On 30 March 2011 10:20, Tako Schotanus
http://www.haskell.org/pipermail/libraries/2009-August/012493.html I took from this discussion that FilePath really should be a pair of the actual filename ByteString, and the printable String (decoded from the ByteString, with encoding specified by the user's locale). The conversion from ByteString to String (and vice versa) is not guaranteed to be lossless, so you need to remember both.
My understanding is that the ByteString is the one "source of truth" about what the file is called, and you can derive the String from that by assuming some encoding, which is what I proposed in my earlier message. I guess that as an optimisation you could cache the String decoded with a particular encoding as well, but to my mind it's not obviously worth it.
I'm not sure that I agree with that. Why does it have to be loss-less? The problem, more likely, is the fact that FilePath is just a simple string. Maybe we should go the way of Java where cross-platform file access is based upon a File (or the new Path) type?
An opaque Path type has been discussed before and would indeed help a lot, but it would break backwards compatibility in a fairly major way. It might be worth it, though. Max