Re: [Boost-users] [statechart] forward_event()

Subject: Re: [Boost-users] [statechart] forward_event()
From: Commander Pirx (CmdPirx_at_[hidden])
Date: 2009-10-12 05:20:23

Hi all,

thanks for the help. I compiled the project with GCC. The behaviour is 
unchanged. Furthermore I'm not able to reproduce the behaviour in a 
simplified demo code. I've even tried to debug the statechart library and 
read the 
http://www.boost.org/doc/libs/1_40_0/libs/statechart/doc/reference.html#process_event 
documentation carefully. But I must honestly say, I have not quite 
understood. Thats why I have a simple question: Is it guaranteed that the 
innermost states are called first? If yes, I have a bug (hard to detect). If 
no, I have to rewrite my code.

Note: When working with the statechart libraries I got some ideas to improve 
the "usability". Think about it as a wishlist.

1. Debugging features, like in the Spirit Library. e.g. easy naming of 
states, tracing the event route, more debug output (verbose mode)
2. Calling the state constructor with an event. something like transit<S>( 
event );
3. A process_event() method that acceepts an intrusive pointer. Currently 
each event will be duplicated (clone()).
4. A thread safe scheduler. It's hard to use hundreds of instances of the 
asynchronous_state_machine because each instance needs a thread.  Correct me 
if I am wrong here.
5. Macros to define events, where all memebers are const. I've found that 
it's error prone to write it by hand again and again.
6. Thanks!

Pirx!

"Andreas Huber" <ahd6974-spamboostorgtrap_at_[hidden]> schrieb im Newsbeitrag 
news:hanjjh$aim$1_at_ger.gmane.org...
> Hi
>
>> I have a state [A] with three orthogonal substates [X,Y,Z]. The states 
>> [A] and [X] provide custom reactions for an event [E]. If processing 
>> event [E] the state machine calls first the custom reaction in [A]. This 
>> method returns with forward_event() ; After this the custom reaction in 
>> [A] is called again. And then custom reaction in [X] is called.
>>
>> This is a little cumbersome. Why is the custom reaction in [A] called 
>> twice?
>>
>> And why is the outermost state called first? It would be something easier 
>> to work vice versa. First the more "specialized" inner states could do 
>> there work and then the "generalized" outer states can do the everything 
>> else.
>
> This behavior is as designed, for an in-depth description please see:
>
> <http://www.boost.org/libs/statechart/doc/reference.html#process_event>
>
> Reaction search always starts with an *arbitrary* innermost state and then 
> first works its way outward. Only when the outermost state has been 
> reached is the next innermost state checked for a suitable reaction. This 
> behavior stems form the fact that all reactions defined in outer states 
> are "inherited" by their direct and indirect inner states, as mandated by 
> the UML standard.
>
> What are you trying to achieve? Maybe I can suggest a more suitable 
> implementation.
>
> HTH,
>
> -- 
> Andreas Huber
>
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