Re: [boost] [msm] Version 2.0 available

Subject: Re: [boost] [msm] Version 2.0 available
From: Andreas Huber (ahd6974-spamboostorgtrap_at_[hidden])
Date: 2009-11-12 12:16:41

>>:-) You won't get any flames from me. Yes, I don't agree with some of the
>>points in MsmSession_Handout.pdf (e.g. 2.4, a user in his right mind would
>>put Stopped, Open, Paused and Playing into an outer CDLoaded state and 
>>then
>>only say if (state_downcast<const CDLoaded *> != 0)).
>
> True, it is a possible solution. But 1) you don't always want to
> refactor your state machine and

But you'd have to refactor an equivalent MSM Machine too (you'd need to 
introduce the flag), right?

> 2) sometimes you can't.
> For example, to take the example in the Statechart
> documentation(http://www.boost.org/doc/libs/1_40_0/libs/statechart/doc/tutorial.html#StateQueries),
>
> if ( ( state_downcast< const NumLockOff * >() != 0 ) &&
>        ( state_downcast< const CapsLockOff * >() != 0 ) &&
>        ( state_downcast< const ScrollLockOff * >() != 0 ) )
>
> could have been replaced by
> if(fsm.is_flag_active<IsOffState,Active::Flag_AND>()). And in this
> case I don't see a working refactoring solution.

Agreed. The example is somewhat far-fetched, but such queries are needed 
sometimes (mostly to work around the limitation that statechart doesn't 
offer join bars).

Regards,

-- 
Andreas Huber
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