RE: [boost] Re: overloads-20050207.tar.gz

From: Alexander Nasonov (alnsn_at_[hidden])
Date: 2005-02-12 04:25:03

David Abrahams wrote:
> "Alexander Nasonov" <alnsn_at_[hidden]> writes:
>
> > struct Fsm
> > {
> >     Running operator()( id<1>, Passive, EvActivate ) const;
> >     Stopped operator()( id<2>, Running, EvStartStop ) const;
> >     Running operator()( id<3>, Stopped, EvStartStop ) const;
> >     Stopped operator()( id<4>, Active, EvReset ) const;
> >     // ...
> > };
>
> It's not directly relevant to your overloads component, but I'm very
> curious as to why you want to use _types_ to represent states.  It
> seems counter-productive because of course types are static, and
> states are, well, stateful.  Don't you end up wasting time and code
> translating between states and types?

That's possible. If your automata is essentially value-based (for example,
FSM for searching subsrings in a string) then it's better to use something
else. But, in a modern world, type identity plays an important role too.
For example, if someone is developing FSM silimar to mine where each event
has additional params (eg, EvActive may have priority), what would he/she
prefer, to invent his/her own protocol to transmit event code and event
specific params or to use existing technology like CORBA and to send
objects?

PS Mine code is implementation of UML diagram from boost::fsm tutorial by
Andreas Huber:
http://boost-sandbox.sourceforge.net/libs/fsm/doc/tutorial.html
--
Alexander