On Mon, Mar 27, 2006 at 09:36:28AM +0100, Simon Marlow wrote:
On 26 March 2006 03:44, Ross Paterson wrote:
[...] the key point is that a Haskell' module that does not use concurrency, but is thread-safe, ought to work with non-concurrent implementations too.
To make that work, we'd need two interfaces: * one for applications that make use of concurrency. This would be unavailable on some implementations. * one for thread-safe use of state. This would be available on all implementations, and authors not requiring concurrency would be encouraged to use it for maximum portability.
Sure, I think this is a point on which we're all agreed.
The portable interface could be Control.Concurrent.MVar, perhaps.
As Malcolm pointed out, using MVars requires some care, even if you were just aiming to be thread-safe. Packaged things like atomicModifyIORef are safe, but awkward, and need extra stuff to handle multiple variables. How about STM (minus retry/orElse) and TVars as the portable interface? They're trivial for a single-threaded implementation, and provide a comfortable interface for everyone.