29 Dec
2005
29 Dec
'05
7:42 a.m.
David Roundy wrote:
stats elems = foldl add_elem Map.empty elems add_elem m x = Map.insertWith (+) x 1 m
main = print $ stats $ take 1000000 $ repeat 1
This program has a space leak and runs out of stack space. I'm guessing that I'm being bit here by an unnatural amount of laziness in Map.insertWith, but I can't see how to fix this. :( I'm sure it's something elementary...
try: stats = foldl' add_elem Map.empty add_elem m x = myinsertWith (+) x 1 m myinsertWith f k v m = case Map.lookup k m of Nothing -> Map.insert k v m Just w -> let r = f v w in r `seq` Map.insert k r m main = print $ stats $ take 1000000 $ repeat 1