -- -- Here are a few examples of using the filepath functions -- together: -- -- Example 1: Find the possible locations of a Haskell module -- Test imported from module Main: -- -- 
--   [replaceFileName path_to_main "Test" <.> ext | ext <- ["hs","lhs"] ]
--
-- -- Example 2: Download a file from url and save it to -- disk: -- -- 
--   do let file = makeValid url
--      System.Directory.createDirectoryIfMissing True (takeDirectory file)
--
-- -- Example 3: Compile a Haskell file, putting the .hi -- file under interface: -- -- 
--   takeDirectory file </> "interface" </> (takeFileName file -<.> "hi")
--
-- -- References: [1] Naming Files, Paths and Namespaces (Microsoft -- MSDN) module System.FilePath.Windows -- | File and directory names are values of type String, whose -- precise meaning is operating system dependent. Files can be opened, -- yielding a handle which can then be used to operate on the contents of -- that file. type FilePath = String -- | The character that separates directories. In the case where more than -- one character is possible, pathSeparator is the 'ideal' one. -- -- 
--   Windows: pathSeparator == '\\'
--   Posix:   pathSeparator ==  '/'
--   isPathSeparator pathSeparator
--
pathSeparator :: Char -- | The list of all possible separators. -- -- 
--   Windows: pathSeparators == ['\\', '/']
--   Posix:   pathSeparators == ['/']
--   pathSeparator `elem` pathSeparators
--
pathSeparators :: [Char] -- | Rather than using (== pathSeparator), use this. Test -- if something is a path separator. -- -- 
--   isPathSeparator a == (a `elem` pathSeparators)
--
isPathSeparator :: Char -> Bool -- | The character that is used to separate the entries in the $PATH -- environment variable. -- -- 
--   Windows: searchPathSeparator == ';'
--   Posix:   searchPathSeparator == ':'
--
searchPathSeparator :: Char -- | Is the character a file separator? -- -- 
--   isSearchPathSeparator a == (a == searchPathSeparator)
--
isSearchPathSeparator :: Char -> Bool -- | File extension character -- -- 
--   extSeparator == '.'
--
extSeparator :: Char -- | Is the character an extension character? -- -- 
--   isExtSeparator a == (a == extSeparator)
--
isExtSeparator :: Char -> Bool -- | Take a string, split it on the searchPathSeparator character. -- Blank items are ignored on Windows, and converted to . on -- Posix. On Windows path elements are stripped of quotes. -- -- Follows the recommendations in -- http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap08.html -- -- 
--   Posix:   splitSearchPath "File1:File2:File3"  == ["File1","File2","File3"]
--   Posix:   splitSearchPath "File1::File2:File3" == ["File1",".","File2","File3"]
--   Windows: splitSearchPath "File1;File2;File3"  == ["File1","File2","File3"]
--   Windows: splitSearchPath "File1;;File2;File3" == ["File1","File2","File3"]
--   Windows: splitSearchPath "File1;\"File2\";File3" == ["File1","File2","File3"]
--
splitSearchPath :: String -> [FilePath] -- | Get a list of FilePaths in the $PATH variable. getSearchPath :: IO [FilePath] -- | Split on the extension. addExtension is the inverse. -- -- 
--   splitExtension "/directory/path.ext" == ("/directory/path",".ext")
--   uncurry (++) (splitExtension x) == x
--   Valid x => uncurry addExtension (splitExtension x) == x
--   splitExtension "file.txt" == ("file",".txt")
--   splitExtension "file" == ("file","")
--   splitExtension "file/file.txt" == ("file/file",".txt")
--   splitExtension "file.txt/boris" == ("file.txt/boris","")
--   splitExtension "file.txt/boris.ext" == ("file.txt/boris",".ext")
--   splitExtension "file/path.txt.bob.fred" == ("file/path.txt.bob",".fred")
--   splitExtension "file/path.txt/" == ("file/path.txt/","")
--
splitExtension :: FilePath -> (String, String) -- | Get the extension of a file, returns "" for no extension, -- .ext otherwise. -- -- 
--   takeExtension "/directory/path.ext" == ".ext"
--   takeExtension x == snd (splitExtension x)
--   Valid x => takeExtension (addExtension x "ext") == ".ext"
--   Valid x => takeExtension (replaceExtension x "ext") == ".ext"
--
takeExtension :: FilePath -> String -- | Set the extension of a file, overwriting one if already present, -- equivalent to -<.>. -- -- 
--   replaceExtension "/directory/path.txt" "ext" == "/directory/path.ext"
--   replaceExtension "/directory/path.txt" ".ext" == "/directory/path.ext"
--   replaceExtension "file.txt" ".bob" == "file.bob"
--   replaceExtension "file.txt" "bob" == "file.bob"
--   replaceExtension "file" ".bob" == "file.bob"
--   replaceExtension "file.txt" "" == "file"
--   replaceExtension "file.fred.bob" "txt" == "file.fred.txt"
--   replaceExtension x y == addExtension (dropExtension x) y
--
replaceExtension :: FilePath -> String -> FilePath -- | Remove the current extension and add another, equivalent to -- replaceExtension. -- -- 
--   "/directory/path.txt" -<.> "ext" == "/directory/path.ext"
--   "/directory/path.txt" -<.> ".ext" == "/directory/path.ext"
--   "foo.o" -<.> "c" == "foo.c"
--
(-<.>) :: FilePath -> String -> FilePath infixr 7 -<.> -- | Remove last extension, and the "." preceding it. -- -- 
--   dropExtension "/directory/path.ext" == "/directory/path"
--   dropExtension x == fst (splitExtension x)
--
dropExtension :: FilePath -> FilePath -- | Add an extension, even if there is already one there, equivalent to -- <.>. -- -- 
--   addExtension "/directory/path" "ext" == "/directory/path.ext"
--   addExtension "file.txt" "bib" == "file.txt.bib"
--   addExtension "file." ".bib" == "file..bib"
--   addExtension "file" ".bib" == "file.bib"
--   addExtension "/" "x" == "/.x"
--   addExtension x "" == x
--   Valid x => takeFileName (addExtension (addTrailingPathSeparator x) "ext") == ".ext"
--   Windows: addExtension "\\\\share" ".txt" == "\\\\share\\.txt"
--
addExtension :: FilePath -> String -> FilePath -- | Does the given filename have an extension? -- -- 
--   hasExtension "/directory/path.ext" == True
--   hasExtension "/directory/path" == False
--   null (takeExtension x) == not (hasExtension x)
--
hasExtension :: FilePath -> Bool -- | Add an extension, even if there is already one there, equivalent to -- addExtension. -- -- 
--   "/directory/path" <.> "ext" == "/directory/path.ext"
--   "/directory/path" <.> ".ext" == "/directory/path.ext"
--
(<.>) :: FilePath -> String -> FilePath infixr 7 <.> -- | Split on all extensions. -- -- 
--   splitExtensions "/directory/path.ext" == ("/directory/path",".ext")
--   splitExtensions "file.tar.gz" == ("file",".tar.gz")
--   uncurry (++) (splitExtensions x) == x
--   Valid x => uncurry addExtension (splitExtensions x) == x
--   splitExtensions "file.tar.gz" == ("file",".tar.gz")
--
splitExtensions :: FilePath -> (FilePath, String) -- | Drop all extensions. -- -- 
--   dropExtensions "/directory/path.ext" == "/directory/path"
--   dropExtensions "file.tar.gz" == "file"
--   not $ hasExtension $ dropExtensions x
--   not $ any isExtSeparator $ takeFileName $ dropExtensions x
--
dropExtensions :: FilePath -> FilePath -- | Get all extensions. -- -- 
--   takeExtensions "/directory/path.ext" == ".ext"
--   takeExtensions "file.tar.gz" == ".tar.gz"
--
takeExtensions :: FilePath -> String -- | Replace all extensions of a file with a new extension. Note that -- replaceExtension and addExtension both work for adding -- multiple extensions, so only required when you need to drop all -- extensions first. -- -- 
--   replaceExtensions "file.fred.bob" "txt" == "file.txt"
--   replaceExtensions "file.fred.bob" "tar.gz" == "file.tar.gz"
--
replaceExtensions :: FilePath -> String -> FilePath -- | Does the given filename have the specified extension? -- -- 
--   "png" `isExtensionOf` "/directory/file.png" == True
--   ".png" `isExtensionOf` "/directory/file.png" == True
--   ".tar.gz" `isExtensionOf` "bar/foo.tar.gz" == True
--   "ar.gz" `isExtensionOf` "bar/foo.tar.gz" == False
--   "png" `isExtensionOf` "/directory/file.png.jpg" == False
--   "csv/table.csv" `isExtensionOf` "/data/csv/table.csv" == False
--
isExtensionOf :: String -> FilePath -> Bool -- | Drop the given extension from a FilePath, and the "." -- preceding it. Returns Nothing if the FilePath does not have the -- given extension, or Just and the part before the extension if -- it does. -- -- This function can be more predictable than dropExtensions, -- especially if the filename might itself contain . characters. -- -- 
--   stripExtension "hs.o" "foo.x.hs.o" == Just "foo.x"
--   stripExtension "hi.o" "foo.x.hs.o" == Nothing
--   dropExtension x == fromJust (stripExtension (takeExtension x) x)
--   dropExtensions x == fromJust (stripExtension (takeExtensions x) x)
--   stripExtension ".c.d" "a.b.c.d"  == Just "a.b"
--   stripExtension ".c.d" "a.b..c.d" == Just "a.b."
--   stripExtension "baz"  "foo.bar"  == Nothing
--   stripExtension "bar"  "foobar"   == Nothing
--   stripExtension ""     x          == Just x
--
stripExtension :: String -> FilePath -> Maybe FilePath -- | Split a filename into directory and file. </> is the -- inverse. The first component will often end with a trailing slash. -- -- 
--   splitFileName "/directory/file.ext" == ("/directory/","file.ext")
--   Valid x => uncurry (</>) (splitFileName x) == x || fst (splitFileName x) == "./"
--   Valid x => isValid (fst (splitFileName x))
--   splitFileName "file/bob.txt" == ("file/", "bob.txt")
--   splitFileName "file/" == ("file/", "")
--   splitFileName "bob" == ("./", "bob")
--   Posix:   splitFileName "/" == ("/","")
--   Windows: splitFileName "c:" == ("c:","")
--
splitFileName :: FilePath -> (String, String) -- | Get the file name. -- -- 
--   takeFileName "/directory/file.ext" == "file.ext"
--   takeFileName "test/" == ""
--   takeFileName x `isSuffixOf` x
--   takeFileName x == snd (splitFileName x)
--   Valid x => takeFileName (replaceFileName x "fred") == "fred"
--   Valid x => takeFileName (x </> "fred") == "fred"
--   Valid x => isRelative (takeFileName x)
--
takeFileName :: FilePath -> FilePath -- | Set the filename. -- -- 
--   replaceFileName "/directory/other.txt" "file.ext" == "/directory/file.ext"
--   Valid x => replaceFileName x (takeFileName x) == x
--
replaceFileName :: FilePath -> String -> FilePath -- | Drop the filename. Unlike takeDirectory, this function will -- leave a trailing path separator on the directory. -- -- 
--   dropFileName "/directory/file.ext" == "/directory/"
--   dropFileName x == fst (splitFileName x)
--
dropFileName :: FilePath -> FilePath -- | Get the base name, without an extension or path. -- -- 
--   takeBaseName "/directory/file.ext" == "file"
--   takeBaseName "file/test.txt" == "test"
--   takeBaseName "dave.ext" == "dave"
--   takeBaseName "" == ""
--   takeBaseName "test" == "test"
--   takeBaseName (addTrailingPathSeparator x) == ""
--   takeBaseName "file/file.tar.gz" == "file.tar"
--
takeBaseName :: FilePath -> String -- | Set the base name. -- -- 
--   replaceBaseName "/directory/other.ext" "file" == "/directory/file.ext"
--   replaceBaseName "file/test.txt" "bob" == "file/bob.txt"
--   replaceBaseName "fred" "bill" == "bill"
--   replaceBaseName "/dave/fred/bob.gz.tar" "new" == "/dave/fred/new.tar"
--   Valid x => replaceBaseName x (takeBaseName x) == x
--
replaceBaseName :: FilePath -> String -> FilePath -- | Get the directory name, move up one level. -- -- 
--             takeDirectory "/directory/other.ext" == "/directory"
--             takeDirectory x `isPrefixOf` x || takeDirectory x == "."
--             takeDirectory "foo" == "."
--             takeDirectory "/" == "/"
--             takeDirectory "/foo" == "/"
--             takeDirectory "/foo/bar/baz" == "/foo/bar"
--             takeDirectory "/foo/bar/baz/" == "/foo/bar/baz"
--             takeDirectory "foo/bar/baz" == "foo/bar"
--   Windows:  takeDirectory "foo\\bar" == "foo"
--   Windows:  takeDirectory "foo\\bar\\\\" == "foo\\bar"
--   Windows:  takeDirectory "C:\\" == "C:\\"
--
takeDirectory :: FilePath -> FilePath -- | Set the directory, keeping the filename the same. -- -- 
--   replaceDirectory "root/file.ext" "/directory/" == "/directory/file.ext"
--   Valid x => replaceDirectory x (takeDirectory x) `equalFilePath` x
--
replaceDirectory :: FilePath -> String -> FilePath -- | An alias for </>. combine :: FilePath -> FilePath -> FilePath -- | Combine two paths with a path separator. If the second path starts -- with a path separator or a drive letter, then it returns the second. -- The intention is that readFile (dir </> file) -- will access the same file as setCurrentDirectory dir; readFile -- file. -- -- 
--   Posix:   "/directory" </> "file.ext" == "/directory/file.ext"
--   Windows: "/directory" </> "file.ext" == "/directory\\file.ext"
--            "directory" </> "/file.ext" == "/file.ext"
--   Valid x => (takeDirectory x </> takeFileName x) `equalFilePath` x
--
-- -- Combined: -- -- 
--   Posix:   "/" </> "test" == "/test"
--   Posix:   "home" </> "bob" == "home/bob"
--   Posix:   "x:" </> "foo" == "x:/foo"
--   Windows: "C:\\foo" </> "bar" == "C:\\foo\\bar"
--   Windows: "home" </> "bob" == "home\\bob"
--
-- -- Not combined: -- -- 
--   Posix:   "home" </> "/bob" == "/bob"
--   Windows: "home" </> "C:\\bob" == "C:\\bob"
--
-- -- Not combined (tricky): -- -- On Windows, if a filepath starts with a single slash, it is relative -- to the root of the current drive. In [1], this is (confusingly) -- referred to as an absolute path. The current behavior of -- </> is to never combine these forms. -- -- 
--   Windows: "home" </> "/bob" == "/bob"
--   Windows: "home" </> "\\bob" == "\\bob"
--   Windows: "C:\\home" </> "\\bob" == "\\bob"
--
-- -- On Windows, from [1]: "If a file name begins with only a disk -- designator but not the backslash after the colon, it is interpreted as -- a relative path to the current directory on the drive with the -- specified letter." The current behavior of </> is to -- never combine these forms. -- -- 
--   Windows: "D:\\foo" </> "C:bar" == "C:bar"
--   Windows: "C:\\foo" </> "C:bar" == "C:bar"
--
() :: FilePath -> FilePath -> FilePath infixr 5 -- | Split a path by the directory separator. -- -- 
--   splitPath "/directory/file.ext" == ["/","directory/","file.ext"]
--   concat (splitPath x) == x
--   splitPath "test//item/" == ["test//","item/"]
--   splitPath "test/item/file" == ["test/","item/","file"]
--   splitPath "" == []
--   Windows: splitPath "c:\\test\\path" == ["c:\\","test\\","path"]
--   Posix:   splitPath "/file/test" == ["/","file/","test"]
--
splitPath :: FilePath -> [FilePath] -- | Join path elements back together. -- -- 
--   joinPath ["/","directory/","file.ext"] == "/directory/file.ext"
--   Valid x => joinPath (splitPath x) == x
--   joinPath [] == ""
--   Posix: joinPath ["test","file","path"] == "test/file/path"
--
joinPath :: [FilePath] -> FilePath -- | Just as splitPath, but don't add the trailing slashes to each -- element. -- -- 
--            splitDirectories "/directory/file.ext" == ["/","directory","file.ext"]
--            splitDirectories "test/file" == ["test","file"]
--            splitDirectories "/test/file" == ["/","test","file"]
--   Windows: splitDirectories "C:\\test\\file" == ["C:\\", "test", "file"]
--            Valid x => joinPath (splitDirectories x) `equalFilePath` x
--            splitDirectories "" == []
--   Windows: splitDirectories "C:\\test\\\\\\file" == ["C:\\", "test", "file"]
--            splitDirectories "/test///file" == ["/","test","file"]
--
splitDirectories :: FilePath -> [FilePath] -- | Split a path into a drive and a path. On Posix, / is a Drive. -- -- 
--   uncurry (++) (splitDrive x) == x
--   Windows: splitDrive "file" == ("","file")
--   Windows: splitDrive "c:/file" == ("c:/","file")
--   Windows: splitDrive "c:\\file" == ("c:\\","file")
--   Windows: splitDrive "\\\\shared\\test" == ("\\\\shared\\","test")
--   Windows: splitDrive "\\\\shared" == ("\\\\shared","")
--   Windows: splitDrive "\\\\?\\UNC\\shared\\file" == ("\\\\?\\UNC\\shared\\","file")
--   Windows: splitDrive "\\\\?\\UNCshared\\file" == ("\\\\?\\","UNCshared\\file")
--   Windows: splitDrive "\\\\?\\d:\\file" == ("\\\\?\\d:\\","file")
--   Windows: splitDrive "/d" == ("","/d")
--   Posix:   splitDrive "/test" == ("/","test")
--   Posix:   splitDrive "//test" == ("//","test")
--   Posix:   splitDrive "test/file" == ("","test/file")
--   Posix:   splitDrive "file" == ("","file")
--
splitDrive :: FilePath -> (FilePath, FilePath) -- | Join a drive and the rest of the path. -- -- 
--   Valid x => uncurry joinDrive (splitDrive x) == x
--   Windows: joinDrive "C:" "foo" == "C:foo"
--   Windows: joinDrive "C:\\" "bar" == "C:\\bar"
--   Windows: joinDrive "\\\\share" "foo" == "\\\\share\\foo"
--   Windows: joinDrive "/:" "foo" == "/:\\foo"
--
joinDrive :: FilePath -> FilePath -> FilePath -- | Get the drive from a filepath. -- -- 
--   takeDrive x == fst (splitDrive x)
--
takeDrive :: FilePath -> FilePath -- | Does a path have a drive. -- -- 
--   not (hasDrive x) == null (takeDrive x)
--   Posix:   hasDrive "/foo" == True
--   Windows: hasDrive "C:\\foo" == True
--   Windows: hasDrive "C:foo" == True
--            hasDrive "foo" == False
--            hasDrive "" == False
--
hasDrive :: FilePath -> Bool -- | Delete the drive, if it exists. -- -- 
--   dropDrive x == snd (splitDrive x)
--
dropDrive :: FilePath -> FilePath -- | Is an element a drive -- -- 
--   Posix:   isDrive "/" == True
--   Posix:   isDrive "/foo" == False
--   Windows: isDrive "C:\\" == True
--   Windows: isDrive "C:\\foo" == False
--            isDrive "" == False
--
isDrive :: FilePath -> Bool -- | Is an item either a directory or the last character a path separator? -- -- 
--   hasTrailingPathSeparator "test" == False
--   hasTrailingPathSeparator "test/" == True
--
hasTrailingPathSeparator :: FilePath -> Bool -- | Add a trailing file path separator if one is not already present. -- -- 
--   hasTrailingPathSeparator (addTrailingPathSeparator x)
--   hasTrailingPathSeparator x ==> addTrailingPathSeparator x == x
--   Posix:    addTrailingPathSeparator "test/rest" == "test/rest/"
--
addTrailingPathSeparator :: FilePath -> FilePath -- | Remove any trailing path separators -- -- 
--   dropTrailingPathSeparator "file/test/" == "file/test"
--             dropTrailingPathSeparator "/" == "/"
--   Windows:  dropTrailingPathSeparator "\\" == "\\"
--   Posix:    not (hasTrailingPathSeparator (dropTrailingPathSeparator x)) || isDrive x
--
dropTrailingPathSeparator :: FilePath -> FilePath -- | Normalise a file -- -- -- -- 
--   Posix:   normalise "/file/\\test////" == "/file/\\test/"
--   Posix:   normalise "/file/./test" == "/file/test"
--   Posix:   normalise "/test/file/../bob/fred/" == "/test/file/../bob/fred/"
--   Posix:   normalise "../bob/fred/" == "../bob/fred/"
--   Posix:   normalise "./bob/fred/" == "bob/fred/"
--   Windows: normalise "c:\\file/bob\\" == "C:\\file\\bob\\"
--   Windows: normalise "c:\\" == "C:\\"
--   Windows: normalise "C:.\\" == "C:"
--   Windows: normalise "\\\\server\\test" == "\\\\server\\test"
--   Windows: normalise "//server/test" == "\\\\server\\test"
--   Windows: normalise "c:/file" == "C:\\file"
--   Windows: normalise "/file" == "\\file"
--   Windows: normalise "\\" == "\\"
--   Windows: normalise "/./" == "\\"
--            normalise "." == "."
--   Posix:   normalise "./" == "./"
--   Posix:   normalise "./." == "./"
--   Posix:   normalise "/./" == "/"
--   Posix:   normalise "/" == "/"
--   Posix:   normalise "bob/fred/." == "bob/fred/"
--   Posix:   normalise "//home" == "/home"
--
normalise :: FilePath -> FilePath -- | Equality of two FilePaths. If you call -- System.Directory.canonicalizePath first this has a much -- better chance of working. Note that this doesn't follow symlinks or -- DOSNAM~1s. -- -- 
--            x == y ==> equalFilePath x y
--            normalise x == normalise y ==> equalFilePath x y
--            equalFilePath "foo" "foo/"
--            not (equalFilePath "foo" "/foo")
--   Posix:   not (equalFilePath "foo" "FOO")
--   Windows: equalFilePath "foo" "FOO"
--   Windows: not (equalFilePath "C:" "C:/")
--
equalFilePath :: FilePath -> FilePath -> Bool -- | Contract a filename, based on a relative path. Note that the resulting -- path will never introduce .. paths, as the presence of -- symlinks means ../b may not reach a/b if it starts -- from a/c. For a worked example see this blog post. -- -- The corresponding makeAbsolute function can be found in -- System.Directory. -- -- 
--            makeRelative "/directory" "/directory/file.ext" == "file.ext"
--            Valid x => makeRelative (takeDirectory x) x `equalFilePath` takeFileName x
--            makeRelative x x == "."
--            Valid x y => equalFilePath x y || (isRelative x && makeRelative y x == x) || equalFilePath (y </> makeRelative y x) x
--   Windows: makeRelative "C:\\Home" "c:\\home\\bob" == "bob"
--   Windows: makeRelative "C:\\Home" "c:/home/bob" == "bob"
--   Windows: makeRelative "C:\\Home" "D:\\Home\\Bob" == "D:\\Home\\Bob"
--   Windows: makeRelative "C:\\Home" "C:Home\\Bob" == "C:Home\\Bob"
--   Windows: makeRelative "/Home" "/home/bob" == "bob"
--   Windows: makeRelative "/" "//" == "//"
--   Posix:   makeRelative "/Home" "/home/bob" == "/home/bob"
--   Posix:   makeRelative "/home/" "/home/bob/foo/bar" == "bob/foo/bar"
--   Posix:   makeRelative "/fred" "bob" == "bob"
--   Posix:   makeRelative "/file/test" "/file/test/fred" == "fred"
--   Posix:   makeRelative "/file/test" "/file/test/fred/" == "fred/"
--   Posix:   makeRelative "some/path" "some/path/a/b/c" == "a/b/c"
--
makeRelative :: FilePath -> FilePath -> FilePath -- | Is a path relative, or is it fixed to the root? -- -- 
--   Windows: isRelative "path\\test" == True
--   Windows: isRelative "c:\\test" == False
--   Windows: isRelative "c:test" == True
--   Windows: isRelative "c:\\" == False
--   Windows: isRelative "c:/" == False
--   Windows: isRelative "c:" == True
--   Windows: isRelative "\\\\foo" == False
--   Windows: isRelative "\\\\?\\foo" == False
--   Windows: isRelative "\\\\?\\UNC\\foo" == False
--   Windows: isRelative "/foo" == True
--   Windows: isRelative "\\foo" == True
--   Posix:   isRelative "test/path" == True
--   Posix:   isRelative "/test" == False
--   Posix:   isRelative "/" == False
--
-- -- According to [1]: -- -- isRelative :: FilePath -> Bool -- | 
--   not . isRelative
--
-- -- 
--   isAbsolute x == not (isRelative x)
--
isAbsolute :: FilePath -> Bool -- | Is a FilePath valid, i.e. could you create a file like it? This -- function checks for invalid names, and invalid characters, but does -- not check if length limits are exceeded, as these are typically -- filesystem dependent. -- -- 
--            isValid "" == False
--            isValid "\0" == False
--   Posix:   isValid "/random_ path:*" == True
--   Posix:   isValid x == not (null x)
--   Windows: isValid "c:\\test" == True
--   Windows: isValid "c:\\test:of_test" == False
--   Windows: isValid "test*" == False
--   Windows: isValid "c:\\test\\nul" == False
--   Windows: isValid "c:\\test\\prn.txt" == False
--   Windows: isValid "c:\\nul\\file" == False
--   Windows: isValid "\\\\" == False
--   Windows: isValid "\\\\\\foo" == False
--   Windows: isValid "\\\\?\\D:file" == False
--   Windows: isValid "foo\tbar" == False
--   Windows: isValid "nul .txt" == False
--   Windows: isValid " nul.txt" == True
--
isValid :: FilePath -> Bool -- | Take a FilePath and make it valid; does not change already valid -- FilePaths. -- -- 
--   isValid (makeValid x)
--   isValid x ==> makeValid x == x
--   makeValid "" == "_"
--   makeValid "file\0name" == "file_name"
--   Windows: makeValid "c:\\already\\/valid" == "c:\\already\\/valid"
--   Windows: makeValid "c:\\test:of_test" == "c:\\test_of_test"
--   Windows: makeValid "test*" == "test_"
--   Windows: makeValid "c:\\test\\nul" == "c:\\test\\nul_"
--   Windows: makeValid "c:\\test\\prn.txt" == "c:\\test\\prn_.txt"
--   Windows: makeValid "c:\\test/prn.txt" == "c:\\test/prn_.txt"
--   Windows: makeValid "c:\\nul\\file" == "c:\\nul_\\file"
--   Windows: makeValid "\\\\\\foo" == "\\\\drive"
--   Windows: makeValid "\\\\?\\D:file" == "\\\\?\\D:\\file"
--   Windows: makeValid "nul .txt" == "nul _.txt"
--
makeValid :: FilePath -> FilePath