[Haskell-cafe] How to write fast for loops

As you probably now, `forM_ [1..n]` is incredibly slow in Haskell due to lack of list fusion [1]; a manually written loop is 10x faster. How do you people work around this? I keep defining myself something like loop :: (Monad m) => Int -> (Int -> m ()) -> m () loop bex f = go 0 where go !n | n == bex = return () | otherwise = f n >> go (n+1) Is there a function for this somewhere already? Or do you have another way to deal with this problem? Thanks! [1]: https://ghc.haskell.org/trac/ghc/ticket/8763