gistfile1.hs

treeSeq :: (a -> [a]) -> a -> [a]
treeSeq children root = root : concatMap (treeSeq children) (children root)

data Tree a = Leaf a 
            | Branch (Tree a) (Tree a)
            deriving (Show, Eq)

children :: Tree a -> [Tree a]
children (Leaf a) = []
children (Branch x y) = [x, y]

--  treeSeq children $ Branch (Leaf 1) (Branch (Leaf 2) (Leaf 3))
--  [Branch (Leaf 1) (Branch (Leaf 2) (Leaf 3)),
--   Leaf 1, Branch (Leaf 2) (Leaf 3), Leaf 2, Leaf 3]