On Monday, April 25, 2011 06:39:14 PM Christophe Henry wrote:
> Hi Thomas,
>
> Sorry to come back to the subject so late, I didn't manage before :(
>
> > If you want to use it as a transform you need the evaluator with an
> > appropriate action that does the desired transform... here is an
> > example:
> >
> > struct BuildEventPlusGuard
> > : proto::when<
> > proto::subscript<proto::terminal<event_tag>,
> > phoenix::meta_grammar >,
> > TempRow<none,proto::_left,none,none,
> > phoenix::evaluator(proto::_right, some_cool_action())>()
> > >
> > {};
> >
> > Now, some_cool_action can do the transform that BuildGuards was doing.
>
> Hmmm, I get a compiler error, which was expected (would be too easy
> otherwise ;- ) ), but the error is surprising. The error is that
> phoenix::evaluator seems to believe some_cool_action should be a
> random access fusion sequence (expects an environment?).
You are right ... slippery on my side ... evaluator expects a context, which is
a tuple containing the environment and the actions: http://goo.gl/24fU9
> Anyway, I am hoping not to write any cool transform but simply save
> the type of the phoenix expression so that I can re-create an actor
> later. If I need to rewrite differently what BuildGuards was doing, I
> gain little. I would like phoenix to do the grammar parsing and
> building of actor.
It does ... just pass on proto::_right and it should be good:
struct BuildEventPlusGuard
: proto::when<
proto::subscript<
proto::terminal<event_tag>
, phoenix::meta_grammar // match the phoenix actor
>
, TempRow<
none
, proto::_left
, none
, none
, proto::_right // Pass the type along. which is a phoenix actor.
>(proto::_right) // Pass the object along. Which is the actor (1)
>
{};
(1): Here you can work around the thing with the possibly uninitialized stuff.
Just copy the phoenix actor (should be cheap, if not optimized away completely).
> Thanks,
> Christophe
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