https://github.com/fused-effects/fused-effects-exceptions

Handle exceptions thrown in IO with fused-effects.
https://github.com/fused-effects/fused-effects-exceptions

Last synced: about 2 months ago
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Handle exceptions thrown in IO with fused-effects.

• Host: GitHub
• URL: https://github.com/fused-effects/fused-effects-exceptions
• Owner: fused-effects
• License: bsd-3-clause
• Created: 2019-03-19T14:22:38.000Z (almost 6 years ago)
• Default Branch: master
• Last Pushed: 2022-07-15T15:10:52.000Z (over 2 years ago)
• Last Synced: 2024-05-03T07:26:33.267Z (8 months ago)
• Language: Haskell
• Size: 63.5 KB
• Stars: 8
• Watchers: 4
• Forks: 4
• Open Issues: 2
• Metadata Files:
  • Readme: README.lhs
  • Changelog: ChangeLog.md
  • License: LICENSE

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# fused-effects-exceptions

[![Hackage](https://img.shields.io/hackage/v/fused-effects-exceptions.svg)](https://hackage.haskell.org/package/fused-effects-exceptions)

[![BSD3 license](https://img.shields.io/badge/license-BSD3-blue.svg)](LICENSE)

[![Build Status](https://action-badges.now.sh/fused-effects/fused-effects-exceptions)](https://github.com/fused-effects/fused-effects-exceptions/actions)

This package provides `Control.Effect.Exception`, a module that wraps the [`Control.Exception`](http://hackage.haskell.org/package/base/docs/Control-Exception.html) API from `base` with the vocabulary provided by the [`fused-effects`](http://hackage.haskell.org/package/fused-effects) library. These functions interact with GHC's support for dynamic exceptions, including functions like `catch` for exception handling and `bracket` for resource management.

Please be aware that injudicious use of these functions may provoke surprising interactions with carriers that thread a monadic state as a parameter, à la the `Control.Carrier.State` types provided by `fused-effects`. For example, a function like `finally`, which does not thread any state from its body to its handler block, may discard state writes in cleanup handlers:

```haskell

discardsState :: IO Char

discardsState = execState 'a' ((throwIO (userError "urk") `finally` put @Char 'z')

    `catch` (\(_ :: IOException) -> pure ()))

```

Though the `put @Char 'z'` statement is evaluated, its effect is ultimately discarded; the result of executing the above is `'a'`. If this behavior is a concern, use the `Control.Carrier.State.IORef` carrier from `fused-effects` itself.

Prior versions of this package provided a `Catch` effect; this has been excised in favor of the more-general `Control.Effect.Exception`, which provides more functionality without requiring any additional carriers beyond a `Lift IO` effect.