{-# LANGUAGE FlexibleContexts, BangPatterns, TupleSections #-} -- |Monadic Iteratees: -- incremental input parsers, processors and transformers -- -- This module provides many basic iteratees from which more complicated -- iteratees can be built. In general these iteratees parallel those in -- @Data.List@, with some additions. module Data.Iteratee.ListLike ( -- * Iteratees -- ** Iteratee Utilities isFinished ,stream2list ,stream2stream -- ** Basic Iteratees ,break ,dropWhile ,drop ,head ,tryHead ,last ,heads ,peek ,roll ,length ,chunkLength ,takeFromChunk -- ** Nested iteratee combinators ,breakE ,take ,takeUpTo ,takeWhile ,takeWhileE ,mapStream ,rigidMapStream ,filter ,group ,groupBy ,merge ,mergeByChunks -- ** Folds ,foldl ,foldl' ,foldl1 ,foldl1' -- ** Special Folds ,sum ,product -- * Enumerators -- ** Basic enumerators ,enumPureNChunk -- ** Enumerator Combinators ,enumPair ,enumWith ,zip ,zip3 ,zip4 ,zip5 ,sequence_ -- ** Monadic functions ,mapM_ ,foldM -- * Re-exported modules ,module Data.Iteratee.Iteratee ) where import Prelude hiding (mapM_, null, head, last, drop, dropWhile, take, takeWhile, break, foldl, foldl1, length, filter, sum, product, zip, zip3, sequence_) import qualified Prelude as Prelude import qualified Data.ListLike as LL import qualified Data.ListLike.FoldableLL as FLL import Data.Iteratee.Iteratee import Data.Monoid import Data.Maybe (catMaybes) import Control.Applicative ((<$>), (<*>), (<*)) import Control.Monad (liftM, liftM2, mplus, (<=<)) import Control.Monad.Trans.Class import Data.Word (Word8) import qualified Data.ByteString as B import qualified Data.ByteString.Char8 as BC -- Useful combinators for implementing iteratees and enumerators -- | Check if a stream has received 'EOF'. isFinished :: (Monad m, Nullable s) => Iteratee s m Bool isFinished = liftI check where check c@(Chunk xs) | nullC xs = liftI check | otherwise = idone False c check s@(EOF _) = idone True s {-# INLINE isFinished #-} -- ------------------------------------------------------------------------ -- Primitive iteratees -- |Read a stream to the end and return all of its elements as a list. -- This iteratee returns all data from the stream *strictly*. stream2list :: (Monad m, Nullable s, LL.ListLike s el) => Iteratee s m [el] stream2list = liftM (concatMap LL.toList) getChunks {-# INLINE stream2list #-} -- |Read a stream to the end and return all of its elements as a stream. -- This iteratee returns all data from the stream *strictly*. stream2stream :: (Monad m, Nullable s, Monoid s) => Iteratee s m s stream2stream = liftM mconcat getChunks {-# INLINE stream2stream #-} -- ------------------------------------------------------------------------ -- Parser combinators -- |Takes an element predicate and returns the (possibly empty) prefix of -- the stream. None of the characters in the string satisfy the character -- predicate. -- If the stream is not terminated, the first character of the remaining stream -- satisfies the predicate. -- -- N.B. 'breakE' should be used in preference to @break@. -- @break@ will retain all data until the predicate is met, which may -- result in a space leak. -- -- The analogue of @List.break@ break :: (Monad m, LL.ListLike s el) => (el -> Bool) -> Iteratee s m s break cpred = icont (step mempty) Nothing where step bfr (Chunk str) | LL.null str = icont (step bfr) Nothing | otherwise = case LL.break cpred str of (str', tail') | LL.null tail' -> icont (step (bfr `mappend` str)) Nothing | otherwise -> idone (bfr `mappend` str') (Chunk tail') step bfr stream = idone bfr stream {-# INLINE break #-} -- |Attempt to read the next element of the stream and return it -- Raise a (recoverable) error if the stream is terminated. -- -- The analogue of @List.head@ -- -- Because @head@ can raise an error, it shouldn't be used when constructing -- iteratees for @convStream@. Use @tryHead@ instead. head :: (Monad m, LL.ListLike s el) => Iteratee s m el head = liftI step where step (Chunk vec) | LL.null vec = icont step Nothing | otherwise = idone (LL.head vec) (Chunk $ LL.tail vec) step stream = icont step (Just (setEOF stream)) {-# INLINE head #-} -- | Similar to @head@, except it returns @Nothing@ if the stream -- is terminated. tryHead :: (Monad m, LL.ListLike s el) => Iteratee s m (Maybe el) tryHead = liftI step where step (Chunk vec) | LL.null vec = liftI step | otherwise = idone (Just $ LL.head vec) (Chunk $ LL.tail vec) step stream = idone Nothing stream {-# INLINE tryHead #-} -- |Attempt to read the last element of the stream and return it -- Raise a (recoverable) error if the stream is terminated -- -- The analogue of @List.last@ last :: (Monad m, LL.ListLike s el, Nullable s) => Iteratee s m el last = liftI (step Nothing) where step l (Chunk xs) | nullC xs = liftI (step l) | otherwise = liftI $ step (Just $ LL.last xs) step l s@(EOF _) = case l of Nothing -> icont (step l) . Just . setEOF $ s Just x -> idone x s {-# INLINE last #-} -- |Given a sequence of characters, attempt to match them against -- the characters on the stream. Return the count of how many -- characters matched. The matched characters are removed from the -- stream. -- For example, if the stream contains 'abd', then (heads 'abc') -- will remove the characters 'ab' and return 2. heads :: (Monad m, Nullable s, LL.ListLike s el, Eq el) => s -> Iteratee s m Int heads st | nullC st = return 0 heads st = loop 0 st where loop cnt xs | nullC xs = return cnt | otherwise = liftI (step cnt xs) step cnt str (Chunk xs) | nullC xs = liftI (step cnt str) step cnt str stream | nullC str = idone cnt stream step cnt str s@(Chunk xs) = if LL.head str == LL.head xs then step (succ cnt) (LL.tail str) (Chunk $ LL.tail xs) else idone cnt s step cnt _ stream = idone cnt stream {-# INLINE heads #-} -- |Look ahead at the next element of the stream, without removing -- it from the stream. -- Return @Just c@ if successful, return @Nothing@ if the stream is -- terminated by 'EOF'. peek :: (Monad m, LL.ListLike s el) => Iteratee s m (Maybe el) peek = liftI step where step s@(Chunk vec) | LL.null vec = liftI step | otherwise = idone (Just $ LL.head vec) s step stream = idone Nothing stream {-# INLINE peek #-} -- | Return a chunk of @t@ elements length while consuming @d@ elements -- from the stream. Useful for creating a 'rolling average' with -- 'convStream'. roll :: (Monad m, Functor m, Nullable s, LL.ListLike s el, LL.ListLike s' s) => Int -- ^ length of chunk (t) -> Int -- ^ amount to consume (d) -> Iteratee s m s' roll t d | t > d = liftI step where step (Chunk vec) | LL.length vec >= d = idone (LL.singleton $ LL.take t vec) (Chunk $ LL.drop d vec) | LL.length vec >= t = idone (LL.singleton $ LL.take t vec) mempty <* drop (d-LL.length vec) | LL.null vec = liftI step | otherwise = liftI (step' vec) step stream = idone LL.empty stream step' v1 (Chunk vec) = step . Chunk $ v1 `mappend` vec step' v1 stream = idone (LL.singleton v1) stream roll t d = LL.singleton <$> joinI (take t stream2stream) <* drop (d-t) -- d is >= t, so this version works {-# INLINE roll #-} -- |Drop n elements of the stream, if there are that many. -- -- The analogue of @List.drop@ drop :: (Monad m, Nullable s, LL.ListLike s el) => Int -> Iteratee s m () drop 0 = return () drop n' = liftI (step n') where step n (Chunk str) | LL.length str < n = liftI (step (n - LL.length str)) | otherwise = idone () (Chunk (LL.drop n str)) step _ stream = idone () stream {-# INLINE drop #-} -- |Skip all elements while the predicate is true. -- -- The analogue of @List.dropWhile@ dropWhile :: (Monad m, LL.ListLike s el) => (el -> Bool) -> Iteratee s m () dropWhile p = liftI step where step (Chunk str) | LL.null left = liftI step | otherwise = idone () (Chunk left) where left = LL.dropWhile p str step stream = idone () stream {-# INLINE dropWhile #-} -- | Return the total length of the remaining part of the stream. -- -- This forces evaluation of the entire stream. -- -- The analogue of @List.length@ length :: (Monad m, Num a, LL.ListLike s el) => Iteratee s m a length = liftI (step 0) where step !i (Chunk xs) = liftI (step $ i + fromIntegral (LL.length xs)) step !i stream = idone i stream {-# INLINE length #-} -- | Get the length of the current chunk, or @Nothing@ if 'EOF'. -- -- This function consumes no input. chunkLength :: (Monad m, LL.ListLike s el) => Iteratee s m (Maybe Int) chunkLength = liftI step where step s@(Chunk xs) = idone (Just $ LL.length xs) s step stream = idone Nothing stream {-# INLINE chunkLength #-} -- | Take @n@ elements from the current chunk, or the whole chunk if -- @n@ is greater. takeFromChunk :: (Monad m, Nullable s, LL.ListLike s el) => Int -> Iteratee s m s takeFromChunk n | n <= 0 = return empty takeFromChunk n = liftI step where step (Chunk xs) = let (h,t) = LL.splitAt n xs in idone h $ Chunk t step stream = idone empty stream {-# INLINE takeFromChunk #-} -- --------------------------------------------------- -- The converters show a different way of composing two iteratees: -- `vertical' rather than `horizontal' -- |Takes an element predicate and an iteratee, running the iteratee -- on all elements of the stream until the predicate is met. -- -- the following rule relates @break@ to @breakE@ -- @break@ pred === @joinI@ (@breakE@ pred stream2stream) -- -- @breakE@ should be used in preference to @break@ whenever possible. breakE :: (Monad m, LL.ListLike s el, NullPoint s) => (el -> Bool) -> Enumeratee s s m a breakE cpred = eneeCheckIfDonePass (icont . step) where step k (Chunk s) | LL.null s = liftI (step k) | otherwise = case LL.break cpred s of (str', tail') | LL.null tail' -> eneeCheckIfDonePass (icont . step) . k $ Chunk str' | otherwise -> idone (k $ Chunk str') (Chunk tail') step k stream = idone (k stream) stream {-# INLINE breakE #-} -- |Read n elements from a stream and apply the given iteratee to the -- stream of the read elements. Unless the stream is terminated early, we -- read exactly n elements, even if the iteratee has accepted fewer. -- -- The analogue of @List.take@ take :: (Monad m, Nullable s, LL.ListLike s el) => Int -- ^ number of elements to consume -> Enumeratee s s m a take n' iter | n' <= 0 = return iter | otherwise = Iteratee $ \od oc -> runIter iter (on_done od oc) (on_cont od oc) where on_done od oc x _ = runIter (drop n' >> return (return x)) od oc on_cont od oc k Nothing = if n' == 0 then od (liftI k) (Chunk mempty) else runIter (liftI (step n' k)) od oc on_cont od oc _ (Just e) = runIter (drop n' >> throwErr e) od oc step n k (Chunk str) | LL.null str = liftI (step n k) | LL.length str <= n = take (n - LL.length str) $ k (Chunk str) | otherwise = idone (k (Chunk s1)) (Chunk s2) where (s1, s2) = LL.splitAt n str step _n k stream = idone (k stream) stream {-# SPECIALIZE take :: Monad m => Int -> Enumeratee [el] [el] m a #-} {-# SPECIALIZE take :: Monad m => Int -> Enumeratee B.ByteString B.ByteString m a #-} {-# SPECIALIZE take :: Monad m => Int -> Enumeratee BC.ByteString BC.ByteString m a #-} -- |Read n elements from a stream and apply the given iteratee to the -- stream of the read elements. If the given iteratee accepted fewer -- elements, we stop. -- This is the variation of 'take' with the early termination -- of processing of the outer stream once the processing of the inner stream -- finished early. -- -- Iteratees composed with 'takeUpTo' will consume only enough elements to -- reach a done state. Any remaining data will be available in the outer -- stream. -- -- > > let iter = do -- > h <- joinI $ takeUpTo 5 I.head -- > t <- stream2list -- > return (h,t) -- > -- > > enumPureNChunk [1..10::Int] 3 iter >>= run >>= print -- > (1,[2,3,4,5,6,7,8,9,10]) -- > -- > > enumPureNChunk [1..10::Int] 7 iter >>= run >>= print -- > (1,[2,3,4,5,6,7,8,9,10]) -- -- in each case, @I.head@ consumes only one element, returning the remaining -- 4 elements to the outer stream takeUpTo :: (Monad m, Nullable s, LL.ListLike s el) => Int -> Enumeratee s s m a takeUpTo i iter | i <= 0 = return iter | otherwise = Iteratee $ \od oc -> runIter iter (onDone od oc) (onCont od oc) where onDone od oc x str = runIter (idone (return x) str) od oc onCont od oc k Nothing = if i == 0 then od (liftI k) (Chunk mempty) else runIter (liftI (step i k)) od oc onCont od oc _ (Just e) = runIter (throwErr e) od oc step n k (Chunk str) | LL.null str = liftI (step n k) | LL.length str < n = takeUpTo (n - LL.length str) $ k (Chunk str) | otherwise = -- check to see if the inner iteratee has completed, and if so, -- grab any remaining stream to put it in the outer iteratee. -- the outer iteratee is always complete at this stage, although -- the inner may not be. let (s1, s2) = LL.splitAt n str in Iteratee $ \od' _ -> do res <- runIter (k (Chunk s1)) (\a s -> return $ Left (a, s)) (\k' e -> return $ Right (k',e)) case res of Left (a,Chunk s1') -> od' (return a) (Chunk $ s1' `LL.append` s2) Left (a,s') -> od' (idone a s') (Chunk s2) Right (k',e) -> od' (icont k' e) (Chunk s2) step _ k stream = idone (k stream) stream {-# SPECIALIZE takeUpTo :: Monad m => Int -> Enumeratee [el] [el] m a #-} {-# SPECIALIZE takeUpTo :: Monad m => Int -> Enumeratee B.ByteString B.ByteString m a #-} {-# INLINABLE takeUpTo #-} -- | Takes an element predicate and returns the (possibly empty) -- prefix of the stream. All characters -- in the string will satisfy the character predicate. If the stream -- is not terminated, the first character of the -- remaining stream will not satisfy the predicate. -- -- The analogue of @List.takeWhile@, see also @break@ and @takeWhileE@ takeWhile :: (LL.ListLike s el, Monad m) => (el -> Bool) -> Iteratee s m s takeWhile = break . (not .) {-# INLINEABLE takeWhile #-} -- |Takes an element predicate and an iteratee, running the iteratee -- on all elements of the stream while the predicate is met. -- -- This is preferred to @takeWhile@. takeWhileE :: (Monad m, LL.ListLike s el, NullPoint s) => (el -> Bool) -> Enumeratee s s m a takeWhileE = breakE . (not .) {-# INLINEABLE takeWhileE #-} -- |Map the stream: another iteratee transformer -- Given the stream of elements of the type @el@ and the function @(el->el')@, -- build a nested stream of elements of the type @el'@ and apply the -- given iteratee to it. -- -- The analog of @List.map@ mapStream :: (Monad m ,LL.ListLike (s el) el ,LL.ListLike (s el') el' ,NullPoint (s el) ,LooseMap s el el') => (el -> el') -> Enumeratee (s el) (s el') m a mapStream f = mapChunks (lMap f) {-# SPECIALIZE mapStream :: Monad m => (el -> el') -> Enumeratee [el] [el'] m a #-} -- |Map the stream rigidly. -- -- Like 'mapStream', but the element type cannot change. -- This function is necessary for @ByteString@ and similar types -- that cannot have 'LooseMap' instances, and may be more efficient. rigidMapStream :: (Monad m, LL.ListLike s el, NullPoint s) => (el -> el) -> Enumeratee s s m a rigidMapStream f = mapChunks (LL.rigidMap f) {-# SPECIALIZE rigidMapStream :: Monad m => (el -> el) -> Enumeratee [el] [el] m a #-} {-# SPECIALIZE rigidMapStream :: Monad m => (Word8 -> Word8) -> Enumeratee B.ByteString B.ByteString m a #-} -- |Creates an 'enumeratee' with only elements from the stream that -- satisfy the predicate function. The outer stream is completely consumed. -- -- The analogue of @List.filter@ filter :: (Monad m, Functor m, Nullable s, LL.ListLike s el) => (el -> Bool) -> Enumeratee s s m a filter p = convStream (LL.filter p <$> getChunk) {-# INLINE filter #-} -- |Creates an 'Enumeratee' in which elements from the stream are -- grouped into @sz@-sized blocks. The final block may be smaller -- than \sz\. group :: (LL.ListLike s el, Monad m, Nullable s) => Int -- ^ size of group -> Enumeratee s [s] m a group cksz iinit = liftI (step 0 id iinit) where -- there are two cases to consider for performance purposes: -- 1 - grouping lots of small chunks into bigger chunks -- 2 - breaking large chunks into smaller pieces -- case 2 is easier, simply split a chunk into as many pieces as necessary -- and pass them to the inner iteratee as one list. @gsplit@ does this. -- -- case 1 is a bit harder, need to hold onto each chunk and coalesce them -- after enough have been received. Currently using a difference list -- for this, i.e ([s] -> [s]) -- -- not using eneeCheckIfDone because that loses final chunks at EOF step sz pfxd icur (Chunk s) | LL.null s = liftI (step sz pfxd icur) | LL.length s + sz < cksz = liftI (step (sz+LL.length s) (pfxd . (s:)) icur) | otherwise = let (full, rest) = gsplit . mconcat $ pfxd [s] pfxd' = if LL.null rest then id else (rest:) onDone x str = return $ Left (x,str) onCont k Nothing = return . Right . Left . k $ Chunk full onCont k e = return . Right $ Right (liftI k, e) in do res <- lift $ runIter icur onDone onCont case res of Left (x,str) -> idone (idone x str) (Chunk rest) Right (Left inext) -> liftI $ step (LL.length rest) pfxd' inext Right (Right (inext, e)) -> icont (step (LL.length rest) pfxd' inext) e step _ pfxd icur mErr = case pfxd [] of [] -> idone icur mErr rest -> do inext <- lift $ enumPure1Chunk [mconcat rest] icur idone inext mErr gsplit ls = case LL.splitAt cksz ls of (g, rest) | LL.null rest -> if LL.length g == cksz then ([g], LL.empty) else ([], g) | otherwise -> let (grest, leftover) = gsplit rest g' = g : grest in (g', leftover) -- | Creates an 'enumeratee' in which elements are grouped into -- contiguous blocks that are equal according to a predicate. -- -- The analogue of 'List.groupBy' groupBy :: (LL.ListLike s el, Monad m, Nullable s) => (el -> el -> Bool) -> Enumeratee s [s] m a groupBy same iinit = liftI $ go iinit (const True, id) where -- As in group, need to handle grouping efficiently when we're fed -- many small chunks. -- -- Move the accumulation of groups by chunks into an accumulator -- that runs through gsplit, which is pfx / partial here. When we -- get a chunk, use gsplit to retrieve any full chunks and get the -- carried accumulator. -- -- At the end, "finish" the accumulator and handle the last chunk, -- unless the stream was entirely empty and there is no -- accumulator. go icurr pfx (Chunk s) = case gsplit pfx s of ([], partial) -> liftI $ go icurr partial (full, partial) -> do -- if the inner iteratee is done, the outer iteratee needs to be -- notified to terminate. -- if the inner iteratee is in an error state, that error should -- be lifted to the outer iteratee let onCont k Nothing = return $ Right $ Left $ k $ Chunk full onCont k e = return $ Right $ Right (liftI k, e) onDone x str = return $ Left (x,str) res <- lift $ runIter icurr onDone onCont case res of Left (x,str) -> idone (idone x str) (Chunk (mconcat $ snd partial [])) Right (Left inext) -> liftI $ go inext partial Right (Right (inext,e)) -> icont (go inext partial) e go icurr (_inpfx, pfxd) (EOF mex) = case pfxd [] of [] -> lift . enumChunk (EOF mex) $ icurr rest -> do inext <- lift . enumPure1Chunk [mconcat rest] $ icurr lift . enumChunk (EOF mex) $ inext -- Here, gsplit carries an accumulator consisting of a predicate -- "inpfx" that indicates whether a new element belongs in the -- growing group, and a difference list to ultimately generate the -- group. -- -- The initial accumulator is a group that can accept anything and -- is empty. -- -- New chunks are split into groups. The cases are -- 0. Trivially, empty chunk -- 1. One chunk, in the currently growing group: continue the -- current prefix (and generate a new predicate, in case we had -- the initial predicate -- 2. One chunk, but not in the current group: finish the -- current group and return a new accumulator for the -- newly-started gorup -- 3. Multiple chunks, the first of which completes the -- currently growing group -- 4. Multiple chunks, the first of which is a new group -- separate from the currently-growing group gsplit (inpfx, pfxd) curr = case llGroupBy same curr of [] -> ([], (inpfx, pfxd)) [g0] | inpfx (LL.head g0) -> ([], (same $ LL.head g0, pfxd . (g0 :))) | otherwise -> ([mconcat $ pfxd []], (same $ LL.head g0, pfxd . (g0 :))) (g0:grest@(_:_)) | inpfx (LL.head g0) -> let glast = Prelude.last grest gfirst = mconcat $ (pfxd . (g0 :)) [] gdone = gfirst : Prelude.init grest in ( gdone, (same (LL.head glast), (glast :)) ) | otherwise -> let glast = Prelude.last grest gfirst = mconcat $ pfxd [] gdone = gfirst : Prelude.init grest in ( gdone, (same (LL.head glast), (glast :)) ) llGroupBy eq l -- Copied from Data.ListLike, avoid spurious (Eq el) constraint | LL.null l = [] | otherwise = (LL.cons x ys):(llGroupBy eq zs) where (ys, zs) = LL.span (eq x) xs x = LL.head l xs = LL.tail l {-# INLINE groupBy #-} -- | @merge@ offers another way to nest iteratees: as a monad stack. -- This allows for the possibility of interleaving data from multiple -- streams. -- -- > -- print each element from a stream of lines. -- > logger :: (MonadIO m) => Iteratee [ByteString] m () -- > logger = mapM_ (liftIO . putStrLn . B.unpack) -- > -- > -- combine alternating lines from two sources -- > -- To see how this was derived, follow the types from -- > -- 'ileaveLines logger' and work outwards. -- > run =<< enumFile 10 "file1" (joinI $ enumLinesBS $ -- > ( enumFile 10 "file2" . joinI . enumLinesBS $ joinI -- > (ileaveLines logger)) >>= run) -- > -- > ileaveLines :: (Functor m, Monad m) -- > => Enumeratee [ByteString] [ByteString] (Iteratee [ByteString] m) -- > [ByteString] -- > ileaveLines = merge (\l1 l2 -> -- > [B.pack "f1:\n\t" ,l1 ,B.pack "f2:\n\t" ,l2 ] -- > -- > -- merge :: (LL.ListLike s1 el1 ,LL.ListLike s2 el2 ,Nullable s1 ,Nullable s2 ,Monad m ,Functor m) => (el1 -> el2 -> b) -> Enumeratee s2 b (Iteratee s1 m) a merge f = convStream $ f <$> lift head <*> head {-# INLINE merge #-} -- | A version of merge which operates on chunks instead of elements. -- -- mergeByChunks offers more control than 'merge'. 'merge' terminates -- when the first stream terminates, however mergeByChunks will continue -- until both streams are exhausted. -- -- 'mergeByChunks' guarantees that both chunks passed to the merge function -- will have the same number of elements, although that number may vary -- between calls. mergeByChunks :: (Nullable c2, Nullable c1 ,NullPoint c2, NullPoint c1 ,LL.ListLike c1 el1, LL.ListLike c2 el2 ,Functor m, Monad m) => (c1 -> c2 -> c3) -- ^ merge function -> (c1 -> c3) -> (c2 -> c3) -> Enumeratee c2 c3 (Iteratee c1 m) a mergeByChunks f f1 f2 = unfoldConvStream iter (0 :: Int) where iter 1 = (1,) . f1 <$> lift getChunk iter 2 = (2,) . f2 <$> getChunk iter _ = do ml1 <- lift chunkLength ml2 <- chunkLength case (ml1, ml2) of (Just l1, Just l2) -> do let tval = min l1 l2 c1 <- lift $ takeFromChunk tval c2 <- takeFromChunk tval return (0, f c1 c2) (Just _, Nothing) -> iter 1 (Nothing, _) -> iter 2 {-# INLINE mergeByChunks #-} -- ------------------------------------------------------------------------ -- Folds -- | Left-associative fold. -- -- The analogue of @List.foldl@ foldl :: (Monad m, LL.ListLike s el, FLL.FoldableLL s el) => (a -> el -> a) -> a -> Iteratee s m a foldl f i = liftI (step i) where step acc (Chunk xs) | LL.null xs = liftI (step acc) | otherwise = liftI (step $ FLL.foldl f acc xs) step acc stream = idone acc stream {-# INLINE foldl #-} -- | Left-associative fold that is strict in the accumulator. -- This function should be used in preference to 'foldl' whenever possible. -- -- The analogue of @List.foldl'@. foldl' :: (Monad m, LL.ListLike s el, FLL.FoldableLL s el) => (a -> el -> a) -> a -> Iteratee s m a foldl' f i = liftI (step i) where step acc (Chunk xs) | LL.null xs = liftI (step acc) | otherwise = liftI (step $! FLL.foldl' f acc xs) step acc stream = idone acc stream {-# INLINE foldl' #-} -- | Variant of foldl with no base case. Requires at least one element -- in the stream. -- -- The analogue of @List.foldl1@. foldl1 :: (Monad m, LL.ListLike s el, FLL.FoldableLL s el) => (el -> el -> el) -> Iteratee s m el foldl1 f = liftI step where step (Chunk xs) -- After the first chunk, just use regular foldl. | LL.null xs = liftI step | otherwise = foldl f $ FLL.foldl1 f xs step stream = icont step (Just (setEOF stream)) {-# INLINE foldl1 #-} -- | Strict variant of 'foldl1'. foldl1' :: (Monad m, LL.ListLike s el, FLL.FoldableLL s el) => (el -> el -> el) -> Iteratee s m el foldl1' f = liftI step where step (Chunk xs) -- After the first chunk, just use regular foldl'. | LL.null xs = liftI step | otherwise = foldl' f $ FLL.foldl1 f xs step stream = icont step (Just (setEOF stream)) {-# INLINE foldl1' #-} -- | Sum of a stream. sum :: (Monad m, LL.ListLike s el, Num el) => Iteratee s m el sum = liftI (step 0) where step acc (Chunk xs) | LL.null xs = liftI (step acc) | otherwise = liftI (step $! acc + LL.sum xs) step acc str = idone acc str {-# INLINE sum #-} -- | Product of a stream. product :: (Monad m, LL.ListLike s el, Num el) => Iteratee s m el product = liftI (step 1) where step acc (Chunk xs) | LL.null xs = liftI (step acc) | otherwise = liftI (step $! acc * LL.product xs) step acc str = idone acc str {-# INLINE product #-} -- ------------------------------------------------------------------------ -- Zips -- |Enumerate two iteratees over a single stream simultaneously. -- Deprecated, use `Data.Iteratee.ListLike.zip` instead. -- -- Compare to @zip@. {-# DEPRECATED enumPair "use Data.Iteratee.ListLike.zip" #-} enumPair :: (Monad m, Nullable s, LL.ListLike s el) => Iteratee s m a -> Iteratee s m b -> Iteratee s m (a, b) enumPair = zip -- |Enumerate two iteratees over a single stream simultaneously. -- -- Compare to @List.zip@. zip :: (Monad m, Nullable s, LL.ListLike s el) => Iteratee s m a -> Iteratee s m b -> Iteratee s m (a, b) zip x0 y0 = do -- need to check if both iteratees are initially finished. If so, -- we don't want to push a chunk which will be dropped (a', x') <- lift $ runIter x0 od oc (b', y') <- lift $ runIter y0 od oc case checkDone a' b' of Just (Right (a,b,s)) -> idone (a,b) s -- 's' may be EOF, needs to stay Just (Left (Left a)) -> liftM (a,) y' Just (Left (Right b)) -> liftM (,b) x' Nothing -> liftI (step x' y') where step x y (Chunk xs) | nullC xs = liftI (step x y) step x y (Chunk xs) = do (a', x') <- lift $ (\i -> runIter i od oc) =<< enumPure1Chunk xs x (b', y') <- lift $ (\i -> runIter i od oc) =<< enumPure1Chunk xs y case checkDone a' b' of Just (Right (a,b,s)) -> idone (a,b) s Just (Left (Left a)) -> liftM (a,) y' Just (Left (Right b)) -> liftM (,b) x' Nothing -> liftI (step x' y') step x y (EOF err) = joinIM $ case err of Nothing -> (liftM2.liftM2) (,) (enumEof x) (enumEof y) Just e -> (liftM2.liftM2) (,) (enumErr e x) (enumErr e y) od a s = return (Just (a, s), idone a s) oc k e = return (Nothing , icont k e) checkDone r1 r2 = case (r1, r2) of (Just (a, s1), Just (b,s2)) -> Just $ Right (a, b, shorter s1 s2) (Just (a, _), Nothing) -> Just . Left $ Left a (Nothing, Just (b, _)) -> Just . Left $ Right b (Nothing, Nothing) -> Nothing shorter c1@(Chunk xs) c2@(Chunk ys) | LL.length xs < LL.length ys = c1 | otherwise = c2 shorter e@(EOF _) _ = e shorter _ e@(EOF _) = e {-# INLINE zip #-} zip3 :: (Monad m, Nullable s, LL.ListLike s el) => Iteratee s m a -> Iteratee s m b -> Iteratee s m c -> Iteratee s m (a, b, c) zip3 a b c = zip a (zip b c) >>= \(r1, (r2, r3)) -> return (r1, r2, r3) {-# INLINE zip3 #-} zip4 :: (Monad m, Nullable s, LL.ListLike s el) => Iteratee s m a -> Iteratee s m b -> Iteratee s m c -> Iteratee s m d -> Iteratee s m (a, b, c, d) zip4 a b c d = zip a (zip3 b c d) >>= \(r1, (r2, r3, r4)) -> return (r1, r2, r3, r4) {-# INLINE zip4 #-} zip5 :: (Monad m, Nullable s, LL.ListLike s el) => Iteratee s m a -> Iteratee s m b -> Iteratee s m c -> Iteratee s m d -> Iteratee s m e -> Iteratee s m (a, b, c, d, e) zip5 a b c d e = zip a (zip4 b c d e) >>= \(r1, (r2, r3, r4, r5)) -> return (r1, r2, r3, r4, r5) {-# INLINE zip5 #-} -- | Enumerate over two iteratees in parallel as long as the first iteratee -- is still consuming input. The second iteratee will be terminated with EOF -- when the first iteratee has completed. An example use is to determine -- how many elements an iteratee has consumed: -- -- > snd <$> enumWith (dropWhile (<5)) length -- -- Compare to @zip@ enumWith :: (Monad m, Nullable s, LL.ListLike s el) => Iteratee s m a -> Iteratee s m b -> Iteratee s m (a, b) enumWith i1 i2 = do -- as with zip, first check to see if the initial iteratee is complete, -- otherwise data would be dropped. -- running the second iteratee as well to prevent a monadic effect mismatch -- although I think that would be highly unlikely to happen in common -- code (a', x') <- lift $ runIter i1 od oc (_, y') <- lift $ runIter i2 od oc case a' of Just (a, s) -> flip idone s =<< lift (liftM (a,) $ run i2) Nothing -> go x' y' where od a s = return (Just (a, s), idone a s) oc k e = return (Nothing , icont k e) getUsed xs (Chunk ys) = LL.take (LL.length xs - LL.length ys) xs getUsed xs (EOF _) = xs go x y = liftI step where step (Chunk xs) | nullC xs = liftI step step (Chunk xs) = do (a', x') <- lift $ (\i -> runIter i od oc) =<< enumPure1Chunk xs x case a' of Just (a, s) -> do b <- lift $ run =<< enumPure1Chunk (getUsed xs s) y idone (a, b) s Nothing -> lift (enumPure1Chunk xs y) >>= go x' step (EOF err) = joinIM $ case err of Nothing -> (liftM2.liftM2) (,) (enumEof x) (enumEof y) Just e -> (liftM2.liftM2) (,) (enumErr e x) (enumErr e y) {-# INLINE enumWith #-} -- |Enumerate a list of iteratees over a single stream simultaneously -- and discard the results. This is a different behavior than Prelude's -- sequence_ which runs iteratees in the list one after the other. -- -- Compare to @Prelude.sequence_@. sequence_ :: (Monad m, LL.ListLike s el, Nullable s) => [Iteratee s m a] -> Iteratee s m () sequence_ = self where self is = liftI step where step (Chunk xs) | LL.null xs = liftI step step s@(Chunk _) = do -- give a chunk to each iteratee is' <- lift $ mapM (enumChunk s) is -- filter done iteratees is'' <- lift $ catMaybes `liftM` mapM checkIfDone is' if Prelude.null is'' then idone () <=< remainingStream $ is' else self is'' step s@(EOF _) = do s' <- remainingStream <=< lift $ mapM (enumChunk s) is case s' of EOF (Just e) -> throwErr e _ -> idone () s' checkIfDone i = runIter i (\_ _ -> return Nothing) (\k e -> return $ Just $ icont k e) -- returns the unconsumed part of the stream; "sequence_ is" consumes as -- much of the stream as the iteratee in is that consumes the most; e.g. -- sequence_ [I.head, I.last] consumes whole stream remainingStream :: (Monad m, Nullable s, LL.ListLike s el) => [Iteratee s m a] -> Iteratee s m (Stream s) remainingStream is = lift $ return . Prelude.foldl1 shorter <=< mapM (\i -> runIter i od oc) $ is where od _ s = return s oc _ e = return $ case e of Nothing -> mempty _ -> EOF e -- return the shorter one of two streams; errors are propagated with the -- priority given to the "left" shorter c1@(Chunk xs) c2@(Chunk ys) | LL.length xs < LL.length ys = c1 | otherwise = c2 shorter (EOF e1 ) (EOF e2 ) = EOF (e1 `mplus` e2) shorter e@(EOF _) _ = e shorter _ e@(EOF _) = e -- ------------------------------------------------------------------------ -- Enumerators -- |The pure n-chunk enumerator -- It passes a given stream of elements to the iteratee in @n@-sized chunks. enumPureNChunk :: (Monad m, LL.ListLike s el) => s -> Int -> Enumerator s m a enumPureNChunk str n iter | LL.null str = return iter | n > 0 = enum' str iter | otherwise = error $ "enumPureNChunk called with n==" ++ show n where enum' str' iter' | LL.null str' = return iter' | otherwise = let (s1, s2) = LL.splitAt n str' on_cont k Nothing = enum' s2 . k $ Chunk s1 on_cont k e = return $ icont k e in runIter iter' idoneM on_cont {-# INLINE enumPureNChunk #-} -- ------------------------------------------------------------------------ -- Monadic functions -- | Map a monadic function over the elements of the stream and ignore the -- result. mapM_ :: (Monad m, LL.ListLike s el, Nullable s) => (el -> m b) -> Iteratee s m () mapM_ f = liftI step where step (Chunk xs) | LL.null xs = liftI step step (Chunk xs) = lift (LL.mapM_ f xs) >> liftI step step s@(EOF _) = idone () s {-# INLINE mapM_ #-} -- |The analogue of @Control.Monad.foldM@ foldM :: (Monad m, LL.ListLike s b, Nullable s) => (a -> b -> m a) -> a -> Iteratee s m a foldM f e = liftI step where step (Chunk xs) | LL.null xs = liftI step step (Chunk xs) = do x <- lift $ f e (LL.head xs) joinIM $ enumPure1Chunk (LL.tail xs) (foldM f x) step (EOF _) = return e {-# INLINE foldM #-}