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bracket :: IO a -> (a -> IO b) -> (a -> IO c) -> IO cghc-lib-parser GHC.Utils.Exception When you want to acquire a resource, do some work with it, and then release the resource, it is a good idea to use bracket, because bracket will install the necessary exception handler to release the resource in the event that an exception is raised during the computation. If an exception is raised, then bracket will re-raise the exception (after performing the release). A common example is opening a file:
bracket (openFile "filename" ReadMode) (hClose) (\fileHandle -> do { ... })
The arguments to bracket are in this order so that we can partially apply it, e.g.:withFile name mode = bracket (openFile name mode) hClose
Bracket wraps the release action with mask, which is sufficient to ensure that the release action executes to completion when it does not invoke any interruptible actions, even in the presence of asynchronous exceptions. For example, hClose is uninterruptible when it is not racing other uses of the handle. Similarly, closing a socket (from "network" package) is also uninterruptible under similar conditions. An example of an interruptible action is killThread. Completion of interruptible release actions can be ensured by wrapping them in uninterruptibleMask_, but this risks making the program non-responsive to Control-C, or timeouts. Another option is to run the release action asynchronously in its own thread:void $ uninterruptibleMask_ $ forkIO $ do { ... }
The resource will be released as soon as possible, but the thread that invoked bracket will not block in an uninterruptible state.bracket :: MonadSafe m => Base m a -> (a -> Base m b) -> (a -> m c) -> m cpipes-safe Pipes.Safe Analogous to bracket from Control.Monad.Catch, except this also protects against premature termination
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checkers Test.QuickCheck.Instances.Char Generates one or other of '[' and ']'.
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effectful-core Effectful.Exception Lifted bracket.
bracket :: Parser a -> Parser b -> Parser c -> Parser bpolyparse Text.ParserCombinators.HuttonMeijer No documentation available.
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polyparse Text.ParserCombinators.HuttonMeijerWallace No documentation available.
bracket :: PolyParse p => p bra -> p ket -> p a -> p apolyparse Text.ParserCombinators.Poly.Base Parse a bracketed item, discarding the brackets. If everything matches except the closing bracket, the whole parse fails soft, which can give less-than-satisfying error messages. If you want better error messages, try calling with e.g. bracket open (commit close) item
bracket :: PolyParse p => p bra -> p ket -> p a -> p apolyparse Text.ParserCombinators.Poly.StateLazy Parse a bracketed item, discarding the brackets. If everything matches except the closing bracket, the whole parse fails soft, which can give less-than-satisfying error messages. If you want better error messages, try calling with e.g. bracket open (commit close) item
bracket :: forall (es :: Effects) a b . Eff es a -> (a -> Eff es ()) -> (a -> Eff es b) -> Eff es bbluefin-internal Bluefin.Internal bracket acquire release body: acquire a resource, perform the body with it, and release the resource even if body threw an exception. This is essentially the same as Control.Exception.bracket, whose documentation you can inspect for further details. bracket has a very general type that does not require es to contain an exception or IO effect. The reason that this is safe is:
- While bracket does catch exceptions, this is unobservable, since the exception is re-thrown; the cleanup action happens unconditionally; and no part of it gets access to the thrown exception.
- Eff itself is able to guarantee that any exceptions thrown in the body will be actually thrown before bracket exits. This is inherited from the fact that Eff is a wrapper around IO.
bracket :: MonadPeelIO m => m a -> (a -> m b) -> (a -> m c) -> m cmonad-peel Control.Exception.Peel Generalized version of bracket. Note, any monadic side effects in m of the "release" computation will be discarded; it is run only for its side effects in IO.