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Optimize "foldl"

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This commit is contained in:
Nikita Volkov 2015-11-21 12:01:32 +03:00
parent 103c80090a
commit 89470ff672
2 changed files with 7 additions and 1 deletions
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2
library/Hasql/Deserialization/Result.hs
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@ -182,7 +182,7 @@ foldl step init rowDes =
maxCols <- LibPQ.nfields result
accRef <- newIORef init
failureRef <- newIORef Nothing
forM_ [0 .. pred (rowToInt maxRows)] $ \rowIndex -> do
forMFromZero_ (rowToInt maxRows) $ \rowIndex -> do
rowResult <- Row.run rowDes (result, intToRow rowIndex, maxCols, integerDatetimes)
case rowResult of
Left x -> writeIORef failureRef (Just (RowError rowIndex x))

6
library/Hasql/Prelude.hs
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@ -8,6 +8,7 @@ module Hasql.Prelude
bug,
bottom,
forMToZero_,
forMFromZero_,
strictCons,
)
where
@ -122,6 +123,11 @@ forMToZero_ :: Applicative m => Int -> (Int -> m a) -> m ()
forMToZero_ !startN f =
($ pred startN) $ fix $ \loop !n -> if n >= 0 then f n *> loop (pred n) else pure ()
{-# INLINE forMFromZero_ #-}
forMFromZero_ :: Applicative m => Int -> (Int -> m a) -> m ()
forMFromZero_ !endN f =
($ 0) $ fix $ \loop !n -> if n < endN then f n *> loop (succ n) else pure ()
{-# INLINE strictCons #-}
strictCons :: a -> [a] -> [a]
strictCons !a b =