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Speed up foldMapA.

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Some research in https://github.com/fused-effects/diffused-effects/pull/1
revealed that GHC sometimes fails to optimize newtype-unwrappers of
the foldMapA style sufficiently, and that you get better Core if you
rub some `coerce` on it. Since we use `foldMapA` in a lot of places,
this should have a positive impact.
This commit is contained in:
Patrick Thomson 2019-09-20 16:44:44 -04:00
parent af35b2225a
commit 8bf42329a4
1 changed files with 7 additions and 2 deletions
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9
src/Prologue.hs
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@ -1,4 +1,5 @@
{-# LANGUAGE UndecidableInstances #-} {-# LANGUAGE UndecidableInstances #-}
{-# OPTIONS_GHC -fplugin=DumpCore #-}
module Prologue module Prologue
( module X ( module X
, eitherM , eitherM
@ -66,8 +67,8 @@ import GHC.Stack as X
-- | Fold a collection by mapping each element onto an 'Alternative' action. -- | Fold a collection by mapping each element onto an 'Alternative' action.
foldMapA :: (Alternative m, Foldable t) => (b -> m a) -> t b -> m a foldMapA :: (Alternative m, Foldable t) => (b -> m a) -> t b -> m a
foldMapA f = getAlt . foldMap (Alt . f) foldMapA f = getAlt #. foldMap (Alt #. f)
{-# INLINE foldMapA #-}
maybeLast :: Foldable t => b -> (a -> b) -> t a -> b maybeLast :: Foldable t => b -> (a -> b) -> t a -> b
maybeLast b f = maybe b f . getLast . foldMap (Last . Just) maybeLast b f = maybe b f . getLast . foldMap (Last . Just)
@ -84,3 +85,7 @@ maybeM f = maybe f pure
eitherM :: Applicative f => (a -> f b) -> Either a b -> f b eitherM :: Applicative f => (a -> f b) -> Either a b -> f b
eitherM f = either f pure eitherM f = either f pure
{-# INLINE eitherM #-} {-# INLINE eitherM #-}
(#.) :: Coercible b c => (b -> c) -> (a -> b) -> (a -> c)
(#.) _ = coerce
{-# INLINE (#.) #-}