System.Directory (was RE: Proposal for a new I/O library design)

[Wolfgang Thaller]

>> pathSeparator :: Char
>> '\\' on Windows, '/' on unices, ':' (I believe) on macs, etc...

Used to be ':' in Classic MacOS, and there are still some old routines 
in Apple's Carbon library that take ':'-separated paths. However, Apple 
always insisted that Pathnames should only be used for display 
purposes, mostly because a pathname did not always uniquely identify a 
file (!).
Mac OS X uses "normal" unix-style paths for everything that concerns 
us. Also, the "Classic" Mac-style paths had different semantics (no "." 
or "..", etc.), so treating them would have been more difficult than 
just using a different separator. Fortunately, they're a thing of the 
past.

>> directorySeparator :: Char
>> ';' on Windows, ':' on unices, i have no idea on macs

As there was no command line, no PATH, and no textual config files on 
classic Mac OS, there is no mac-specific directory separator, so it's 
':'.
  (although I think that stealing yet another character from

>
>> isCaseSensitive :: Bool
>> False on Windows, True on (all?) unices, i have no idea on macs

It's not that easy. Case sensitivity is a property of a file system, 
not of the operating system.
So if you mount a Windows or Mac OS volume on a Linux system, the 
filenames on that volume will still be case-insensitive (but 
case-preserving).
On Mac OS X, the default file system type is HFS+ (a.k.a. Mac OS 
Extended), which is case insensitive, but you can also choose UFS (case 
sensitive). You could also have both, on two partitions.
Of course, "False" for Windows and MacOS, "True" for everything else is 
a reasonable guess, but you can't rely on it.
Right now I have no idea how to implement something like

isCaseSensitive :: FilePath -> IO Bool

which would determine whether a specific path would be case sensitive. 
Maybe it's worth the effort to think about it.

> given just these, i think we'd all be a lot happier.

I agree. If the last one can be implemented properly, that is.

Cheers,

Wolfgang