Henning Thielemann
I even plead for an abstract data type FilePath which supports operations like 'enter a directory', 'go one level higher' and so on.
Beware of Common Lisp history: http://www.gigamonkeys.com/book/practical-a-portable-pathname-library.html "As we discussed in chapter TK, Common Lisp provides an abstraction, the pathname, that is supposed to insulate us from the details of how different OS's and file systems name files. However the gods of abstraction give and they take away. While, with a bit of care, pathnames can be used to write code that will be portable between different OS's it can, ironically, be quite tricky to write pathname code that that will be portable between different Common Lisp implementations on the *same* OS. The root of the problem is that the pathname abstraction was designed to represent file names on a wide variety of file systems. The set of file systems still in general use at the time Common Lisp was being standardized was much more variegated than the set of file systems that are commonly used now. Unfortunately, by making pathnames abstract enough to account for a wide variety of file systems, Common Lisp's designers left implementors with a fair number of choices to be made when mapping the pathname abstraction onto a particular file system. Consequently different implementors, each implementing the pathname abstraction for the same file system, by making different choices at a few key junctions, could end up with conforming implementations that nonetheless provide different behavior for several of the main pathname-related functions." -- __("< Marcin Kowalczyk \__/ qrczak@knm.org.pl ^^ http://qrnik.knm.org.pl/~qrczak/