Re: [Haskell-cafe] Can you do everything without shared-memory concurrency?

On 10 Sep 2008, at 20:28, Ryan Ingram wrote:

On Wed, Sep 10, 2008 at 2:55 AM, Maarten Hazewinkel wrote:

...

[on transaction failures in databases and STM]

This seems to be a bit too much F.U.D. for STM. As long as you avoid unsafeIOToSTM (which you really should; that function is far more evil than unsafePerformIO), the only failure case for current Haskell STM is starvation; some thread will always be making progress and you do not have to explicitly handle failure.

This is absolutely guaranteed by the semantics of STM: no effects are visible from a retrying transaction--it just runs again from the start. You don't have to write "proper error handling" code for transactional updates failing.

Thanks for the clarification Ryan. As a hobbyist I haven't actually used STM, so I was grouping it with databases as the only transactional system I am directly familiar with. I suppose I could have guessed that the Haskell community would come up with something that's a class better than a normal shared database. Regards, Maarten Hazewinkel