I usually use a manually written loop, but you can use Data.Vector for this
and it should fuse.
John L.
On Apr 26, 2014 2:41 PM, "Niklas Hambüchen"
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 _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe