In the process of forking Xmonad, it was discovered that a lot of work would need to be done in getting a Haskell compositor working. Currently, the compositor is being worked on using Tiny-wlhs: A Haskell-Driven Wayland Compositor (Seeking Contributors!)
tiny-wlhs began as an experiment to explore Haskell bindings for wlroots. We took the simple tinywl C compositor and turned it into a Haskell-controlled shared library. This approach lets us incrementally port C code to Haskell while keeping a working window manager. The immediate feedback from a functional compositor is invaluable during development and provides something solid to work with. You can find the project on GitHub: https://github.com/l-Shane-l/tiny-wlhs 25