This is more an aesthetics question, I have a simple opengl application that has a singleton like object I need to pass around to the display loop and possibly to the keyboard action handler. (pseudo code) data SimpleMech = SimpleMech { mechPos :: !MVector, mechRot :: !MVector } deriving (Read) mainMech = initMech (0, 0, 0) (0, 0, 0) mainMechRef <- newIORef(mainMech) displayCallback $= displayGameLoop mainMechRef rotateMech :: (Double, SimpleMech) -> SimpleMech rotateMech (angle, mech) = -- Calculate a new rotation let (xrot,yrot,zrot) = (mechRot mech) newyrot = newyrot + angle in SimpleMech { mechRot = (xrot, newyrot, zrot), mechPos = (mechPos mech) } displayGameLoop mechRef = do mech <- get mechRef mechRef $= (rotateMech (0.1, mech)) ... ... For some reason in that code above, the "mechRef" doesnt update the value I want to change. It is like I am getting an instance of the initial valyue back. Also, when I use writeIORef, eg writeIORef mechRef (rotateMech (0.1, mech) I get stack overflow exceptions. The displayGameLoop will get called an infinite amount of times, so I think I have to be careful there. But I wonder why the reference isn't getting updated? Is this an approach you would take, eg passing "mechRef" around, a singleton game object. -- Berlin Brown [berlin dot brown at gmail dot com]