Re: [boost] [msm]how to distinguish region ids?

Subject: Re: [boost] [msm]how to distinguish region ids?
From: Christophe Henry (christophe.j.henry_at_[hidden])
Date: 2011-06-21 15:09:20

> Hello,
>
> On Boost.Msm 1.46.1,
> When I use explicit entries and entry pseudo states, I have to provide a 
> template argument "region id".
> http://www.boost.org/doc/libs/1_46_1/libs/msm/doc/HTML/ch03s02.html#d0e930
>
> But I couldn't find documents about numbering policy of region id.
> I also check the example below.
> http://www.boost.org/doc/libs/1_46_1/libs/msm/doc/HTML/examples/DirectEntryTutorial.cpp
> The example passes the region id 0 and 1.
> I'd like to know how to decide which region is 0(or1).
>
> Am I missing something?
>
> Thanks,
> Takatoshi

Hi,

The region ids are numbered in the order of the initial_state typedef:

typedef boost::mpl::vector<Start1,Start2> initial_state;

Start1 will be the initial state of the first region (id 0), Start2 the 
initial state of the second region (id 1).
Alternatively, you can omit the id and let MSM build a graph using mpl_graph 
and find this out for you (which will work if your pseudo entry is somehow 
connected to the initial state). Please note however that there is a 
compile-time cost for this.

HTH,
Christophe