Re: [Haskell-cafe] Mapping over multiple values of a list at once?

Hi Max How about a paramorphism? slideAvg3 :: [Int] -> [Int] slideAvg3 = para phi [] where phi x ((y:z:_),acc) = average3 x y z : acc phi x (_,acc) = acc -- helpers -- paramorphism (generalizes catamorphism (fold)) para :: (a -> ([a], b) -> b) -> b -> [a] -> b para phi b [] = b para phi b (x:xs) = phi x (xs, para phi b xs) average3 :: Int -> Int -> Int -> Int average3 a b c = round $ (fromIntegral $ a+b+c)/3 I haven't tested for efficiency though. Best wishes Stephen 2009/8/27 Max Rabkin :

However, we don't really need the sliding windows themselves, just the sliding sum. There might be a slightly more efficient way to do that, but I'll leave it as an exercise for you or somebody else.

--Max