[Haskell-cafe] Infinite grid

Hello, I would like to construct an infinite two-dimensional grid of nodes, where a node looks like this:

data Node = Node { north :: Node , east :: Node , south :: Node , west :: Node }

in such a way that for every node n in the grid it doesn't matter how I travel to n, I always end up in the same memory location for that node. I suspect another way of saying that is that

let f = f . north . east . south . west in f origin

should run in constant space. I hope this makes the problem clear. :-) How do I do this? Thanks in advance, Martijn.