How can I handle errors in Haskell's STM?

How can I handle errors in Haskell's STM?

In Haskell's Software Transactional Memory (STM), you can handle errors using the retry function or by using catchSTM to catch exceptions.

Can you give me an example of using catchSTM?

Sure! Here's a simple example:

import Control.Concurrent.STM
import Control.Exception (catch)

mySTMFunction :: STM ()
mySTMFunction = do
    -- some STM operations
    return ()

main :: IO ()
main = atomically (mySTMFunction `catch` handleError)
  where
    handleError :: SomeException -> STM ()
    handleError e = putStrLn $ "Error occurred: " ++ show e

What about using retry for error handling?

retry is used to pause the transaction until a condition is met. For example:

import Control.Concurrent.STM

myTransaction :: STM ()
myTransaction = do
    value <- readTVar myTVar
    if value < 0 then retry else return value