Mutually recursive structures

Timothy Docker writes:

[...] How can I do this in Haskell? If I don't have mutable references, I figure that I must need to use laziness in some way, perhaps similar to how I would build an infinite structure.

http://www.mail-archive.com/haskell@haskell.org/msg06321.html I have nothing to add to that explanation, so will conserve bandwidth by