3d12532 · streamly · git.iko.soy

git.iko.soy/streamly

Add the pure iterate function

commit3d125328a83825d5272ca70b8c8c6f42eeb7226d authorAbhiroop Sarkar <asiamgenius@gmail.com> dateThu 22 Mar 2018, 21:47 (9 years ago) parent68b6736

3 files changed+15−2

compare with master

unifiedsplit

Changelog.md+1−1 src/Streamly/Prelude.hs+8−1 test/Main.hs+6

Changelog.md+1−1

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

88### Enhancements

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

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

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

1111* Improve performance of some stream operations (`foldl`, `dropWhile`)

1212

1313### Bug Fixes

src/Streamly/Prelude.hs+8−1

@@ -24,6 +24,7 @@ module Streamly.Prelude

2424 , unfoldr

2525 , unfoldrM

2626 , each

27+ , iterate

2728

2829 -- * Elimination

2930 -- ** General Folds

@@ -85,7 +86,8 @@ import Prelude hiding (filter, drop, dropWhile, take,

8586 mapM, mapM_, sequence, all, any,

8687 sum, product, elem, notElem,

8788 maximum, minimum, head, last,

88− tail, length, null, reverse)

89+ tail, length, null, reverse,

90+ iterate)

8991import qualified Prelude

9092import qualified System.IO as IO

9193

@@ -120,6 +122,11 @@ unfoldrM step = fromStream . go

120122each :: (Streaming t, Foldable f) => f a -> t m a

121123each = Prelude.foldr cons nil

122124

125+iterate :: Streaming t => (a -> a) -> a -> t m a

126+iterate f = fromStream . go

127+ where

128+ go s = scons s (Just (go (f s)))

129+

123130-- | Read lines from an IO Handle into a stream of Strings.

124131fromHandle :: (Streaming t, MonadIO m) => IO.Handle -> t m String

125132fromHandle h = fromStream go

test/Main.hs+6

@@ -651,6 +651,12 @@ 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

659+

654660 -- Filtering

655661 it "filter all out" $ transform (A.filter (> len)) (filter (> len))

656662 it "filter all in" $ transform (A.filter (<= len)) (filter (<= len))