1 module Tree where
    2 
    3 data Tree a = Branch a [Tree a] deriving Show{-was:Text-}
    4 
    5 repTree :: (a->[a]) -> (a->[a])-> a -> (Tree a)
    6 repTree f g a = Branch a (map (repTree g f) (f a))
    7 
    8 
    9 mapTree :: (a -> b) -> (Tree a) -> (Tree b)
   10 mapTree f (Branch a l) = Branch (f a) (map (mapTree f) l)
   11 
   12 prune :: Int -> (Tree a) -> (Tree a)
   13 prune 0 (Branch a l) = Branch a []
   14 --should be:prune (n+1) (Branch a l) = Branch a (map (prune n) l)
   15 prune n (Branch a l) | n < 0     = error "Tree.prune: < 0"
   16                      | otherwise = Branch a (map (prune (n-1)) l)
   17