"Gü?nther Schmidt"
let say I got an unordered lazy list of key/value pairs like
[('a', 99), ('x', 42), ('a', 33) ... ]
and I need to sum up all the values with the same keys.
So far I wrote a naive implementation, using Data.Map, foldl and insertWith.
Data.Map.fromListWith (+)
The building of this map is of course a bottleneck, the successive processing needs to wait until the entire list is eventually consumed the Map is built and flattened again.
Sure this is not an artifact of the laziness of foldl?
Is there another way of doing this, something more "streaming architecture" like?
I don't see how you can do this much better - for a small, fixed set of keys, you could use an (STU) array for the sums, but it depends if the added complexity is worth it. You're already doing a single pass over the data. -k -- If I haven't seen further, it is by standing in the footprints of giants