From: Andreas Huber (ah2003_at_[hidden])
Date: 2004-05-30 17:32:43
David Abrahams wrote:
>> I think a foundation for a decision is not flimsy when the behavior
>> in question has proved to be useful in practice. So far nobody, who
>> seems to have experience with non-trivial FSMs, has doubted that it
>> is useful to terminate a state machine when it is destructed (my
>> assumption A1).
>
> I don't doubt that it's often useful. I also think it is surely
> sometimes highly undesirable.
I'd be interested in examples.
> If you remove A1, the "useful" behavior
> is trivial to achieve without transforming the FSM, so it seems that a
> design without A1 is both more flexible and more orthogonal.
Removing A1 means complicating the interface (see my other post regarding
exit()).
>> BTW, as pointed out by someone else the user *does*
>> have a choice. If she happens to have an exit action that she'd
>> rather not have executed upon destruction then she can always
>> transform the machine part in question such that her action is
>> executed as part of a transition action instead (I would consider it
>> a design error not to do so).
>
> Why?
>
>> Every Moore machine (an FSM that has only entry and exit actions)
>> can be transformed to a Mealy machine (an FSM that has only
>> transition actions) and vice versa.
>
> Why require a transformation when it's not neccessary?
Because I very much believe that such a transformation is necessary only in
very few cases (I've never encountered one) and I don't want to complicate
the interface and potentially also pessimize the implementation for all
users just because of those few cases.
Regards,
Andreas