f393b15 · streamly · git.iko.soy

git.iko.soy/streamly

Add foldOn

commitf393b15fc5310a0bde807919c2b70064f63ea3a0 authorHarendra Kumar <harendra@composewell.com> dateSat 16 Oct 2021, 00:15 (5 years ago) parenta096f77

3 files changed+43−1

compare with master

unifiedsplit

src/Streamly/Internal/Data/Stream/IsStream/Common.hs+15 src/Streamly/Internal/Data/Stream/IsStream/Eliminate.hs+2−1 src/Streamly/Internal/Data/Stream/StreamD/Type.hs+26

src/Streamly/Internal/Data/Stream/IsStream/Common.hs+15

@@ -22,6 +22,7 @@ module Streamly.Internal.Data.Stream.IsStream.Common

2222 , relTimesWith

2323

2424 -- * Elimination

25+ , foldOn

2526 , fold

2627 , fold_

2728

@@ -104,6 +105,7 @@ import Prelude hiding (take, takeWhile, drop, reverse, concatMap, map, zipWith)

104105-- >>> import Streamly.Internal.Data.Stream.IsStream as Stream

105106-- >>> import qualified Streamly.Data.Array.Foreign as Array

106107-- >>> import qualified Streamly.Data.Fold as Fold

108+-- >>> import qualified Streamly.Internal.Data.Fold as Fold

107109-- >>> import qualified Streamly.Data.Unfold as Unfold

108110

109111------------------------------------------------------------------------------

@@ -266,6 +268,19 @@ relTimesWith = fmap snd . timesWith

266268-- Elimination - Running a Fold

267269------------------------------------------------------------------------------

268270

271+-- | We can create higher order folds using 'foldOn'. We can fold a number of

272+-- streams to a given fold efficiently with full stream fusion. For example, to

273+-- fold a list of streams on the same sum fold:

274+--

275+-- >>> concatFold = Prelude.foldl Stream.foldOn Fold.sum

276+--

277+-- >>> fold f = Fold.finish . Stream.foldOn f

278+--

279+-- /Internal/

280+{-# INLINE foldOn #-}

281+foldOn :: Monad m => Fold m a b -> SerialT m a -> Fold m a b

282+foldOn f s = D.foldOn f $ IsStream.toStreamD s

283+

269284-- | Fold a stream using the supplied left 'Fold' and reducing the resulting

270285-- expression strictly at each step. The behavior is similar to 'foldl''. A

271286-- 'Fold' can terminate early without consuming the full stream. See the

src/Streamly/Internal/Data/Stream/IsStream/Eliminate.hs+2−1

@@ -24,6 +24,7 @@ module Streamly.Internal.Data.Stream.IsStream.Eliminate

2424 -- See "Streamly.Internal.Data.Fold".

2525 fold

2626 , fold_

27+ , foldOn

2728

2829 -- * Running a 'Parser'

2930 -- "Streamly.Internal.Data.Parser".

@@ -161,7 +162,7 @@ import Streamly.Internal.Control.Concurrent (MonadAsync)

161162import Streamly.Internal.Data.Parser (Parser (..))

162163import Streamly.Internal.Data.SVar (defState)

163164import Streamly.Internal.Data.Stream.IsStream.Common

164− ( fold, fold_, drop, findIndices, reverse, splitOnSeq, take

165+ ( fold, fold_, foldOn, drop, findIndices, reverse, splitOnSeq, take

165166 , takeWhile, mkParallel)

166167import Streamly.Internal.Data.Stream.IsStream.Type

167168 (IsStream, toStreamS, fromStreamD, toStreamD)

src/Streamly/Internal/Data/Stream/StreamD/Type.hs+26

@@ -43,6 +43,7 @@ module Streamly.Internal.Data.Stream.StreamD.Type

4343 -- * Running a 'Fold'

4444 , fold

4545 , fold_

46+ , foldOn

4647

4748 -- * Right Folds

4849 , foldrT

@@ -294,6 +295,31 @@ fold_ (Fold fstep begin done) (Stream step state) = do

294295 b <- done fs

295296 return $! (b, Stream (\ _ _ -> return Stop) ())

296297

298+{-# INLINE_NORMAL foldOn #-}

299+foldOn :: Monad m => Fold m a b -> Stream m a -> Fold m a b

300+foldOn (Fold fstep finitial fextract) (Stream sstep state) =

301+ Fold fstep initial fextract

302+

303+ where

304+

305+ initial = do

306+ res <- finitial

307+ case res of

308+ FL.Partial fs -> go SPEC fs state

309+ FL.Done fb -> return $ FL.Done fb

310+

311+ {-# INLINE go #-}

312+ go !_ !fs st = do

313+ r <- sstep defState st

314+ case r of

315+ Yield x s -> do

316+ res <- fstep fs x

317+ case res of

318+ FL.Done b -> return $ FL.Done b

319+ FL.Partial fs1 -> go SPEC fs1 s

320+ Skip s -> go SPEC fs s

321+ Stop -> return $ FL.Partial fs

322+

297323------------------------------------------------------------------------------

298324-- Right Folds

299325------------------------------------------------------------------------------