f0c11b5 · streamly · git.iko.soy

git.iko.soy/streamly

on master help sign in

implement foldr/build fusion for unfoldr/foldrM

f0c11b5Harendra Kumar7 years ago

src/Streamly/Streams/StreamK.hs+6−6

compare with master

unifiedsplit

@@ -215,12 +215,12 @@ uncons m =

215

216{-# INLINE unfoldr #-}

217unfoldr :: IsStream t => (b -> Maybe (a, b)) -> b -> t m a

218−unfoldr step = go

218+unfoldr next s0 = build $ \yld stp ->

219− where

219+ let go s =

220− go s = buildS $ \yld stp ->

221− case step s of

220+ case next s of

222− Just (a, b) -> yld a (go b)

221+ Just (a, b) -> yld a (go b)

223− Nothing -> stp

222+ Nothing -> stp

223+ in go s0

224

225{-# INLINE unfoldrM #-}

226unfoldrM :: (IsStream t, MonadAsync m) => (b -> m (Maybe (a, b))) -> b -> t m a

src/Streamly/Streams/StreamK/Type.hs+25

@@ -50,6 +50,7 @@ module Streamly.Streams.StreamK.Type

50 , foldrM

51 , foldrS

52 , foldrSM

53+ , build

53 , buildS

54 , buildS

54 , buildM

55 , buildM

55 , buildSM

56 , buildSM

@@ -550,6 +551,30 @@ foldrSMShared = foldrSMWith foldStreamShared

550-- build

551-- build

551-------------------------------------------------------------------------------

552-------------------------------------------------------------------------------

552

553

554+{-# INLINE_NORMAL build #-}

555+build :: IsStream t => forall a. (forall b. (a -> b -> b) -> b -> b) -> t m a

556+build g = g cons nil

557+

558+{-# RULES "foldrM/build"

559+ forall k z (g :: forall b. (a -> b -> b) -> b -> b).

560+ foldrM k z (build g) = g k z #-}

561+

562+{-# RULES "foldrS/build"

563+ forall k z (g :: forall b. (a -> b -> b) -> b -> b).

564+ foldrS k z (build g) = g k z #-}

565+

566+{-# RULES "foldrS/cons/build"

567+ forall k z x (g :: forall b. (a -> b -> b) -> b -> b).

568+ foldrS k z (x `cons` build g) = k x (g k z) #-}

569+

570+{-# RULES "foldrSShared/build"

571+ forall k z (g :: forall b. (a -> b -> b) -> b -> b).

572+ foldrSShared k z (build g) = g k z #-}

573+

574+{-# RULES "foldrSShared/cons/build"

575+ forall k z x (g :: forall b. (a -> b -> b) -> b -> b).

576+ foldrSShared k z (x `cons` build g) = k x (g k z) #-}

577+

553-- build a stream by applying cons and nil to a build function

578-- build a stream by applying cons and nil to a build function

554{-# INLINE_NORMAL buildS #-}

579{-# INLINE_NORMAL buildS #-}

555buildS :: IsStream t => ((a -> t m a -> t m a) -> t m a -> t m a) -> t m a

580buildS :: IsStream t => ((a -> t m a -> t m a) -> t m a -> t m a) -> t m a