On Wed, 21 Apr 2004, Steve Schafer wrote:
runningSum :: (Ord a, Num a) => [a] -> [a] runningSum [] = [] runningSum (i:[]) = i : [] runningSum (i:j:js) = i : runningSum (i+j : js)
this is certainly the same as scanl1 (+)
zipWithSum :: (Ord a, Num a) => [a] -> [(a,a)] zipWithSum xs = zip (runningSum xs) xs
threshold :: (Ord a, Num a) => [a] -> a -> ([(a,a)],[(a,a)]) threshold xs t = let test x = (t >= (fst x)) in span test (zipWithSum xs)
In general you should make the threshold 't' the first argument of your functions, since it will have different values less often than 'xs'.
splitFirst :: (Ord a, Num a) => [a] -> a -> ([a],[a]) splitFirst xs t = let (ys,zs) = threshold xs t in (snd (unzip ys), snd (unzip zs))
splitAll :: (Ord a, Num a) => [a] -> a -> [[a]] splitAll [] _ = [] splitAll xs t = let (ys, zs) = splitFirst xs t in ys : (splitAll zs t)
With swapped arguments of splitFirst and Maybe value you could invoke it with 'unfoldr' in splitAll. Though a recursive algorithm may be more elegant here.