TwitAA 2012-01-17 18:03:49 [TwitAA 2012-01-17 18:03:49] foldr (+) 0 [1..5] = (1 + (2 + (3 + (4 + (5 + 0))))) foldl (+) 0 [1..5] = (((((0 + 1) + 2) + 3) + 4) + 5)