Pathlib provides an API for parsing and manipulating *tree* paths, represented as bytestrings. The path types come with witnesses (similar to the pathtype package) for improved type safety, although they are optional and disabled by the default interface (Data.Path) since they can be somewhat inconvenient. The safe interface is exported by Data.Path.Witnessed.

A number of path combinators is provided (/>, <., +/+), as well as a few selectors (especially well suited for use as view patterns or pattern guards). All paths are kept normalised and this invariant is maintained throughout the API, providing both nicer path strings and easier equality checking.

The API is limited to trees, which means that POSIX systems that allow arbitrary graphs in the filesystem, through symlinks, are not supported 100 % correctly: the .. components in paths are, in path parsing and manipulation, treated as parent directory of the *path* and the actual .. hardlinks in the filesystem are not consulted. This is consistent with the behaviour of cd .. in shells, but inconsistent with how paths are resolved by the operating system.