Hi all, Following a little thread on Reddit[1], I'm trying to add rewrite rules to conduit to make some simple usages of `yield` more efficient. I've pushed these changes to a branch on Github[2]. However, I'm not able to fully optimize the following program: import Data.Conduit import qualified Data.Conduit.List as CL main :: IO () main = do x <- mapM_ yield [1..1000] $$ CL.fold (+) 0 print (x :: Int) Ideally, I would like to rewrite the entirety of `mapM_ yield [1..1000]` to `Data.Conduit.List.enumFromTo 1 1000` and thereby avoid the intermediate list. However, whenever I add such a rule, it doesn't fire. Instead, -ddump-rule-firings tells me: Rule fired: Class op enumFromTo Rule fired: mapM_ yield Rule fired: Class op + Rule fired: Class op >>= Rule fired: Class op show Rule fired: eftIntList I'm quite a novice at rewrite rules; can anyone recommend an approach to get my rule to fire first? Thanks, Michael PS: In case you're wondering, the `mapM_ yield` rule turns `mapM_ yield` into `yieldMany`. So ideally, I'd like to have another rule that turns `yieldMany [x..y]` into `Data.Conduit.List.enumFromTo x y`. [1] http://www.reddit.com/r/haskell/comments/sdzmx/many_ways_to_skin_a_conduit/c... [2] https://github.com/snoyberg/conduit/tree/rewrite