a4464a8 · streamly · git.iko.soy

git.iko.soy/streamly

Fix a bug in zipWithM rule that causes effects to run only once.

commita4464a87961f441b1661a5defe2aff42790b8347 authorPranay Sashank <pranaysashank@gmail.com> dateFri 2 Aug 2019, 01:34 (7 years ago) parentde908d6

1 file changed+3−1

unifiedsplit

src/Streamly/Streams/StreamD.hs+3−1

@@ -11,6 +11,7 @@

1111{-# LANGUAGE ViewPatterns #-}

1212{-# LANGUAGE RankNTypes #-}

1313{-# LANGUAGE MagicHash #-}

14+{-# LANGUAGE TypeApplications #-}

1415

1516#include "inline.hs"

1617

@@ -255,6 +256,7 @@ import Control.Monad.Catch (MonadCatch)

255256import Control.Monad.IO.Class (MonadIO(..))

256257import Control.Monad.Trans (MonadTrans(lift))

257258import Data.Bits (shiftR, shiftL, (.|.), (.&.))

259+import Data.Functor.Identity (Identity)

258260import Data.Maybe (fromJust, isJust)

259261import Data.Word (Word32)

260262import Foreign.Ptr (Ptr)

@@ -2353,7 +2355,7 @@ zipWithM f (Stream stepa ta) (Stream stepb tb) = Stream step (ta, tb, Nothing)

23532355 Stop -> return Stop

23542356

23552357{-# RULES "zipWithM xs xs"

2356− forall f xs. zipWithM f xs xs = mapM (\x -> f x x) xs #-}

2358+ forall f xs. zipWithM @Identity f xs xs = mapM (\x -> f x x) xs #-}

23572359

23582360{-# INLINE zipWith #-}

23592361zipWith :: Monad m => (a -> b -> c) -> Stream m a -> Stream m b -> Stream m c