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Subject: Re: [boost] [msm]exit pseudo state and event
From: Takatoshi Kondo (kondo_at_[hidden])
Date: 2011-07-12 19:31:00

On Mon, 11 Jul 2011 21:31:43 +0200
"Christophe Henry" <christophe.j.henry_at_[hidden]> wrote:

> > The functor Not_ is suitable for "else".
> > But if we have much more guards, We have to use Or_ functor like this.
> > msme::Not_< msme::Or_< msme::Or_<Guard1, Guard2>, Guard3> >
> >
> > Off the top of my head, how about the functor Else_ below?
> > Else_ <Guard1, Guard2, Guard3, ... >
> For else, we can use the fact that msm tries guards from the bottom of the
> table to the top:
> // else clause
> Row< state1, ev, state2, none, none>,
> // if clause
> Row< state1, ev, state2, none, Or_<...> >
> // more if clauses
> ...

This has 2 advantages and 1 disadvantage.

One is simple enough. The other is good performance.
It doesn't need evaluating the guard functor twice.
I was about to consider how to cache the functor's result.

As you might expect, the evaluating direction is opposite of my intuition.

Are there any reasons of this implementation?
Modifying to the opposite direction is easy?

> It's not UML-conform, but well ;-)
> HTH,
> Christophe


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