[boost] Re: [fsm] Why exit actions must not fail

From: Andreas Huber (ah2003_at_[hidden])
Date: 2004-05-30 18:34:56

David Abrahams wrote:
> "Andreas Huber" <ah2003_at_[hidden]> writes:
>
>> David Abrahams wrote:
>>>> Yes, but only at the cost of making the current interface (and
>>>> implementation) more complex (we'd need to have at least a separate
>>>> exit() function, right?).
>>>
>>> No.  At the moment we're just talking about whether A1 is justified.
>>> Whether or not exit actions should use destructors is a separate
>>> question.
>>
>> Is it? In the current design the state machine object owns the state
>> objects (it does so for good reasons). How can you destruct the state
>> machine object without destructing the state objects (and thus
>> inevitably also exiting them and terminating the state machine as a
>> result)?
>
> You're still collapsing separate concepts.

The current implementation does. I don't think I did with the above
reasoning.

> Conceptually, state (machine) destruction is independent of
> state machine termination.

Yes, conceptually. However, since in the current implementation the state
machine destructor will inevitably destruct all the state objects, it is
also inevitable that they are all exited (which is equivalent to terminating
the state machine). That's why I said that I'd need to change the state
interface to separate state machine termination (which calls exit() on all
states and destructs them afterwards) from destruction (which only destructs
the states).

Regards,

Andreas