Re: Event based language, does it exist?

Per Olesen wrote:


> I'm trying to find a language which is based solely on events


I'm not sure if this is the meaning you are looking for, but there are
hardware description languages based upon events (or at least with
events as one datatype). For example in Verilog, you can declare
events and once the events are declared one can wait on and trigger
them. Moreover, every assignment to a variable can be (and to some
extent is) described in terms of a series of events and when they are
scheduled and what events happen as a side-effect of that assignment.


The events in Verilog are, of course, derived from Simula which is a
"discrete event simulation language". I only vaguely remember Simula,
so I won't expand on its use of events.


Another view on events are the transitions in finite state machines.
In an FSM, every input is an "event" and the result of the execution
of the machine causes a state transition and also the generation of an
output (which can be considered to be an "event"). As a result, if
you looked internally at the sources to Yacc++, the lexer is described
in terms of events (not in terms of "characters"). You might want to
look into Statecharts if that is the direction you are interested in
pursuing.


Following a parallel to that there is a an "event" language for
describing window actions that is part of one of the X toolkits. It
is called something like UML or UDL, but it is not the Unified
Modelling Language of OO circles. The concept behind this language
(as I understand it) is that windowing events (and the systems
appropriate reaction to them) can be described using FSM's.


Hope this helps,
- -Chris


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Chris Clark Internet : compres@world.std.com
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