Re: [boost] Re: Proposal: cartesian_product algorithm and a finitestatemachinetemplate library

From: Terje Slettebø (tslettebo_at_[hidden])
Date: 2002-10-30 15:07:20

>From: "Marc Jacobs" <marcja_at_[hidden]>
>
> A common strategy for using this kind of state machine is raise an event
> before doing some work to see if the work is allowed in the current state.
> Example:
>
> void BusinessObject::turnPowerOn() {
>     try {
>         context::raise( fsmtl::event< fsm::poweron >() );
>         // do work for turn the power on
>     }
>     catch( fsmtl::exception & e )
>     { ... }
>
> If the transition is not permitted given the current state and event, an
> exception is thrown and no work is performed. Whether the exception is
> rethrown, not caught, or translated into a different kind of exception is
up
> to the library user.

Exception handling may be expensive. Perhaps it could be good to provide a
query, to determine if an operation may be performed.

Regards,

Terje