[Haskell-cafe] Examples of Mutually Recursive Types

[Henning Thielemann]

On Sun, 26 Oct 2008, Hugo Pacheco wrote:

> Hi all,
> I have been searching for examples of Haskell "real scenarios" that employ
> mutually recursive datatype definitions.
> Does anyone know some interesting libraries or structures that I could play
> with?

http://darcs.haskell.org/wraxml/src/Data/Tree/BranchLeafTag.hs

Here Elem uses Tree.T and Tree.T uses Elem. Is this what you are looking 
for?