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GHC 9.10.3 · lts/ghc-9.10.x · c74966e · 2026-09-27

Modulestreamly-0.10.1Haskell2010

Streamly.Internal.Data.Unfold.Prelude

  • 6 values
  • Packagestreamly-0.10.1
  • Exports6
  • LanguageHaskell2010
  • LicenceBSD-3-Clause
  • SourceException.hs
valuefinally
  1. :: (MonadAsync m, MonadCatch m)
  2. => a -> m c
  3. -> Unfold m a b
  4. -> Unfold m a b
#

Unfold the input a using Unfold m a b, run an action on a whenever the unfold stops normally, aborts due to an exception or if it is garbage collected after a partial lazy evaluation.

The semantics of the action a -> m c are similar to the cleanup action semantics in bracket.

finally release = bracket return release

See also finally_

Inhibits stream fusion

Pre-release

valuebracket
  1. :: (MonadAsync m, MonadCatch m)
  2. => a -> m c
  3. -> c -> m d
  4. -> Unfold m c b
  5. -> Unfold m a b
#

Run the alloc action a -> m c with async exceptions disabled but keeping blocking operations interruptible (see mask). Use the output c as input to Unfold m c b to generate an output stream.

c is usually a resource under the state of monad m, e.g. a file handle, that requires a cleanup after use. The cleanup action c -> m d, runs whenever the stream ends normally, due to a sync or async exception or if it gets garbage collected after a partial lazy evaluation.

bracket only guarantees that the cleanup action runs, and it runs with async exceptions enabled. The action must ensure that it can successfully cleanup the resource in the face of sync or async exceptions.

When the stream ends normally or on a sync exception, cleanup action runs immediately in the current thread context, whereas in other cases it runs in the GC context, therefore, cleanup may be delayed until the GC gets to run.

See also: bracket_, gbracket

Inhibits stream fusion

Pre-release

valueafter :: MonadRunInIO m => (a -> m c) -> Unfold m a b -> Unfold m a b
#

Unfold the input a using Unfold m a b, run an action on a whenever the unfold stops normally, or if it is garbage collected after a partial lazy evaluation.

The semantics of the action a -> m c are similar to the cleanup action semantics in bracket.

See also after_

Pre-release

valuegbracket
  1. :: MonadRunInIO m
  2. => (a -> m c)

    before

  3. -> (c -> m d)

    after, on normal stop, or GC

  4. -> Unfold m (c, e) b

    on exception

  5. -> (forall s. m s -> m (Either e s))

    try (exception handling)

  6. -> Unfold m c b

    unfold to run

  7. -> Unfold m a b
#

Run the alloc action a -> m c with async exceptions disabled but keeping blocking operations interruptible (see mask). Use the output c as input to Unfold m c b to generate an output stream. When unfolding use the supplied try operation forall s. m s -> m (Either e s) to catch synchronous exceptions. If an exception occurs run the exception handling unfold Unfold m (c, e) b.

The cleanup action c -> m d, runs whenever the stream ends normally, due to a sync or async exception or if it gets garbage collected after a partial lazy evaluation. See bracket for the semantics of the cleanup action.

gbracket can express all other exception handling combinators.

Inhibits stream fusion

Pre-release