breadth first search (bfs) for multiway trees implemented in haskell

multiway_trees_bfs.hs

data Tree a = Node a [Tree a]


traverseBF :: Tree a -> Tree a
traverseBF tree = tbf tree
    where
        tbf (Node x []) = Node x []
        tbf (Node x xs) =  Node x (map tbf $ xs)
        nodeValue (Node a _) = a
        nodes (Node _ []) = []
        nodes (Node _ xs) = xs



instance (Show a) => Show (Tree a) where
    show tree = show' 0 tree
        where show' n t = 
                let
                    tabs = (replicate n '\t')
                    showNext x = '\n' : show' (n+1) x
                in
                case t of 
                    (Node x []) -> tabs ++ show x
                    (Node x xs) -> tabs ++ show x ++ concatMap showNext xs



createTree = 
    Node 'A'[
        Node 'B'[
            Node 'C' [],
            Node 'D' []
        ],
        Node 'E' [
            Node 'F' [],
            Node 'G' [
                Node 'H' [
                    Node 'I' []
                ]
            ]
        ]
    ]

main = do
    let 
        t = createTree
    print (traverseBF t)