streamly/Changelog.md

Unreleased

Breaking changes

• Some prelude functions, to whom concurrency capability has been added, will now require a MonadAsync constraint.

Bug Fixes

• Fixed a race due to which, in a rare case, we might block indefinitely on an MVar due to a lost wakeup.
• Fixed an issue in adaptive concurrency. The issue caused us to stop creating more worker threads in some cases due to a race. This would not cause any functional issue but would reduce concurrency in some cases.

Enhancements

• Added a concurrent lookahead stream type Ahead
• Added fromFoldableM API that creates a stream from a container of monadic actions
• Monadic stream generation functions consM, |:, unfoldrM, replicateM, repeatM, iterateM and fromFoldableM can now generate streams concurrently when used with concurrent stream types.
• Monad transformation functions mapM and sequence can now map actions concurrently when used at appropriate stream types.
• Added concurrent function application operators to run stages of a stream processing function application pipeline concurrently.
• Added two functions mapMaybe and mapMaybeM.

0.2.1

Bug Fixes

• Fixed a bug that caused some transformation ops to return incorrect results when used with concurrent streams. The affected ops are take, filter, takeWhile, drop, dropWhile, and reverse.

0.2.0

Breaking changes

• Changed the semantics of the Semigroup instance for InterleavedT, AsyncT and ParallelT. The new semantics are as follows:

  • For InterleavedT, <> operation interleaves two streams
  • For AsyncT, <> now concurrently merges two streams in a left biased manner using demand based concurrency.
  • For ParallelT, the <> operation now concurrently meges the two streams in a fairly parallel manner.

  To adapt to the new changes, replace <> with serial wherever it is used for stream types other than StreamT.

• Remove the Alternative instance. To adapt to this change replace any usage of <|> with parallel and empty with nil.

• Stream type now defaults to the SerialT type unless explicitly specified using a type combinator or a monomorphic type. This change reduces puzzling type errors for beginners. It includes the following two changes:

  • Change the type of all stream elimination functions to use SerialT instead of a polymorphic type. This makes sure that the stream type is always fixed at all exits.
  • Change the type combinators (e.g. parallely) to only fix the argument stream type and the output stream type remains polymorphic.

  Stream types may have to be changed or type combinators may have to be added or removed to adapt to this change.

• Change the type of foldrM to make it consistent with foldrM in base.

• async is renamed to mkAsync and async is now a new API with a different meaning.

• ZipAsync is renamed to ZipAsyncM and ZipAsync is now ZipAsyncM specialized to the IO Monad.

• Remove the MonadError instance as it was not working correctly for parallel compositions. Use MonadThrow instead for error propagation.

• Remove Num/Fractional/Floating instances as they are not very useful. Use fmap and liftA2 instead.

Deprecations

• Deprecate and rename the following symbols:
  • Streaming to IsStream
  • runStreaming to runStream
  • StreamT to SerialT
  • InterleavedT to WSerialT
  • ZipStream to ZipSerialM
  • ZipAsync to ZipAsyncM
  • interleaving to wSerially
  • zipping to zipSerially
  • zippingAsync to zipAsyncly
  • <=> to wSerial
  • <| to async
  • each to fromFoldable
  • scan to scanx
  • foldl to foldx
  • foldlM to foldxM
• Deprecate the following symbols for future removal:
  • runStreamT
  • runInterleavedT
  • runAsyncT
  • runParallelT
  • runZipStream
  • runZipAsync

Enhancements

• Add the following functions:
  • consM and |: operator to construct streams from monadic actions
  • once to create a singleton stream from a monadic action
  • repeatM to construct a stream by repeating a monadic action
  • scanl' strict left scan
  • foldl' strict left fold
  • foldlM' strict left fold with a monadic fold function
  • serial run two streams serially one after the other
  • async run two streams asynchronously
  • parallel run two streams in parallel (replaces <|>)
  • WAsyncT stream type for BFS version of AsyncT composition
• Add simpler stream types that are specialized to the IO monad
• Put a bound (1500) on the output buffer used for asynchronous tasks
• Put a limit (1500) on the number of threads used for Async and WAsync types

0.1.2

Enhancements

• Add iterate, iterateM stream operations

Bug Fixes

• Fixed a bug that casued unexpected behavior when pure was used to inject values in Applicative composition of ZipStream and ZipAsync types.

0.1.1

Enhancements

• Make cons right associative and provide an operator form .: for it
• Add null, tail, reverse, replicateM, scan stream operations
• Improve performance of some stream operations (foldl, dropWhile)

Bug Fixes

• Fix the product operation. Earlier, it always returned 0 due to a bug
• Fix the last operation, which returned Nothing for singleton streams

0.1.0

• Initial release