Glynn Clements writes:
Well, there is a sort-of canonic version for every path; on most Unix systems the function realpath(3) will find it. My interpretation is that two paths are equivalent iff they point to the same target.
I think that any definition which includes an "iff" is likely to be overly optimistic.
I see your point. I guess it comes down to how much effort is put into implementing a realpath() derivate in Haskell.
Even so, you will need to make certain assumptions. E.g. older Unices would allow root to replace the "." and ".." entries; you probably want to assume that can't happen.
My take on things is that it is hopeless to even try and cover all this weird behavior. I'd like to treat paths as something abstract. What I'm aiming for is that my library can be used to manipulate file paths as well as URLs, namespaces, and whatnot else; so I'll necessarily lose some functionality that an implementation specifically designed for file paths could provide. If you want to be portable, you cannot use any esoteric functionality anyway.
There are also issues of definition, e.g. is "/dev/tty" considered "equivalent" to the specific "/dev/ttyXX" device for the current process?
No, because the paths differ. ;-) Peter