diff options
| -rw-r--r-- | libraries/base/GHC/List.hs | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/libraries/base/GHC/List.hs b/libraries/base/GHC/List.hs index a712f9e4be..fcc89d3f8f 100644 --- a/libraries/base/GHC/List.hs +++ b/libraries/base/GHC/List.hs @@ -84,8 +84,15 @@ last [x] = x last (_:xs) = last xs last [] = errorEmptyList "last" #else --- use foldl to allow fusion -last = foldl (\_ x -> x) (errorEmptyList "last") +-- Use foldl to make last a good consumer. +-- This will compile to good code for the actual GHC.List.last. +-- (At least as long it is eta-expaned, otherwise it does not, #10260.) +last xs = foldl (\_ x -> x) lastError xs +{-# INLINE last #-} +-- The inline pragma is required to make GHC remember the implementation via +-- foldl. +lastError :: a +lastError = errorEmptyList "last" #endif -- | Return all the elements of a list except the last one. |