How can I run something like scanl on Map.
Say I have Map.fromList [(0, 2), (1, 3), (2, 4)].
How can I get Map.fromList [(0, 2), (1, 5), (2, 9)] so that the values accumulated by summing in keys accending order?
The function I was referring to in my comment was mapAccum:
mapAccum :: (a -> b -> (a, c)) -> a -> Map k b -> (a, Map k c)
ghci> m = M.fromList [(0, 2), (1, 3), (2, 4)]
ghci> M.mapAccum (\x y -> (x + y, x + y)) 0 m
(9,fromList [(0,2),(1,5),(2,9)])
It also returns the final accumulator, so if you don't want that you'll need to call snd on the resulting tuple.