On 9/30/12 10:24 AM, Ben Millwood wrote:
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.
Indeed. While it's important to be able to capture correct POSIX behavior, there's also plenty of room for legitimate uses of naive relative paths. In particular, the former is more important when accessing the filesystem, whereas the latter is more important when generating files[1]. So long as the documentation includes das blinkenlights, to ensure that users know which behavior they're getting, I think it's fine to offer the naive implementation. If folks consider it "unsafe" enough to warrant name changes, we could always: canoncalizePath :: Path -> IO Path naiveMakeRelative :: Path -> Path -> Path makeRelative x y = do x <- canoncalizePath x y <- canoncalizePath y return $! naiveMakeRelative x y [1] Because you know the filesystem structure you'll be generating, so you know whether this will be an issue. And because the files you'll be generating don't yet exist and so can't be cannonicalized, as others have mentioned. -- Live well, ~wren