Hello Joel, Tuesday, December 06, 2005, 8:30:32 PM, you wrote: JR> Assuming I typed events like that I think I would need a typed sink JR> for them as well. I only have one sink for the events and that is my JR> message queue. i don't understand you. remember that i'm not native English speaker :) JR> I expect users to want User X, User Y, User Z within JR> the same module and that's why I used Dynamic. if you can define all these datatags (X, Y and Z) in one type then you can use pattern matching: data UserEvent = X ... | Y ... | Z ... if not - then can't. of course, you can use this "subtyping trick" several times, but it is not very interesting: data Event a = ... | User a data UserEvent1 a = X ... | User2 a data UserEvent2 a = Y ... | User3 a send chan (User $ User2 $ Y) -- type of expression inside brackets is "Event (UserEvent1 (UserEvent2 a))", where a is unspecified or you can define data Event a b c = ... | User1 a | User2 b | User3 c but this is also bad :( you can also use classes, but Dynamic actually does the same, and this gives you no ability to do pattern-matching -- Best regards, Bulat mailto:bulatz@HotPOP.com