977c344 · streamly · git.iko.soy

git.iko.soy/streamly

Add Foldable and Traversable instances for StreamD and StreamK

commit977c344600cb7ef1555ef8c4f4d0279e21ca51f0 authorAbhiroop Sarkar <asiamgenius@gmail.com> dateFri 2 Nov 2018, 14:08 (8 years ago) parentc7666a7

2 files changed+31

compare with master

unifiedsplit

src/Streamly/Streams/StreamD.hs+16 src/Streamly/Streams/StreamK.hs+15

src/Streamly/Streams/StreamD.hs+16

@@ -127,6 +127,8 @@ import Prelude

127127 notElem, null, head, tail, zipWith)

128128

129129import Streamly.SVar (MonadAsync, State(..), defState, rstState)

130+

131+import qualified Data.Foldable as F

130132import qualified Streamly.Streams.StreamK as K

131133

132134------------------------------------------------------------------------------

@@ -148,6 +150,20 @@ instance Functor (Step s) where

148150-- current state, and the current state.

149151data Stream m a = forall s. Stream (State K.Stream m a -> s -> m (Step s a)) s

150152

153+instance (Foldable m, Monad m) => Foldable (Stream m) where

154+ {-# INLINE foldMap #-}

155+ foldMap f = F.fold . toFoldable . map f

156+ where

157+ toFoldable :: (Monad m, Monoid a) => Stream m a -> m a

158+ toFoldable = foldr mappend mempty

159+

160+instance (Traversable m, Monad m) => Traversable (Stream m) where

161+ {-# INLINE traverse #-}

162+ traverse f = sequenceA . fmap f

163+

164+ {-# INLINE sequenceA #-}

165+ sequenceA = traverse id

166+

151167------------------------------------------------------------------------------

152168-- Construction

153169------------------------------------------------------------------------------

src/Streamly/Streams/StreamK.hs+15

@@ -153,6 +153,7 @@ import Prelude

153153 take, filter, all, any, takeWhile, drop, dropWhile, minimum,

154154 maximum, elem, notElem, null, head, tail, init, zipWith, lookup,

155155 foldr1)

156+import qualified Data.Foldable as F

156157import qualified Prelude

157158

158159import Streamly.SVar

@@ -188,6 +189,20 @@ newtype Stream m a =

188189 -> m r

189190 }

190191

192+instance (Foldable m, Monad m) => Foldable (Stream m) where

193+ {-# INLINE foldMap #-}

194+ foldMap f = F.fold . toFoldable . map f

195+ where

196+ toFoldable :: (Monad m, Monoid a) => Stream m a -> m a

197+ toFoldable = foldr mappend mempty

198+

199+instance (Traversable m, Monad m) => Traversable (Stream m) where

200+ {-# INLINE traverse #-}

201+ traverse f = sequenceA . fmap f

202+

203+ {-# INLINE sequenceA #-}

204+ sequenceA = traverse id

205+

191206-- XXX make this the default "unStream"

192207-- | unwraps the Stream type producing the stream function that can be run with

193208-- continuations.