On Fri, Sep 28, 2012 at 9:16 PM, Herbert Valerio Riedel
I don't know whether this might the reason (or whether it is relevant at all for the API at hand) but you can't implement this function properly w/o turning it into an IO action, since you need to be able to introspect the filesystem, because under POSIX at least, you can easily construct a filesystem, which exhibits the following confusing behaviour:
I have two comments on this behaviour: 1. "confusing" is not the same as "wrong" 2. surely this issue can be avoided by using something like System.Directory.canoncalizePath before calling makeRelative. I think doing things that way would separate the pure and IO parts of the algorithm much better, and allow users to ignore the possibility of symlinks when that was appropriate for their use.