I'm not sure I want to follow WWRD all the way. I do want events, for example mouse clicks (for which there doesn't seem to be any logical behavior representation). As you note the pull-based approach does a lot more work in those cases than seems necessary. Events are indispensable for practically all applications, even those that have continuous output, so leaving them out would be no option. I only did so for Elerea to be able to quickly get a working system running, so I can actually experiment with application-side design. But yeah, it can't be used for serious purposes without some support for events.

In any case, what I'm discussing in that report is mostly centered on the continuous-time values, so I'm more concerned with what we call behaviors. The question is how to model memory-full operations with point-wise operations. I think it would help if you tried to solve more specific problems first and see what common structure you can factor out from the solutions. It's easy to get into a dead end if you go for the big picture right away.

Right. You'll agree that it would be nice to have a general approach? How will that work? That's what I'd like to find out. And I do hope you'll manage to find a useful result. My intuition says, however, that looking for a sensible interface between events and behaviours is more fruitful than trying to unify these two notions. The reason is the difference in TCMs, as noted previously.

report. I'd like things to be unified, so maybe playing with the idea of a total function to 'Maybe a' for events is the right direction. I think this was already explored by some FRP incarnations, but I don't recall what came out of it. Yes, that's the Yampa way. The problem is that in this case you'll need an awkward operator to refer to 'the time of last defined point'.

But isn't Lucid Synchrone essentially discrete-timed? Also, events shouldn't be semantically constrained to multiples of some basic clock, they are defined over continuous time. Of course, it's more like a possible model for operational semantics (I know you're interested in denotation, but inspiration can come from anywhere). I just thought that clock calculus might be an interesting topic to throw into the hat.

Gergely -- http://www.fastmail.fm - Email service worth paying for. Try it for free