Awesome haskellers, I am coding up a little function that aggregates "ask orders" in a currency exchange. Another way to look at it, is that the function takes as input a histogram or fdf (in list format) and outputs the cumulative distribution cdf (also in list format). So we are kind of "integrating" the input list. When given a list of asks in order of increasing price, the function returns a list of points in the graph of the total supply curve. Here's an example: asks: returned list: [ (Price 42, Volume 0.5), [ (Price 21, Volume 0.5), (Price 50, Volume 1 ), (Price 21+50=71, Volume 1.5), (Price 55, Volume 0.2)] (Price 21+50+11=82,Volume 1.7)] the returned list gives us the total supply curve (price = y-axis, quantity/volume = x-axis, so the order is flipped) Summarizing * We're adding up the volumes. The last volume on the list is the total volume available for sale. * We calculate the total amount to be paid to buy the current volume (for each item in the list). I have written up a simple function to do this: aggregate :: Num a => [(a,a)] -> [(a,a)] aggregate xs = aggregate' 0 0 xs aggregate' :: Num a => a -> a -> [(a,a)] -> [(a,a)] aggregate' _ _ [] = [] aggregate' accX accY ((x,y):ls) = let accX' = accX + x * y accY' = accY + y in (accX',accY') : aggregate' accX' accY' ls main = print $ aggregate [(42,0.5),(50,1),(55,0.2)] However, this does not look very good to me and it feels like I'm reinventing the wheel. Question: Is there a better Haskell way to do this? I'm really anal about making it easy to read. Thanks! Dimitri