[boost] Re: Please, comment design decision of simple FSM

From: Andreas Huber (ah2003_at_[hidden])
Date: 2004-09-14 17:32:09

David Abrahams wrote:
> "Andreas Huber" <ah2003_at_[hidden]> writes:
>
>> Alexander Nasonov wrote:
>>>> Andreas Huber wrote:
>>>>> This all looks very nice. Is it possible to use this scheme with
>>>>> polymorphic states, as follows:
>>>>
>>>> See attachment. It is slow but demonstrates the idea and can be
>>>> improved later.
>>
>> Wow! So simple and yet powerful. It naturally supports nested states
>> and polymorphic events. I guess this could quite easily be developed
>> into a fast & lightweight boost::fsm alternative. Cool!
>
> It's very close to the organization of the MPL FSM samples I have
> posted in the past...

Yep, I had noticed that. What I like better about Alexander's approach 
is that the transition table is implemented with ordinary C++ what makes 
it quite a bit more expressive than the MPL collections you used in your 
examples. Don't get me wrong, I personally love MPL, but I've found that 
the average programmer is easily scared away with even very simple MPL 
constructs.

> only there's no dumb O(N) for_each dispatching
> in my samples: they're O(1).

Unless I'm missing something one could easily modify Alexander's code to 
be O(1) too...?

Regards,

Andreas