[evlan-devel] event driven programming / exceptions

[Bob I. <bo...@re...>]

I've pretty much read everything on the Evlan website, and I have a few 
questions..

The concepts document says:
 > The usual alternative is to use event-driven programming, where a 
single
 >  thread (or a small group of them) is notified whenever something 
happens
 >  that it needs to attend to.  This technique is much more scalable 
(provided
 >  the programmer doesn't make the mistake of using poorly-designed 
system
 > calls like select(2)), but is also much more difficult to write.  Many
 > programmers avoid event-driven programming because of the extra work
 > involved.  Evlan, however, is designed to make event-driven 
programming
 > easier.

I've done quite a bit of event driven programming myself, in C, ObjC 
and Python, and I've never seen a portable and efficient way around 
using the select call for async programming with file descriptors.  How 
do you plan to get around this limitation in Evlan?  Short of using a 
thread dedicated to sitting on select(), or polling (using a short or 
no timeout on select, if there is other processing to be done) I can't 
think of any way.  How do you plan to support timed events (sleep for a 
while, call this function later, etc.)?  What are your ideas for how 
the scheduler will work in Evlan, given that today's processors are 
basically serial?

Also I didn't see any mention of exceptions anywhere.  Do you plan to 
implement exceptions, or something functionally equivalent to them?

-bob