diff options
Diffstat (limited to 'compiler/GHC/Utils/Monad.hs')
| -rw-r--r-- | compiler/GHC/Utils/Monad.hs | 14 |
1 files changed, 5 insertions, 9 deletions
diff --git a/compiler/GHC/Utils/Monad.hs b/compiler/GHC/Utils/Monad.hs index 59964b8024..ef254fce63 100644 --- a/compiler/GHC/Utils/Monad.hs +++ b/compiler/GHC/Utils/Monad.hs @@ -10,7 +10,7 @@ module GHC.Utils.Monad , zipWith3M, zipWith3M_, zipWith4M, zipWithAndUnzipM , mapAndUnzipM, mapAndUnzip3M, mapAndUnzip4M, mapAndUnzip5M - , mapAccumLM + , mapAccumLM' , liftFstM, liftSndM , mapSndM , concatMapM @@ -137,21 +137,17 @@ mapAndUnzip5M :: Monad m => (a -> m (b,c,d,e,f)) -> [a] -> m ([b],[c],[d],[e],[f -- See Note [Inline @mapAndUnzipNM@ functions] above. mapAndUnzip5M f xs = unzip5 <$> traverse f xs --- TODO: mapAccumLM is used in many places. Surely most of --- these don't actually want to be lazy. We should add a strict --- variant and use it where appropriate. - --- | Monadic version of mapAccumL -mapAccumLM :: Monad m +-- | Monadic version of mapAccumL, but strict both in state and elements. +mapAccumLM' :: Monad m => (acc -> x -> m (acc, y)) -- ^ combining function -> acc -- ^ initial state -> [x] -- ^ inputs -> m (acc, [y]) -- ^ final state, outputs -mapAccumLM f s xs = +mapAccumLM' f s xs = go s xs where go s (x:xs) = do - (s1, x') <- f s x + (!s1, !x') <- f s x (s2, xs') <- go s1 xs return (s2, x' : xs') go s [] = return (s, []) |