What are some examples of using STM in Haskell?

Can you give me some examples of using STM in Haskell?

Sure! Haskell's Software Transactional Memory (STM) allows for composable memory transactions. One example is using TVar to manage shared state.

How do I create a TVar and use it in a transaction?

You can create a TVar using newTVarIO and then use atomically to perform transactions. For example:

import Control.Concurrent.STM

main = do
    counter <- newTVarIO 0
    atomically $ modifyTVar' counter (+1)

What happens if a transaction fails?

If a transaction fails, it will automatically retry until it succeeds or is aborted. This ensures consistency.

Can you explain how to handle multiple TVars in a transaction?

Certainly! You can read and write to multiple TVars within a single atomically block. Just ensure you handle potential deadlocks.