Dear Haskellers, After a long absence I again have the chance to follow the discussions in the forums. And now I would like to express my personal opinion. A lot of attention is paid to the way of realizing the multithreading in CGA. I totally agree that the choice of concrete abstraction for multithreading is a little bit out of the CGA standard. The callback functions are simple and effective way of realizing the event handling. This mechanism doesn�t require but also doesn�t exclude the usage of threads. The stream-based library can be developed later on top of callback functions. In order to realize multithreading all library primitives should be thread safe. Primitives whose execution require a long period of time (i.e. the primitives that start event-loop or directly/indirectly execute the callback functions in Haskell) should not block the execution of the concurrent threads. The way of realizing it depends on the used compiler. For the future versions of GHC probably the best way will be by using �threadsafe� foreign calls, but for Hugs maybe the �yield� primitive. That�s why I propose not to specify the exact way of multithreading. AS for the realization, it can be done in a different way for the different combinations compiler/toolkit. Another point that I noticed is the way of registering/unregistering of the event handlers. Under Windows all events are passed to the function handler even if it ignores them. Under GTK the event is passed only if there is a registered event handler. All libraries based on X have similar design because this allows minimizing of the traffic between the application and the X server. It is a disadvantage of the GTK based Port library where all event handlers are automatically registered even if they are ignored by the Haskell program. It is not difficult to correct this, but we have to bear it in mind when making the standard. Summary: - CGA should use callback functions for event handling - All primitives should be thread safe - Calling whoever of the primitives should not block the concurrent threads. An exception can be done only for the primitives who are executed in a very short constant time - For each event there should be two functions: register and unregister I am under the impression that there is a consensus of all points mentioned above but they have to be specified in the standard. In this context I would like to ask whether there are any additions to the document that Axel wrote. Best wishes, Krasimir __________________________________________________ Do you Yahoo!? Yahoo! Web Hosting - establish your business online http://webhosting.yahoo.com