map f (x:xs) = f x : (map f xs)
map f [] = []

foldr f e (x:xs) = f x (foldr f e xs)
foldr f e [] = e


add l m = ifthenelse (fst3 

map f l = ifthenelse (fst3 l) (append (f (snd3 l)) (map f (thd3 l))) (emptList)


emptList = 3pair false id id
append x l = 3pair true x l