dea4c4e · streamly · git.iko.soy

git.iko.soy/streamly

Fix takeEQ

takeEQ was not terminating promptly, it was holding up the output till the next input even though it could have terminated earlier.

commitdea4c4eedbf1f97e93b8ef07339d8a12fc563261 authorHarendra Kumar <harendra@composewell.com> dateSun 6 Dec 2020, 19:56 (6 years ago) parent425adca

2 files changed+25−11

compare with master

unifiedsplit

src/Streamly/Internal/Data/Parser.hs+3−2 src/Streamly/Internal/Data/Parser/ParserD.hs+22−9

src/Streamly/Internal/Data/Parser.hs+3−2

@@ -408,8 +408,9 @@ take n = K.toParserK . D.take n

408408

409409-- | Stops after taking exactly @n@ input elements.

410410--

411−-- * Stops - after @n@ elements.

412−-- * Fails - if the stream ends before it can collect @n@ elements.

411+-- * Stops - after consuming @n@ elements.

412+-- * Fails - if the stream or the collecting fold ends before it can collect

413+-- exactly @n@ elements.

413414--

414415-- >>> S.parse (PR.takeEQ 4 FL.toList) $ S.fromList [1,0,1]

415416-- > "takeEQ: Expecting exactly 4 elements, got 3"

src/Streamly/Internal/Data/Parser/ParserD.hs+22−9

@@ -310,7 +310,6 @@ either parser = Parser step initial extract

310310take :: Monad m => Int -> Fold m a b -> Parser m a b

311311take n fld = fromFold $ FL.ltake n fld

312312

313−-- XXX We are purposefully ignoring the input here

314313-- | See 'Streamly.Internal.Data.Parser.takeEQ'.

315314--

316315-- /Internal/

@@ -326,21 +325,35 @@ takeEQ cnt (Fold fstep finitial fextract) = Parser step initial extract

326325 initial = Tuple' 0 <$> finitial

327326

328327 step (Tuple' i r) a

329− | i < n = do

328+ | i1 < n = do

330329 res <- fstep r a

331330 return

332331 $ case res of

333− FL.Partial s -> Continue 0 $ Tuple' (i + 1) s

334− FL.Done _ -> Error $ err (i + 1)

332+ FL.Partial s -> Continue 0 $ Tuple' i1 s

333+ FL.Done _ ->

334+ Error

335+ $ "takeEQ: the collecting fold terminated after "

336+ ++ "consuming" ++ show i1 ++ " elements"

337+ | i1 == n = do

338+ res <- fstep r a

339+ Done 0

340+ <$> case res of

341+ FL.Partial s -> fextract s

342+ FL.Done b -> return b

343+ -- reachable only when n == 0

335344 | otherwise = Done 1 <$> fextract r

336345

337− extract (Tuple' i r)

338− | i == n = fextract r

339− | otherwise = throwM $ ParseError $ err i

346+ where

340347

341− err i =

342− "takeEQ: Expecting exactly " ++ show n ++ " elements, got " ++ show i

348+ i1 = i + 1

343349

350+ extract (Tuple' i r)

351+ | i == 0 && n == 0 = fextract r

352+ | otherwise =

353+ throwM

354+ $ ParseError

355+ $ "takeEQ: Expecting exactly "

356+ ++ show n ++ " elements, got " ++ show i

344357

345358-- | See 'Streamly.Internal.Data.Parser.takeGE'.

346359--