{-# LANGUAGE CPP #-}
module Tree where

import Control.Parallel
import Control.Parallel.Strategies

data Tree a = Branch a [Tree a] deriving Show

repTree :: (a->[a]) -> (a->[a])-> a -> (Tree a)
repTree f g a = Branch a (map (repTree g f) (f a))

#define SEQ

#ifndef SEQ

mapTree :: (a -> b) -> Tree a -> Tree b
mapTree f (Branch a l) 
   = fa `par` Branch fa (map (mapTree f) l `using` myParList)
   where fa = f a

#else  {- SEQ -}

mapTree :: (a -> b) -> (Tree a) -> (Tree b)
mapTree f (Branch a l) = Branch (f a) (map (mapTree f) l)

#endif

myParList [] = ()
myParList (x:xs) = x `par` myParList xs

mySeqList [] = ()
mySeqList (x:xs) = x `seq` mySeqList xs

parTree :: Int -> Tree a -> ()
parTree 0 (Branch a xs) = ()
parTree n (Branch a xs) = a `par` mySeqList (map (parTree (n-1)) xs)

prune :: Int -> (Tree a) -> (Tree a)
prune 0 (Branch a l) = Branch a []
prune n (Branch a l) = Branch a (map (prune (n-1)) l)