Re: [Boost-users] [statechart] completion event

From: Francisco Santos (fmnsantos_at_[hidden])
Date: 2007-07-27 06:28:15

Hi Andreas,

Don't have a solution yet, although I understand the problem you 
describe about the guard conditions over a completion transition. If I 
come up with an elegant solution I will post it in this newsgroup.

I have yet another question regarding events:
Can you create a hierarchy of events in such a way that Boost is able to 
  distinguish between the new subtypes?
Here is an example to clarify the question:

class AbstractEvent : public sc::event<AbstractEvent>{};
class EventA : public AbstractEvent{};
class EventB : public AbstractEvent{};

In this example, events EventA and EventB have the same type ID as 
AbstractEvent in Boost. Is there a way of giving EventA and EventB 
different type IDs, without inheriting directly from event< ... >?

Thank you,
Francisco Santos

Andreas Huber wrote:
> Hi Francisco
> 
>> Are completion transitions and events supported by the Statechart Boost
>> library?
> 
> No, they are not currently supported. You are the first to ask for them.
> 
> I did consider to add them but was unable to come up with a clean 
> implementation, see below.
> 
>> A completion transition is a transition without an explicit trigger, 
>> although it may have a guard defined.
> 
> IIRC, this was the main obstacle. If, when the first completion event is 
> generated, the guard is false, what does then happen? Will there be another 
> dispatch of such an event? If so, when or under what conditions?
> 
>> When all transition
>> and entry actions and activities in the currently active state are 
>> completed, a completion event instance is generated. This event
>> is the implicit trigger for a completion transition. The completion 
>> event is dispatched before any other queued events and has
>> no associated parameters. For instance, a completion transition 
>> emanating from a concurrent composite state will be taken
>> automatically as soon as all the concurrent regions have reached their 
>> final state.
>> If multiple completion transitions are defined for a state, then they 
>> should have mutually exclusive guard conditions.
> 
> Maybe you have better insight into how this should work?
> 
> Regards,
> 
> --
> Andreas Huber
> 
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