Merge pull request #99 from haskell/fuse-list-instance

Let the list instance fuse
haskell · Jul 26, 2023 · ec7de61 · ec7de61
2 parents 72a665c + c78d703
commit ec7de61
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diff --git a/Control/DeepSeq.hs b/Control/DeepSeq.hs
@@ -558,10 +558,8 @@ instance NFData a => NFData [a] where rnf = rnf1
 
 -- | @since 1.4.3.0
 instance NFData1 [] where
-  liftRnf r = go
-   where
-    go [] = ()
-    go (x : xs) = r x `seq` go xs
+  liftRnf f = foldr (\x r -> f x `seq` r) ()
+  {-# INLINABLE liftRnf #-}
 
 -- | @since 1.4.0.0
 instance NFData a => NFData (ZipList a) where rnf = rnf1

diff --git a/changelog.md b/changelog.md
@@ -8,6 +8,8 @@
     ([#95])(https://github.com/haskell/deepseq/pull/95)
   * Drop support for GHC < 8.6
     ([#94](https://github.com/haskell/deepseq/pull/94))
+  * List fusion in `instance NFData [a]` reduces allocations
+    ([#99](https://github.com/haskell/deepseq/pull/99))
 
 ## 1.4.8.1