5e38a57 · streamly · git.iko.soy

878-- Merging

879------------------------------------------------------------------------------

880

881−data MergeWithState l r o

882− = MergeBoth l r

883− | MergeWithLeft l r o

884− | MergeWithRight l r o

885− | MergeNoMore (Either l r)

886−

887{-# INLINE_NORMAL mergeBy #-}

881{-# INLINE_NORMAL mergeBy #-}

888mergeBy :: (Monad m) => (a -> a -> Ordering) -> Stream m a -> Stream m a -> Stream m a

882mergeBy :: (Monad m) => (a -> a -> Ordering) -> Stream m a -> Stream m a -> Stream m a

889mergeBy f (Stream stepa ta) (Stream stepb tb) =

883mergeBy f (Stream stepa ta) (Stream stepb tb) =

890− Stream step (MergeBoth ta tb)

884+ Stream step (Just ta, Just tb, Nothing, Nothing)

885+ where

891 {-# INLINE_LATE step #-}

886 {-# INLINE_LATE step #-}

887+

888+ -- one of the values is missing, and the corresponding stream is running

892− step gst (MergeBoth sa sb) = do

889+ step gst (Just sa, sb, Nothing, b) = do

893− ra <- stepa (rstState gst) sa

890+ r <- stepa (rstState gst) sa

894− rb <- stepb (rstState gst) sb

895− case (ra, rb) of

891+ return $ case r of

896− (Yield xa sa', Yield xb sb') -> do

892+ Yield a sa' -> Skip (Just sa', sb, Just a, b)

897− case f xa xb of

893+ Skip sa' -> Skip (Just sa', sb, Nothing, b)

898− LT ->

894+ Stop -> Skip (Nothing, sb, Nothing, b)

899− return $ Yield xa (MergeWithRight sa' sb' xb)

895+

900− _ ->

896+ step gst (sa, Just sb, a, Nothing) = do

901− return $ Yield xb (MergeWithLeft sa' sb' xa)

897+ r <- stepb (rstState gst) sb

902− (Yield xa sa', Stop) -> return $ Yield xa (MergeNoMore (Left sa'))

898+ return $ case r of

903− (Stop, Yield xb sb') -> return $ Yield xb (MergeNoMore (Right sb'))

899+ Yield b sb' -> Skip (sa, Just sb', a, Just b)

904− (Yield xa sa', Skip sb') -> return $ Skip (MergeWithLeft sa' sb' xa)

900+ Skip sb' -> Skip (sa, Just sb', a, Nothing)

905− (Skip sa', Yield xb sb') -> return $ Skip (MergeWithRight sa' sb' xb)

901+ Stop -> Skip (sa, Nothing, a, Nothing)

906− (Skip sa', Skip sb') -> return $ Skip (MergeBoth sa' sb')

902+

907− (Skip sa', Stop) -> return $ Skip (MergeNoMore (Left sa'))

903+ -- both the values are available

908− (Stop, Skip sb') -> return $ Skip (MergeNoMore (Right sb'))

904+ step _ (sa, sb, Just a, Just b) =

909− (Stop, Stop) -> return Stop

905+ return $ case f a b of

910− step gst (MergeWithLeft sa sb x) = do

906+ LT -> Yield a (sa, sb, Nothing, Just b)

911− rb <- stepb (rstState gst) sb

907+ _ -> Yield b (sa, sb, Just a, Nothing)

912− case rb of

908+

913− Yield xb sb' -> do

909+ -- one of the values is missing, corresponding stream is done

914− case f x xb of

910+ step _ (Nothing, sb, Nothing, Just b) = do

915− LT -> return $ Yield x (MergeWithRight sa sb' xb)

911+ return $ Yield b (Nothing, sb, Nothing, Nothing)

916− _ -> return $ Yield xb (MergeWithLeft sa sb' x)

912+

917− Skip sb' -> return $ Skip (MergeWithLeft sa sb' x)

913+ step _ (sa, Nothing, Just a, Nothing) = do

918− Stop -> return $ Yield x (MergeNoMore (Left sa))

914+ return $ Yield a (sa, Nothing, Nothing, Nothing)

919− step gst (MergeWithRight sa sb x) = do

915+

920− ra <- stepa (rstState gst) sa

916+ step _ (Nothing, Nothing, Nothing, Nothing) = return Stop

921− case ra of

922− Yield xa sa' -> do

923− case f xa x of

924− LT -> return $ Yield xa (MergeWithRight sa' sb x)

925− _ -> return $ Yield x (MergeWithLeft sa' sb xa)

926− Skip sa' -> return $ Skip (MergeWithRight sa' sb x)

927− Stop -> return $ Yield x (MergeNoMore (Right sb))

928− step gst (MergeNoMore (Left sa)) = do

929− ra <- stepa (rstState gst) sa

930− case ra of

931− Yield xa sa' -> return $ Yield xa (MergeNoMore (Left sa'))

932− Skip sa' -> return $ Skip (MergeNoMore (Left sa'))

933− Stop -> return Stop

934− step gst (MergeNoMore (Right sb)) = do

935− rb <- stepb (rstState gst) sb

936− case rb of

937− Yield xb sb' -> return $ Yield xb (MergeNoMore (Right sb'))

938− Skip sb' -> return $ Skip (MergeNoMore (Right sb'))

939− Stop -> return Stop

940

917

941------------------------------------------------------------------------------

918------------------------------------------------------------------------------

942-- Transformation comprehensions

919-- Transformation comprehensions