Hello algorithms, Sunday, August 6, 2006, 1:50:42 PM, you wrote:
listFoldr f y Nil = y listFoldr f y (Cons x xs) = f x (foldr f z xs)
this is definitely wrong - using foldr instead of listFoldr and 'z' appearing from nowhere :)
listFoldr f y Nil = y listFoldr f y (Cons x xs) = f y (listFoldr f (f y x) xs)
y is a final value that should be used only at the last point. for example: sum = foldr1 (+) 0 sum [1,2,3] = 1+2+3+0 so, 'y' in second statement for listFoldr should be passed to recursive call of listFoldr (so it can be eventually used by the first statemnet) but not used in call to f. second, your definition calls 'f' two times, so the final result will be something like: sum [1,2,3] = 1+2+3+(1+2+3+0) (you can try) -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com