https://github.com/dcastro/safe-buffer-monad

https://github.com/dcastro/safe-buffer-monad

haskell haskell-library monad monad-transformers

Last synced: 26 days ago
JSON representation

• Host: GitHub
• URL: https://github.com/dcastro/safe-buffer-monad
• Owner: dcastro
• License: bsd-3-clause
• Created: 2018-05-25T16:30:30.000Z (over 6 years ago)
• Default Branch: master
• Last Pushed: 2018-06-19T19:57:33.000Z (over 6 years ago)
• Last Synced: 2024-09-27T16:36:26.635Z (about 1 month ago)
• Topics: haskell, haskell-library, monad, monad-transformers
• Language: Haskell
• Homepage: http://hackage.haskell.org/package/safe-buffer-monad
• Size: 22.5 KB
• Stars: 1
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# safe-buffer-monad

A monadic buffer resilient to exceptions.

The `SafeBufferMonad` typeclass models a buffer that you can write things to. If an exception is thrown,

you'll still be able to proccess the contents of the buffer up to the point where the computation was interrupted.

```haskell

class Monad m => SafeBufferMonad s m | m -> s where

  readBuffer   :: m s

  writeBuffer  :: s -> m ()

  clearBuffer  :: m s

  modifyBuffer :: (s -> s) -> m ()

```

The buffer can be run using one of these 6 functions:

* `runBuffer` / `runBufferConcurrently`

* `tryRunBuffer` / `tryRunBufferConcurrently`

* `execBuffer` / `execBufferConcurrently`

```haskell

{-# LANGUAGE FlexibleContexts #-}

import SafeBuffer

import Data.List (intercalate)

go :: (SafeBufferMonad [String] m, MonadIO m) => m String

go = do

  writeBuffer ["line 1"]

  writeBuffer ["line 2"]

  liftIO $ putStrLn "brace for impact!"

  liftIO $ throwIO $ userError "boom"

  writeBuffer ["line 3"]

  pure "done!"

main = runBuffer (appendFile "log.txt" . intercalate "\n") go

```

```plain

λ> main

brace for impact!

*** Exception: user error (boom)

λ> :! tail log.txt

line 1

line 2

```