8ac1ad1 · streamly · git.iko.soy

git.iko.soy/streamly

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Implement nub as Fold

8ac1ad1Ranjeet Kumar Ranjan4 years ago

benchmark/Streamly/Benchmark/Data/Fold.hs+1

compare with master

unifiedsplit

@@ -294,6 +294,7 @@ o_1_space_serial_elimination value =

294 , benchIOSink value "drainBy" (S.fold (FL.drainBy return))

295 , benchIOSink value "drainN" (S.fold (FL.drainN value))

296 , benchIOSink value "last" (S.fold FL.last)

297+ , benchIOSink value "nub" (S.fold FL.nub)

297 , benchIOSink value "length" (S.fold FL.length)

298 , benchIOSink value "length" (S.fold FL.length)

298 , benchIOSink value "top" (S.fold $ FL.top 10)

299 , benchIOSink value "top" (S.fold $ FL.top 10)

299 , benchIOSink value "bottom" (S.fold $ FL.bottom 10)

300 , benchIOSink value "bottom" (S.fold $ FL.bottom 10)

core/src/Streamly/Internal/Data/Fold.hs+25−1

@@ -280,6 +280,7 @@ module Streamly.Internal.Data.Fold

280 , finish

281 , top

282 , bottom

283+ , nub

283

284

284 -- * Deprecated

285 -- * Deprecated

285 , sequence

286 , sequence

@@ -335,7 +336,7 @@ import Streamly.Internal.Data.Fold.Type

335-- >>> :set -package streamly

336-- >>> :set -package streamly

336-- >>> import Prelude hiding (break, map, span, splitAt)

337-- >>> import Prelude hiding (break, map, span, splitAt)

337-- >>> import qualified Streamly.Prelude as Stream

338-- >>> import qualified Streamly.Prelude as Stream

338−-- >>> import qualified Streamly.Internal.Data.Stream.IsStream as Stream (parse, foldMany)

339+-- >>> import qualified Streamly.Internal.Data.Stream.IsStream as Stream (catMaybes, parse, foldMany)

339-- >>> import qualified Streamly.Data.Fold as Fold

340-- >>> import qualified Streamly.Data.Fold as Fold

340-- >>> import qualified Streamly.Internal.Data.Fold as Fold

341-- >>> import qualified Streamly.Internal.Data.Fold as Fold

341-- >>> import qualified Streamly.Internal.Data.Fold.Type as Fold

342-- >>> import qualified Streamly.Internal.Data.Fold.Type as Fold

@@ -2562,3 +2563,26 @@ top = topBy $ flip compare

2562{-# INLINE bottom #-}

2563{-# INLINE bottom #-}

2563bottom :: (MonadIO m, Storable a, Ord a) => Int -> Fold m a (MA.Array a)

2564bottom :: (MonadIO m, Storable a, Ord a) => Int -> Fold m a (MA.Array a)

2564bottom = topBy compare

2565bottom = topBy compare

2566+

2567+-- | Delete the duplicate elements from the stream while scanning.

2568+-- It returns (Just a) for new element and Nothing for duplicates ones.

2569+--

2570+-- >>> stream = Stream.fromList [1::Int, 1, 2, 3, 4, 4, 5, 1, 5, 7]

2571+-- >>> Stream.toList $ Stream.catMaybes $ Stream.postscan Fold.nub stream

2572+-- [1,2,3,4,5,7]

2573+--

2574+-- /Pre-release/

2575+{-# INLINE nub #-}

2576+nub :: (MonadIO m, Ord a) => Fold m a (Maybe a)

2577+nub = Fold step initial extract

2578+

2579+ where

2580+

2581+ initial = return $ Partial (Set.empty, Nothing)

2582+

2583+ step (set, _) x = do

2584+ if Set.member x set

2585+ then return $ Partial (set, Nothing)

2586+ else return $ Partial (Set.insert x set, Just x)

2587+

2588+ extract = return . snd

test/Streamly/Test/Data/Fold.hs+9

@@ -670,6 +670,14 @@ top = topBy True

670bottom :: Property

671bottom = topBy False

672

673+nub :: Property

674+nub = monadicIO $ do

675+ vals <- Stream.toList

676+ $ Stream.catMaybes

677+ $ Stream.postscan F.nub

678+ $ Stream.fromList [1::Int, 1, 2, 3, 4, 4, 5, 1, 5, 7]

679+ assert (vals == [1, 2, 3, 4, 5, 7])

680+

673moduleName :: String

681moduleName :: String

674moduleName = "Data.Fold"

682moduleName = "Data.Fold"

675

683

@@ -720,6 +728,7 @@ main = hspec $ do

720 prop "or" Main.or

728 prop "or" Main.or

721 prop "top" Main.top

729 prop "top" Main.top

722 prop "bottom" Main.bottom

730 prop "bottom" Main.bottom

731+ prop "nub" Main.nub

723

732

724 -- Combinators

733 -- Combinators

725

734