content: {-# LANGUAGE CPP #-}
  -- |
  -- Module      : Streamly.Data.Stream
  -- Copyright   : (c) 2017 Composewell Technologies
  --
  -- License     : BSD3
  -- Maintainer  : streamly@composewell.com
  -- Stability   : released
  -- Portability : GHC
  --
  -- The 'Stream' type represents a producer of a sequence of values. Its dual,
  -- 'Streamly.Data.Fold.Fold', represents a consumer. While both types support
  -- similar transformations, the key difference is that only 'Stream' can
  -- compose multiple producers, and only 'Fold' can compose multiple consumers.
  --
  -- == Console Echo Example
  --
  -- To get you started, here is an example of a program which reads lines from
  -- console and writes them back to the console.
  --
  -- >>> import Data.Function ((&))
  -- >>> :{
  -- echo =
  --  Stream.repeatM getLine       -- Stream IO String
  --      & Stream.mapM putStrLn   -- Stream IO ()
  --      & Stream.fold Fold.drain -- IO ()
  -- :}
  --
  -- This is a simple example of a declarative representation of an imperative
  -- loop using streaming combinators.
  -- In this example, 'repeatM' generates an infinite stream of 'String's by
  -- repeatedly performing the 'getLine' IO action. 'mapM' then applies
  -- 'putStrLn' on each element in the stream converting it to stream of '()'.
  -- Finally, 'Streamly.Data.Fold.drain' 'fold's the stream to IO discarding the
  -- () values, thus producing only effects.
  --
  -- This gives you an idea about how we can program declaratively by
  -- representing loops using streams. Compare this declarative loopless approach
  -- with an imperative approach using a @while@ loop for writing the same
  -- program. In this module, you can find all "Data.List"-like functions and
  -- many more powerful combinators to perform common programming tasks.
  --
  -- == Static Stream Fusion
  --
  -- The 'Stream' type represents streams as state machines. When composed
  -- statically, these state machines fuse together at compile time, eliminating
  -- intermediate data structures and function calls. This results in the
  -- generation of tight, efficient loops comparable to those written in
  -- low-level languages like C. For instance, in the earlier example, operations
  -- like 'repeatM' and 'mapM' are written as separate fragments but fuse into a
  -- single, optimized loop.
  --
  -- The primary goal of the 'Stream' type is to build highly efficient streams
  -- via compile-time fusion of modular loop fragments. However, this technique
  -- comes with trade-offs and should be used with care. Stream /construction/
  -- operations such as 'cons', 'append', 'interleave', 'mergeBy', and 'zipWith'
  -- work extremely well at a small scale. But at a large scale, their
  -- performance degrades due to O(n^2) complexity, where @n@ is the number of
  -- compositions.
  --
  -- Therefore, it's best to generate a fused stream in one go, if possible.
  -- While using a small number of composition operations is absolutely fine,
  -- avoid using large number of composition operations. For example, do not try
  -- to construct a fused 'Stream' by using `cons` rescursively. However, you can
  -- use 'Streamly.Data.StreamK.cons' and any other construction operations on
  -- the CPS 'StreamK' type without any problem. The CPS construction operations
  -- have linear (O(n)) performance characteristics and scale much better, though
  -- they are not as efficient as fused streams due to function call overhead at
  -- each step.
  --
  -- When used correctly, the fused 'Stream' type can be 10x to 100x faster
  -- than CPS-based streams, depending on the use case.
  --
  -- __Rule of Thumb:__ Use the fused 'Stream' type when the number of
  -- compositions is small and they are static or compile-time. Use the CPS-based
  -- 'StreamK' type when the number of compositions is large or potentially
  -- infinite, and they are dynamic or composed at runtime. Both types are fully
  -- interconvertible, allowing you to choose the best tool for each part of your
  -- pipeline.
  --
  -- == Better and Effectful Lists
  --
  -- This module offers operations analogous to standard Haskell lists from the
  -- @base@ package. Streams can be viewed as a generalization of lists —
  -- providing all the functionality of standard lists, plus additional
  -- capabilities such as effectful operations and improved performance through
  -- stream fusion. They can easily replace lists in most contexts, and go
  -- beyond where lists fall short.
  --
  -- For instance, a common limitation of lists is the inability to perform IO
  -- actions (e.g., printing) at arbitrary points during processing. Streams
  -- naturally support such effectful operations.
  --
  -- As discussed in the fusion section above, while the 'Stream' type is not
  -- consable and appendable at scale, the 'StreamK' type is consable and
  -- appendable at scale.
  --
  -- == Non-determinism and List Transformers
  --
  -- Streamly does not provide a 'ListT' like Monad instance but it provides all
  -- the equivalent functionality and more. We do not provide a Monad instance
  -- for streams, as there are many possible ways to define the bind operation.
  -- Instead, we offer bind-style operations such as 'concatFor', 'concatForM',
  -- and their variants (e.g. fair interleaving and breadth-first nesting). These
  -- can be used for convenient ListT-style stream composition. Additionally, we
  -- provide applicative-style cross product operations like 'cross' and its
  -- variants which are many times faster than the monad style operations.
  --
  -- == Logic Programming
  --
  -- Streamly does not provide a 'LogicT'-style Monad instance, but it offers all
  -- the equivalent functionality—and more. Operations like 'fairCross' and
  -- 'fairConcatFor' nest outer and inner streams fairly, ensuring that no stream
  -- is starved when exploring cross products.
  --
  -- This enables balanced exploration across all dimensions in backtracking
  -- problems, while also supporting infinite streams. It effectively replaces the
  -- core functionality of 'LogicT' from the @logict@ package, with significantly
  -- better performance. In particular, it avoids the quadratic slowdown seen with
  -- @observeMany@, and the applicative 'fairCross' runs many times faster,
  -- achieving loop nesting performance comparable to C.
  
  -- == Additional Resources
  --
  -- The combinators in this module support /serial/ composition of streams.
  -- For /concurrent/ composition of streams, refer to
  -- "Streamly.Data.Stream.Prelude" in the @streamly@ package.
  --
  -- For more, yet unreleased functions, try: "Streamly.Internal.Data.Stream".
  --
  -- For real-world examples, visit:
  -- <https://github.com/composewell/streamly-examples>.
  --
  
  module Streamly.Data.Stream
      (
      -- * Setup
      -- | To execute the code examples provided in this module in ghci, please
      -- run the following commands first.
      --
      -- $setup
  
      -- * Overview
      -- $overview
  
      -- * The Stream Type
        Stream
  
      -- * Construction
      -- | Functions ending in the general shape @b -> Stream m a@.
      --
      -- Useful Idioms:
      --
      -- >>> fromIndices f = fmap f $ Stream.enumerateFrom 0
      -- >>> fromIndicesM f = Stream.mapM f $ Stream.enumerateFrom 0
      -- >>> fromListM = Stream.sequence . Stream.fromList
      -- >>> fromFoldable = StreamK.toStream . StreamK.fromFoldable
      -- >>> fromFoldableM = Stream.sequence . fromFoldable
  
      -- ** Primitives
      -- | These primitives are meant to statically fuse a small number of stream
      -- elements. The 'Stream' type is never constructed at large scale using
      -- these primitives. Use 'StreamK' if you need to construct a stream from
      -- primitives.
      , nil
      , nilM
      , cons
      , consM
  
      -- ** Unfolding
      -- | 'unfoldrM' is the most general way of generating a stream efficiently.
      -- All other generation operations can be expressed using it.
      , unfoldr
      , unfoldrM
  
      -- ** Singleton
      , fromPure
      , fromEffect
  
      -- ** Iteration
      -- | Generate a monadic stream from a seed value or values.
      --
      , iterate
      , iterateM
      , repeat
      , repeatM
      , replicate
      , replicateM
  
      -- ** Enumeration
      -- | 'Enumerable' type class is to streams as 'Enum' is to lists. Enum
      -- provides functions to generate a list, Enumerable provides similar
      -- functions to generate a stream instead.
      --
      -- It is much more efficient to use 'Enumerable' directly than enumerating
      -- to a list and converting it to stream. The following works but is not
      -- particularly efficient:
      --
      -- >>> f from next = Stream.fromList $ Prelude.enumFromThen from next
      --
      -- Note: For lists, using enumeration functions e.g. 'Prelude.enumFromThen'
      -- turns out to be slightly faster than the idioms like @[from, then..]@.
  
      , Enumerable (..)
      , enumerate
      , enumerateTo
  
      -- ** From Containers
      -- | Convert an input structure, container or source into a stream. All of
      -- these can be expressed in terms of primitives.
      , fromList
  
      -- ** From Unfolds
      -- | Most of the above stream generation operations can also be expressed
      -- using the corresponding unfolds in the "Streamly.Data.Unfold" module.
      , unfold -- XXX rename to fromUnfold?
  
      -- * Elimination
      -- | Functions ending in the general shape @Stream m a -> m b@ or @Stream m
      -- a -> m (b, Stream m a)@
      --
  
  -- EXPLANATION: In imperative terms a fold can be considered as a loop over the stream
  -- that reduces the stream to a single value.
  -- Left and right folds both use a fold function @f@ and an identity element
  -- @z@ (@zero@) to deconstruct a recursive data structure and reconstruct a
  -- new data structure. The new structure may be a recursive construction (a
  -- container) or a non-recursive single value reduction of the original
  -- structure.
  --
  -- Both right and left folds are mathematical duals of each other, they are
  -- functionally equivalent.  Operationally, a left fold on a left associated
  -- structure behaves exactly in the same way as a right fold on a right
  -- associated structure. Similarly, a left fold on a right associated structure
  -- behaves in the same way as a right fold on a left associated structure.
  -- However, the behavior of a right fold on a right associated structure is
  -- operationally different (even though functionally equivalent) than a left
  -- fold on the same structure.
  --
  -- On right associated structures like Haskell @cons@ lists or Streamly
  -- streams, a lazy right fold is naturally suitable for lazy recursive
  -- reconstruction of a new structure, while a strict left fold is naturally
  -- suitable for efficient reduction. In right folds control is in the hand of
  -- the @puller@ whereas in left folds the control is in the hand of the
  -- @pusher@.
  --
  -- The behavior of right and left folds are described in detail in the
  -- individual fold's documentation.  To illustrate the two folds for right
  -- associated @cons@ lists:
  --
  -- > foldr :: (a -> b -> b) -> b -> [a] -> b
  -- > foldr f z [] = z
  -- > foldr f z (x:xs) = x `f` foldr f z xs
  -- >
  -- > foldl :: (b -> a -> b) -> b -> [a] -> b
  -- > foldl f z [] = z
  -- > foldl f z (x:xs) = foldl f (z `f` x) xs
  --
  -- @foldr@ is conceptually equivalent to:
  --
  -- > foldr f z [] = z
  -- > foldr f z [x] = f x z
  -- > foldr f z xs = foldr f (foldr f z (tail xs)) [head xs]
  --
  -- @foldl@ is conceptually equivalent to:
  --
  -- > foldl f z [] = z
  -- > foldl f z [x] = f z x
  -- > foldl f z xs = foldl f (foldl f z (init xs)) [last xs]
  --
  -- Left and right folds are duals of each other.
  --
  -- @
  -- foldr f z xs = foldl (flip f) z (reverse xs)
  -- foldl f z xs = foldr (flip f) z (reverse xs)
  -- @
  --
  -- More generally:
  --
  -- @
  -- foldr f z xs = foldl g id xs z where g k x = k . f x
  -- foldl f z xs = foldr g id xs z where g x k = k . flip f x
  -- @
  --
  
  -- NOTE: Folds are inherently serial as each step needs to use the result of
  -- the previous step. However, it is possible to fold parts of the stream in
  -- parallel and then combine the results using a monoid.
  
      -- ** Primitives
      -- Consuming a part of the stream and returning the rest. Functions
      -- ending in the general shape @Stream m a -> m (b, Stream m a)@
      , uncons
  
      -- ** Strict Left Folds
      -- XXX Need to have a general parse operation here which can be used to
      -- express all others.
      , fold -- XXX rename to run? We can have a Stream.run and Fold.run.
      -- XXX fold1 can be achieved using Monoids or Refolds.
      -- XXX We can call this just "break" and parseBreak as "munch"
      , foldBreak
  
      -- XXX should we have a Fold returning function in stream module?
      -- , foldAdd
      -- , buildl
  
      -- ** Parsing
      , parse
      , parseBreak
      , parsePos
      , parseBreakPos
  
      -- ** Lazy Right Folds
      -- | Consuming a stream to build a right associated expression, suitable
      -- for lazy evaluation. Evaluation of the input happens when the output of
      -- the fold is evaluated, the fold output is a lazy thunk.
      --
      -- This is suitable for stream transformation operations, for example,
      -- operations like mapping a function over the stream.
      , foldrM
      , foldr
      -- foldr1
  
      -- ** Specific Folds
      -- | Streams are folded using folds in "Streamly.Data.Fold". Here are some
      -- idioms and equivalents of Data.List APIs using folds:
      --
      -- >>> foldlM' f a = Stream.fold (Fold.foldlM' f a)
      -- >>> foldl1' f = Stream.fold (Fold.foldl1' f)
      -- >>> foldl' f a = Stream.fold (Fold.foldl' f a)
      -- >>> drain = Stream.fold Fold.drain
      -- >>> mapM_ f = Stream.fold (Fold.drainMapM f)
      -- >>> length = Stream.fold Fold.length
      -- >>> genericLength = Stream.fold Fold.genericLength
      -- >>> head = Stream.fold Fold.one
      -- >>> last = Stream.fold Fold.latest
      -- >>> null = Stream.fold Fold.null
      -- >>> and = Stream.fold Fold.and
      -- >>> or = Stream.fold Fold.or
      -- >>> any p = Stream.fold (Fold.any p)
      -- >>> all p = Stream.fold (Fold.all p)
      -- >>> sum = Stream.fold Fold.sum
      -- >>> product = Stream.fold Fold.product
      -- >>> maximum = Stream.fold Fold.maximum
      -- >>> maximumBy cmp = Stream.fold (Fold.maximumBy cmp)
      -- >>> minimum = Stream.fold Fold.minimum
      -- >>> minimumBy cmp = Stream.fold (Fold.minimumBy cmp)
      -- >>> elem x = Stream.fold (Fold.elem x)
      -- >>> notElem x = Stream.fold (Fold.notElem x)
      -- >>> lookup x = Stream.fold (Fold.lookup x)
      -- >>> find p = Stream.fold (Fold.find p)
      -- >>> (!?) i = Stream.fold (Fold.index i)
      -- >>> genericIndex i = Stream.fold (Fold.genericIndex i)
      -- >>> elemIndex x = Stream.fold (Fold.elemIndex x)
      -- >>> findIndex p = Stream.fold (Fold.findIndex p)
      --
      -- Some equivalents of Data.List APIs from the Stream module:
      --
      -- >>> head = fmap (fmap fst) . Stream.uncons
      -- >>> tail = fmap (fmap snd) . Stream.uncons
      -- >>> tail = Stream.tail -- unreleased API
      -- >>> init = Stream.init -- unreleased API
      --
      -- A Stream based toList fold implementation is provided below because it
      -- has a better performance compared to the fold.
  
      -- Functions in Data.List, missing here:
      -- unsnoc = Stream.parseBreak (Parser.init Fold.toList)
      -- genericTake
      -- genericDrop
      -- genericSplitAt
      -- genericReplicate
      , toList
  
      -- * Mapping
      -- | Stateless one-to-one transformations. Use 'fmap' for mapping a pure
      -- function on a stream.
  
      -- EXPLANATION:
      -- In imperative terms a map operation can be considered as a loop over
      -- the stream that transforms the stream into another stream by performing
      -- an operation on each element of the stream.
      --
      -- 'map' is the least powerful transformation operation with strictest
      -- guarantees.  A map, (1) is a stateless loop which means that no state is
      -- allowed to be carried from one iteration to another, therefore,
      -- operations on different elements are guaranteed to not affect each
      -- other, (2) is a strictly one-to-one transformation of stream elements
      -- which means it guarantees that no elements can be added or removed from
      -- the stream, it can merely transform them.
      , sequence
      , mapM
      , trace
      , tap
      , delay
  
      -- * Scanning
      -- | Stateful one-to-one transformations.
      --
  
      {-
      -- ** Left scans
      -- | We can perform scans using folds with the 'scan' combinator in the
      -- next section. However, the combinators supplied in this section are
      -- better amenable to stream fusion when combined with other operations.
      -- Note that 'postscan' using folds fuses well and does not require custom
      -- combinators like these.
      , scanl'
      , scanlM'
      , scanl1'
      , scanl1M'
      -}
  
      -- ** Scanning By 'Scanl'
      -- | Useful idioms:
      --
      -- >>> scanl' f z = Stream.scanl (Scanl.mkScanl f z)
      -- >>> scanlM' f z = Stream.scanl (Scanl.mkScanlM f z)
      -- >>> postscanl' f z = Stream.postscanl (Scanl.mkScanl f z)
      -- >>> postscanlM' f z = Stream.postscanl (Scanl.mkScanlM f z)
      -- >>> scanl1' f = Stream.catMaybes . Stream.scanl (Scanl.mkScanl1 f)
      -- >>> scanl1M' f = Stream.catMaybes . Stream.scanl (Scanl.mkScanl1M f)
      , scanl
      , postscanl
      -- XXX postscan1 can be implemented using Monoids or Refolds.
      -- The following scans from Data.List are not provided.
      -- XXX scanl
      -- XXX scanl1
      -- XXX scanr
      -- XXX scanr1
      -- XXX mapAccumL
      -- XXX mapAccumR
      -- XXX inits
      -- XXX tails
  
      -- ** Specific scans
      -- Indexing can be considered as a special type of zipping where we zip a
      -- stream with an index stream.
      , indexed
  
      -- * Insertion
      -- | Add elements to the stream.
      --
      -- >>> insert = Stream.insertBy compare
  
      -- Inserting elements is a special case of interleaving/merging streams.
      , insertBy
      , intersperseM
      , intersperseM_
      , intersperse
  
      -- * Filtering
      -- | Remove elements from the stream.
  
      -- ** Stateless Filters
      -- | 'mapMaybeM' is the most general stateless filtering operation. All
      -- other filtering operations can be expressed using it.
  
      -- EXPLANATION:
      -- In imperative terms a filter over a stream corresponds to a loop with a
      -- @continue@ clause for the cases when the predicate fails.
  
      , mapMaybe
      , mapMaybeM
      , filter
      , filterM
  
      -- Filter and concat
      , catMaybes
      , catLefts
      , catRights
      , catEithers
  
      -- ** Stateful Filters
  
      -- XXX Should use scanr instead of scanlMaybe for filtering.
  
      -- 'scanMaybe' is the most general stateful filtering operation. The
      -- filtering folds (folds returning a 'Maybe' type) in
      -- "Streamly.Internal.Data.Fold" can be used along with 'scanMaybe' to
      -- perform stateful filtering operations in general.
      --
      -- Idioms and equivalents of Data.List APIs:
      --
      -- >>> deleteBy cmp x = Stream.scanMaybe (Fold.deleteBy cmp x)
      -- >>> deleteBy = Stream.deleteBy -- unreleased API
      -- >>> delete = deleteBy (==)
      -- >>> findIndices p = Stream.scanMaybe (Fold.findIndices p)
      -- >>> elemIndices a = findIndices (== a)
      -- >>> uniq = Stream.scanMaybe (Fold.uniqBy (==))
      -- >>> partition p = Stream.fold (Fold.partition Fold.toList Fold.toList) . fmap (if p then Left else Right)
      -- >>> takeLast n s = Stream.fromEffect $ fmap Array.read $ Array.createOfLast n s
      -- , scanlMaybe
      , take
      , takeWhile
      , takeWhileM
      , drop
      , dropWhile
      , dropWhileM
      -- XXX write to an array in reverse and then read in reverse
      -- > dropWhileEnd = reverse . dropWhile p . reverse
  
      -- XXX These are available as scans in folds. We need to check the
      -- performance though. If these are common and we need convenient stream
      -- ops then we can expose these.
  
      -- , deleteBy
      -- , uniq
      -- , uniqBy
  
      -- -- ** Sampling
      -- , strideFromThen
  
      -- -- ** Searching
      -- Finding the presence or location of an element, a sequence of elements
      -- or another stream within a stream.
  
      -- -- ** Searching Elements
      -- , findIndices
      -- , elemIndices
  
      -- * Combining Two Streams
      -- | Note that these operations are suitable for statically fusing a few
      -- streams, they have a quadratic O(n^2) time complexity wrt to the number
      -- of streams. If you want to compose many streams dynamically using binary
      -- combining operations see the corresponding operations in
      -- "Streamly.Data.StreamK".
      --
      -- When fusing more than two streams it is more efficient if the binary
      -- operations are composed as a balanced tree rather than a right
      -- associative or left associative one e.g.:
      --
      -- >>> s1 = Stream.fromList [1,2] `Stream.append` Stream.fromList [3,4]
      -- >>> s2 = Stream.fromList [4,5] `Stream.append` Stream.fromList [6,7]
      -- >>> s = s1 `Stream.append` s2
  
      -- ** Appending
      -- | Equivalent of Data.List append:
      --
      -- >>> (++) = Stream.append
      , append
  
      -- ** Interleaving
      , interleave
  
      -- ** Merging
      , mergeBy
      , mergeByM
  
      -- ** Zipping
      -- | Idioms and equivalents of Data.List APIs:
      --
      -- >>> zip = Stream.zipWith (,)
      -- >>> unzip = Stream.fold (Fold.unzip Fold.toList Fold.toList)
      , zipWith
      , zipWithM
      -- XXX zipWith3,4,5,6,7
      -- XXX unzip3,4,5,6,7
      -- , ZipStream (..)
  
      -- ** Cross Product
      -- XXX The argument order in this operation is such that it seems we are
      -- transforming the first stream using the second stream because the second
      -- stream is evaluated many times or buffered and better be finite, first
      -- stream could potentially be infinite. In the tradition of using the
      -- transformed stream at the end we can have a flipped version called
      -- "crossMap" or "nestWith".
      , crossWith
      , cross
      -- , fairCrossWith
      , fairCross
      -- , joinInner
      -- , CrossStream (..)
  
      -- * Unfold Each
      -- Idioms and equivalents of Data.List APIs:
      --
      -- >>> cycle = Stream.unfoldEach Unfold.fromList . Stream.repeat
      -- >>> unlines = Stream.unfoldEachEndBy '\n'
      -- >>> unwords = Stream.unfoldEachSepBy ' '
      -- >>> unlines = Stream.unfoldEachEndBySeq "\n" Unfold.fromList
      -- >>> unwords = Stream.unfoldEachSepBySeq " " Unfold.fromList
      --
      , unfoldEach
      , bfsUnfoldEach
      , fairUnfoldEach
      , unfoldEachSepBySeq
      , unfoldEachEndBySeq
  
      -- * Stream of streams
      -- | Stream operations like map and filter represent loops in
      -- imperative programming terms. Similarly, the imperative concept of
      -- nested loops are represented by streams of streams. The 'concatMap'
      -- operation represents nested looping.
      --
      -- A 'concatMap' operation loops over the input stream (outer loop),
      -- generating a stream from each element of the stream. Then it loops over
      -- each element of the generated streams (inner loop), collecting them in a
      -- single output stream.
      --
      -- One dimension loops are just a special case of nested loops.  For
      -- example map and filter can be expressed using concatMap:
      --
      -- >>> map f = Stream.concatMap (Stream.fromPure . f)
      -- >>> filter p = Stream.concatMap (\x -> if p x then Stream.fromPure x else Stream.nil)
      --
      -- Idioms and equivalents of Data.List APIs:
      --
      -- >>> concat = Stream.concatMap id
      -- >>> cycle = Stream.concatMap Stream.fromList . Stream.repeat
  
      , concatEffect
      , concatMap
      , concatMapM
      -- , bfsConcatMap
      , fairConcatMap
  
      , concatFor
      -- , bfsConcatFor
      , fairConcatFor
  
      , concatForM
      -- , bfsConcatForM
      , fairConcatForM
  
      -- * Repeated Fold
      -- | Idioms and equivalents of Data.List APIs:
      --
      -- >>> groupsOf n = Stream.foldMany (Fold.take n Fold.toList)
      -- >>> groupBy eq = Stream.groupsWhile eq Fold.toList
      -- >>> groupBy eq = Stream.parseMany (Parser.groupBy eq Fold.toList)
      -- >>> groupsByRolling eq = Stream.parseMany (Parser.groupByRolling eq Fold.toList)
      -- >>> groups = groupBy (==)
      , foldMany
      , groupsOf
      , parseMany
  
      -- * Splitting
      -- | Idioms and equivalents of Data.List APIs:
      --
      -- >>> splitEndBy p f = Stream.foldMany (Fold.takeEndBy p f)
      -- >>> splitEndBy_ p f = Stream.foldMany (Fold.takeEndBy_ p f)
      -- >>> lines = splitEndBy_ (== '\n')
      -- >>> words = Stream.wordsBy isSpace
      -- >>> splitAt n = Stream.fold (Fold.splitAt n Fold.toList Fold.toList)
      -- >>> span p = Parser.splitWith (,) (Parser.takeWhile p Fold.toList) (Parser.fromFold Fold.toList)
      -- >>> break p = span (not . p)
      , splitSepBy_
      , splitSepBySeq_
      , splitEndBySeq
      , splitEndBySeq_
      , wordsBy
  
      -- XXX Should use scanr instead
      -- >>> nub = Stream.fold Fold.toList . Stream.scanMaybe Fold.nub
  
      -- * Buffered Operations
      -- | Operations that require buffering of the stream.
      -- Reverse is essentially a left fold followed by an unfold.
      --
      -- Idioms and equivalents of Data.List APIs:
      --
      -- >>> nub = Stream.ordNub -- unreleased API
      -- >>> sortBy = StreamK.sortBy
      -- >>> sortOn f = StreamK.sortOn -- unreleased API
      -- >>> deleteFirstsBy = Stream.deleteFirstsBy -- unreleased
      -- >>> (\\) = Stream.deleteFirstsBy (==) -- unreleased
      -- >>> intersectBy = Stream.intersectBy -- unreleased
      -- >>> intersect = Stream.intersectBy (==) -- unreleased
      -- >>> unionBy = Stream.unionBy -- unreleased
      -- >>> union = Stream.unionBy (==) -- unreleased
      --
      , reverse
      , unionBy
      -- XXX transpose: write the streams to arrays and then stream transposed.
      -- XXX subsequences
      -- XXX permutations
      -- , nub
      -- , ordNub
      -- , nubBy
  
      -- * Multi-Stream folds
      -- | Operations that consume multiple streams at the same time.
      , eqBy
      , cmpBy
      , isPrefixOf
      , isInfixOf
      -- , isSuffixOf
      -- , isSuffixOfUnbox
      , isSubsequenceOf
  
      -- trimming sequences
      , stripPrefix
      -- , stripSuffix
      -- , stripSuffixUnbox
  
      -- Exceptions and resource management depend on the "exceptions" package
      -- XXX We can have IO Stream operations not depending on "exceptions"
      -- in Exception.Base
  
      -- * Exceptions
      -- | __Scope__: Note that the stream exception handling routines
      -- (catch and handle) observe exceptions only in the stream segment (i.e.
      -- functions with the 'Stream' type) of the pipeline and not in the
      -- consumer segments (i.e. functions with 'Fold' or 'Parser' types). For
      -- example, if we are folding or parsing a stream - any exceptions in the
      -- fold or parser code won't be observed by the stream exception handlers.
      --
      -- Exceptions in the fold code can be handled using similar exception
      -- handling routines found in the "Streamly.Data.Fold" module. To observe
      -- exceptions in the entire pipeline, you can wrap the stream elimination
      -- effect itself in a monad level exception handler (e.g. @Stream.fold
      -- Fold.drain `catch` ...@).
      --
      -- Most of these combinators inhibit stream fusion, therefore, when
      -- possible, they should be called in an outer loop to mitigate the cost.
      -- For example, instead of calling them on a stream of chars call them on a
      -- stream of arrays before flattening it to a stream of chars.
      --
      , onException
      , handle
  
      -- * Resource Management
      -- | 'bracket' is the most general resource management operation, all other
      -- resource management operations can be expressed using it. These
      -- functions have IO suffix because the allocation and cleanup functions
      -- are IO actions. For generalized allocation and cleanup functions, see
      -- the functions without the IO suffix in the @streamly@ package.
      --
      -- __Scope__: Note that these operations bracket only the stream-segment in
      -- a pipeline, they do not cover the stream-consumer (e.g. folds). This
      -- means that if an exception occurs in the consumer of the stream (e.g. in a
      -- fold or parser driven by the stream) then the exception won't be
      -- observed by the stream resource handlers, in such cases the resource
      -- stream cleanup handler runs when the stream is garbage collected.
      --
      -- To observe exceptions in the entire pipline, put a monad level resource
      -- bracket around the stream elimination effect (e.g. around @(Stream.fold
      -- Fold.sum)@).
      --
      -- See also the "Streamly.Control.Exception" module for general
      -- resource management operations in non-stream as well as stream code.
      , before
      , afterIO
      , finallyIO
      , finallyIO'
      , finallyIO''
      , bracketIO
      -- XXX Expose the Control.Exception module as well.
      , bracketIO'
      , bracketIO''
      , bracketIO3
  
      -- * Transforming Inner Monad
  
      , morphInner
      , liftInner
      , runReaderT
      , runStateT
  
      -- * Deprecated
      , scan
      , scanMaybe
      , postscan
      , splitOn
      , unfoldMany
      , intercalate
      , intercalateSuffix
      , chunksOf
      )
  where
  
  import Streamly.Internal.Data.Stream
  import Prelude
         hiding (filter, drop, dropWhile, take, takeWhile, zipWith, foldr,
                 mapM, scanl, sequence, reverse, iterate, foldr1, repeat, replicate,
                 concatMap)
  
  import Streamly.Internal.Data.Unbox (Unbox(..))
  import Control.Monad.IO.Class (MonadIO(..))
  
  import qualified Streamly.Internal.Data.Array.Type as Array
  
  #include "DocTestDataStream.hs"
  
  {-# DEPRECATED chunksOf "Please use chunksOf from the Array module instead." #-}
  {-# INLINE chunksOf #-}
  chunksOf :: forall m a. (MonadIO m, Unbox a)
      => Int -> Stream m a -> Stream m (Array.Array a)
  chunksOf = Array.chunksOf
  