149d263 · streamly · git.iko.soy

git.iko.soy/streamly

Change the iterateM implementation to use pure seed and add tests for it

commit149d263b352da49abdea4ef157b2d0fc940d7e11 authorAbhiroop Sarkar <asiamgenius@gmail.com> dateSat 24 Mar 2018, 14:58 (9 years ago) parentc7b9463

3 files changed+18−13

compare with master

unifiedsplit

Changelog.md+2−1 src/Streamly/Prelude.hs+7−7 test/Main.hs+9−5

Changelog.md+2−1

@@ -1,4 +1,5 @@

11## Unreleased

2+* Add `iterate`, `iterateM` stream operations

34### Bug Fixes

45* Fix Zip/AsyncZip applicative instances to handle applicative injection of function like `pure f <*> s1 <*> s2`

@@ -7,7 +8,7 @@

89### Enhancements

910* Make `cons` right associative and provide an operator form `.:` for it

10−* Add `iterateM`, `iterate`, `null`, `tail`, `reverse`, `replicateM`, `scan` stream operations

11+* Add `null`, `tail`, `reverse`, `replicateM`, `scan` stream operations

1112* Improve performance of some stream operations (`foldl`, `dropWhile`)

1213

1314### Bug Fixes

src/Streamly/Prelude.hs+7−7

@@ -126,16 +126,16 @@ each = Prelude.foldr cons nil

126126-- | Iterate a pure function from a seed value, streaming the results forever

127127iterate :: Streaming t => (a -> a) -> a -> t m a

128128iterate step = fromStream . go

129− where

130− go s = scons s (Just (go (step s)))

129+ where

130+ go s = scons s (Just (go (step s)))

131131

132132-- | Iterate a monadic function from a seed value, streaming the results forever

133−iterateM :: (Streaming t, Monad m) => (a -> m a) -> m a -> t m a

133+iterateM :: (Streaming t, Monad m) => (a -> m a) -> a -> t m a

134134iterateM step = fromStream . go

135− where

136− go ms = Stream $ \_ _ yld -> do

137− s <- ms

138− yld s (Just (go (step s)))

135+ where

136+ go s = Stream $ \_ _ yld -> do

137+ a <- step s

138+ yld s (Just (go a))

139139

140140-- | Read lines from an IO Handle into a stream of Strings.

141141fromHandle :: (Streaming t, MonadIO m) => IO.Handle -> t m String

test/Main.hs+9−5

@@ -651,11 +651,15 @@ streamOperations (stream, list, len) = do

651651 return $ str == lst

652652 `shouldReturn` True

653653

654− it "iterate" $ do

655− let lst = take len $ iterate (+ 1) 0

656− str <- A.toList . serially . (A.take len) $ (A.iterate (+ 1) (0 :: Int))

657− return $ str == lst

658− `shouldReturn` True

654+ it "iterate" $

655+ (A.toList . serially . (A.take len) $ (A.iterate (+ 1) (0 :: Int)))

656+ `shouldReturn` (take len $ iterate (+ 1) 0)

657+

658+ it "iterateM" $ do

659+ let addM = (\ y -> return (y + 1))

660+ A.toList . serially . (A.take len) $ A.iterateM addM (0 :: Int)

661+ `shouldReturn` (take len $ iterate (+ 1) 0)

662+

659663

660664 -- Filtering

661665 it "filter all out" $ transform (A.filter (> len)) (filter (> len))