Regarding configurable tiling, a simple strategy would be to have user-specified tiling functions available from Config.hs, of the type tile :: Rational -> Rectangle -> [Window] -> [(Window, Rectangle)] type Tiler =Rational -> Rectangle -> [Window] -> [(Window, Rectangle)] so, myTile :: [Tiler] myTile = [someTileAlgo ,someOtherAlgo ] These functions are then added to the list of algos to cycle through in mod-space, and would allow custom pure functions. David, I suspect you actually want 'tile' to live in X, so you can do window name lookups and so on? Other than generalising the type a bit, how does this sound, as an approach to extending the tiling algo set with custom user-written methods. -- Don