Haskell Mutually Recursive Types

A type that depends on another type that depends on the current type

Example

A tree with branches that contain the values.

data Tree a = Empty
			| Node (Branch a) (Branch a)
data Branch a = Branch a (Tree a)
 
listTree :: Tree a -> [a]
listTree Empty = []
listTree (BNode l r) = (listBranch l) ++ (listBranch r)
 
listBranch :: Branch a -> [a]
listBranch (Branch v t) = v : listTree t