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