free.hs

type Double a = (a, a)
data DoubleTree a = DLeaf a | DBranch (DoubleTree a, DoubleTree a)

type List a = [a]
data ListTree a = LLeaf a | LBranch [ListTree a]

type Maybe a
data MaybeTree a = MLeaf a | MBranch (Maybe (MaybeTree a))
                 = MLeaf a | MJust (MaybeTree a) | MNothing
              
data Tree a = Leaf a | Branch (Tree a, Tree a)
data TreeTree a = TLeaf a | TBranch (Tree (TreeTree a))
                = TLeaf a | TBranchLeaf (TreeTree a) | TBranchBranch (TreeTree a) (TreeTree a)
                
type Reader a = ((->) a)
type ReaderInt a = (a -> Int)
data ReaderIntTree a = RILeaf a | RIBranch (ReaderInt (ReaderIntTree a))
                     = RILeaf a | RIBranch ((ReaderIntTree a) -> Int)