e6c75f6 · streamly · git.iko.soy

git.iko.soy/streamly

Add Prelude#init

commite6c75f6aa92db1dc003ddadf94aa2d8dbc204015 authorVeladus <veladus@web.de> dateMon 23 Jul 2018, 16:51 (8 years ago) parent2af3833

3 files changed+28−2

compare with master

unifiedsplit

src/Streamly/Prelude.hs+7−1 src/Streamly/Streams/StreamK.hs+16−1 test/Prop.hs+5

src/Streamly/Prelude.hs+7−1

@@ -93,6 +93,7 @@ module Streamly.Prelude

9393 , head

9494 , tail

9595 , last

96+ , init

9697 , elem

9798 , notElem

9899 , length

@@ -160,7 +161,7 @@ import Prelude

160161 hiding (filter, drop, dropWhile, take, takeWhile, zipWith, foldr,

161162 foldl, map, mapM, mapM_, sequence, all, any, sum, product, elem,

162163 notElem, maximum, minimum, head, last, tail, length, null,

163− reverse, iterate)

164+ reverse, iterate, init)

164165import qualified Prelude

165166import qualified System.IO as IO

166167

@@ -517,6 +518,11 @@ head m = K.head m

517518tail :: (IsStream t, Monad m) => SerialT m a -> m (Maybe (t m a))

518519tail m = K.tail (K.adapt m)

519520

521+-- | Extract all but the last element of the stream, if any.

522+{-# INLINE init #-}

523+init :: (IsStream t, Monad m) => SerialT m a -> m (Maybe (t m a))

524+init m = K.init (K.adapt m)

525+

520526-- | Extract the last element of the stream, if any.

521527--

522528-- @since 0.1.1

src/Streamly/Streams/StreamK.hs+16−1

@@ -81,6 +81,7 @@ module Streamly.Streams.StreamK

8181 , null

8282 , head

8383 , tail

84+ , init

8485 , elem

8586 , notElem

8687 , all

@@ -141,7 +142,7 @@ import Data.Semigroup (Semigroup(..))

141142import Prelude

142143 hiding (foldl, foldr, last, map, mapM, mapM_, repeat, sequence,

143144 take, filter, all, any, takeWhile, drop, dropWhile, minimum,

144− maximum, elem, notElem, null, head, tail, zipWith)

145+ maximum, elem, notElem, null, head, tail, init, zipWith)

145146import qualified Prelude

146147

147148import Streamly.SVar

@@ -570,6 +571,20 @@ tail m =

570571 yieldk _ r = return $ Just $ fromStream r

571572 in unStream (toStream m) defState stop single yieldk

572573

574+{-# INLINE init #-}

575+init :: (IsStream t, Monad m) => t m a -> m (Maybe (t m a))

576+init m = go1 (toStream m)

577+ where

578+ go1 m1 = do

579+ r <- uncons m1

580+ case r of

581+ Nothing -> return Nothing

582+ Just (h, t) -> return . Just . fromStream $ go h t

583+ go p m1 = Stream $ \_ stp sng yld ->

584+ let single _ = sng p

585+ yieldk a x = yld p $ go a x

586+ in unStream m1 defState stp single yieldk

587+

573588{-# INLINE elem #-}

574589elem :: (IsStream t, Monad m, Eq a) => a -> t m a -> m Bool

575590elem e m = go (toStream m)

test/Prop.hs+5

@@ -496,6 +496,11 @@ serialEliminationOps constr desc t = do

496496 Nothing -> return Nothing

497497 Just s -> S.toList s >>= return . Just

498498 prop (desc ++ " last") $ eliminateOp constr (wrapMaybe last) $ S.last . t

499+ prop (desc ++ " init") $ eliminateOp constr (wrapMaybe init) $ \x -> do

500+ r <- S.init (t x)

501+ case r of

502+ Nothing -> return Nothing

503+ Just s -> S.toList s >>= return . Just

499504

500505transformOpsWord8

501506 :: ([Word8] -> t IO Word8)