Re: [Boost-users] [statechart] Working with state history - compilation errors

From: Andreas Huber (ahd6974-spamgroupstrap_at_[hidden])
Date: 2005-10-17 08:11:55

Hi John

<john.wismar <at> autozone.com> writes:
> I'm playing with the statechart library,
> in conjunction with Boost 1.33 and VC 7.1. Â I'm having trouble using
> the state history functionality; I can't get it to compile, even taking
> into account the useful static assertions that ought to be helping me.
> Â Can someone suggest what I might be missing?Here's a boiled down sample: 
there
> are 2 top-level states, StateA and StateB. Â Event2 transitions between
> them. Â When in StateA, Event1 transitions between 2 sub-states, StateA1
> and StateA2. Â When transitioning from StateB to StateA, I want to
> use StateA's history to determine which of StateA1 and Stae2 become active.

I'm very sorry for the late answer, but I missed your post back in September 
because it was sent in reply to an unrelated post (Boost Graph Library).

Mick's analysis of the problem is correct. When you make a transition to 
history then you must specify the *default* *state* that is entered in case 
the history has never been saved before. The *outer* *state* of the default 
state must then pass the appropriate has_xxx_history.

Note that this is very much in line with the UML notation. A transition to 
history always goes to a H disc first and from that H disc you have another 
arrow to the default state. The state containing the H disc is said to be the 
one "having history".

>  From reading the tutorial, references, and sample code, it looks
> like this should work:
[example snipped]

I checked the docs and I can't find any examples that display the wrong syntax 
you used. A pointer would be appreciated.

HTH & Regards,

-- 
Andreas Huber 
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