git.iko.soy/streamly
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Add a "foldFilter" combinator for folds
commit8dabc2ec8af045cd774caec5f43d855d380550f7 authorHarendra Kumar <harendra@composewell.com> dateMon 21 Mar 2022, 21:03 (5 years ago) parent616f034
3 files changed+64−3
compare with master
unifiedsplit
benchmark/Streamly/Benchmark/Data/Fold.hs+24−2 core/src/Streamly/Internal/Data/Fold.hs+38 core/src/Streamly/Internal/Data/Fold/Type.hs+2−1
benchmark/Streamly/Benchmark/Data/Fold.hs+24−2
@@ -27,7 +27,7 @@ import qualified Streamly.Prelude as S
2727
2828import Gauge
2929import Streamly.Benchmark.Common
30−import Prelude hiding (all, any, take, unzip, sequence_)
30+import Prelude hiding (all, any, take, unzip, sequence_, filter)
3131
3232-- We need a monadic bind here to make sure that the function f does not get
3333-- completely optimized out by the compiler in some cases.
@@ -78,6 +78,25 @@ sequence_ value =
7878 {-# INLINE f #-}
7979 f m k = FL.concatMap (const k) m
8080
81+-------------------------------------------------------------------------------
82+-- Filter
83+-------------------------------------------------------------------------------
84+
85+{-# INLINE filter #-}
86+filter :: Monad m => Int -> SerialT m Int -> m ()
87+filter _ = IP.fold (FL.filter even FL.drain)
88+
89+{-# INLINE foldFilter #-}
90+foldFilter :: Monad m => Int -> SerialT m Int -> m ()
91+foldFilter _ = IP.fold (FL.foldFilter (FL.satisfy even) FL.drain)
92+
93+{-# INLINE foldFilter2 #-}
94+foldFilter2 :: Monad m => Int -> SerialT m Int -> m ()
95+foldFilter2 _ =
96+ IP.fold
97+ $ FL.foldFilter (FL.satisfy even)
98+ $ FL.foldFilter (FL.satisfy odd) FL.drain
99+
81100-------------------------------------------------------------------------------
82101-- Splitting by serial application
83102-------------------------------------------------------------------------------
@@ -323,7 +342,10 @@ o_1_space_serial_composition :: Int -> [Benchmark]
323342o_1_space_serial_composition value =
324343 [ bgroup
325344 "composition"
326− [ benchIOSink value "serialWith (all, any)" $ splitAllAny value
345+ [ benchIOSink value "filter even" $ filter value
346+ , benchIOSink value "foldFilter even" $ foldFilter value
347+ , benchIOSink value "foldFilter even, odd" $ foldFilter2 value
348+ , benchIOSink value "serialWith (all, any)" $ splitAllAny value
327349 , benchIOSink value "serial_ (all, any)" $ serial_ value
328350 , benchIOSink value "tee (all, any)" $ teeAllAny value
329351 , benchIOSink value "many drain (take 1)" many
core/src/Streamly/Internal/Data/Fold.hs+38
@@ -132,6 +132,8 @@ module Streamly.Internal.Data.Fold
132132 -- ** Filtering
133133 , filter
134134 , filterM
135+ , foldFilter
136+ , satisfy
135137 , sampleFromthen
136138 -- , ldeleteBy
137139 -- , luniq
@@ -477,6 +479,42 @@ postscan (Fold stepL initialL extractL) (Fold stepR initialR extractR) =
477479
478480 extract = extractR . snd
479481
482+------------------------------------------------------------------------------
483+-- Filters
484+------------------------------------------------------------------------------
485+
486+-- | Convert a predicate into a filtering fold.
487+--
488+-- >>> f = Fold.foldFilter (Fold.satisfy (> 5)) Fold.sum
489+-- >>> Stream.fold f $ Stream.fromList [1..10]
490+-- 40
491+--
492+-- /Pre-release/
493+{-# INLINE satisfy #-}
494+satisfy :: Monad m => (a -> Bool) -> Fold m a (Maybe a)
495+satisfy f = Fold step (return $ Partial ()) (const (return Nothing))
496+
497+ where
498+
499+ step () a = return $ Done $ if f a then Just a else Nothing
500+
501+-- | Use a 'Maybe' returning fold as a filtering scan.
502+--
503+-- >>> f = Fold.foldFilter (Fold.satisfy (> 5)) Fold.sum
504+-- >>> Stream.fold f $ Stream.fromList [1..10]
505+-- 40
506+--
507+-- The above snippet is equivalent to:
508+--
509+-- >>> f = Fold.filter (> 5) Fold.sum
510+-- >>> Stream.fold f $ Stream.fromList [1..10]
511+-- 40
512+--
513+-- /Pre-release/
514+{-# INLINE foldFilter #-}
515+foldFilter :: Monad m => Fold m a (Maybe b) -> Fold m b c -> Fold m a c
516+foldFilter f1 f2 = many f1 (catMaybes f2)
517+
480518------------------------------------------------------------------------------
481519-- Left folds
482520------------------------------------------------------------------------------
core/src/Streamly/Internal/Data/Fold/Type.hs+2−1
@@ -393,6 +393,7 @@ module Streamly.Internal.Data.Fold.Type
393393 )
394394where
395395
396+#include "inline.hs"
396397import Control.Monad ((>=>))
397398import Data.Bifunctor (Bifunctor(..))
398399import Data.Maybe (isJust, fromJust)
@@ -1167,7 +1168,7 @@ filterM f (Fold step begin done) = Fold step' begin done
11671168-- and sent to the original fold, 'Nothing' values are discarded.
11681169--
11691170-- @since 0.8.0
1170−{-# INLINE catMaybes #-}
1171+{-# INLINE_NORMAL catMaybes #-}
11711172catMaybes :: Monad m => Fold m a b -> Fold m (Maybe a) b
11721173catMaybes = filter isJust . lmap fromJust
11731174