Does anyone have any advice for optimizing the code, below? Currently, the profiling results look like this: COST CENTRE MODULE %time %alloc runFilter Filter 90.9 41.0 convT Filter 9.1 58.6 Thanks for any help! -db 11 data FilterState a = FilterState { 12 as :: [a] -- transfer function denominator coefficients 13 , bs :: [a] -- transfer function numerator coefficients 14 , taps :: [a] -- current delay tap stored values 15 } deriving (Show) 16 17 type Kernel a = (a, FilterState a) -> (a, FilterState a) 18 19 -- FILTER KERNELS 20 -- Time domain convolution filter (FIR or IIR), 21 -- expressed in direct form 2 22 convT :: (Fractional a) => Kernel a 23 convT (x, s) = 24 let wk = (x - sum [a * t | (a, t) <- zip (tail $ as s) (taps s)]) / head (as s) 25 newTaps = wk : init (taps s) 26 s' = s {taps = newTaps} 27 y = sum [b * w | (b, w) <- zip (bs s) (wk : taps s)] 28 in (y, s') 29 30 -- FILTER APPLICATION 31 runFilter :: Kernel a -> FilterState a -> [a] -> IO ([a], FilterState a) 32 runFilter f s0 [] = do 33 return ([], s0) 34 runFilter f s0 (x:xs) = do 35 (y, s') <- return (f (x, s0)) 36 (ys, s) <- runFilter f s' xs 37 return (y:ys, s)