Re: [Boost-users] [fusion] Introspection of fused objects?

Subject: Re: [Boost-users] [fusion] Introspection of fused objects?
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2010-02-25 21:26:10

AMDG

Rutger ter Borg wrote:
> Suppose I have a function object created on the basis of a sequence of fused 
> function objects, where I would like to do shuffle the call order on the 
> basis of some criterion.
>
> template< typename SeqOfFused >
> struct merge_fused {
>
>   merge_fused( SeqOfFused f ): m_functions( f ) {}
>
>   typedef void result_type;
>
>   template< int N, typename Seq >
>   void operator()( Seq& seq ) {
>
>     // normal dispatch call would be fusion::at_c<N>(m_functions)( seq );
>
>     if ( some case ) {
>        store seq for later use
>     } else {
>        call appropriate fused object with parts of stored stuff
>     }
>   }
>
>   SeqofFused m_functions;
>
>   // some state / memory specific to this group of fused objects
>   some_state m_state;
> };
>
> I'm doing a static cast to a superclass to get rid of the int N template 
> parameter, to make the merge_fused look exactly like a fused function 
> object. This works fine.
>   

What are you casting to a superclass?

> Storing stuff is what my question is about: is there any way to know the 
> type of Seq from its Fused counterpart? Looking at the code, the answer is 
> no, but perhaps there exists introspection code in fusion which I am unaware 
> of?
>   

What is the "Fused Counterpart" of Seq.

> One solution would be to simply use static casting based on Seq in 
> operator(), but then my question would be: is that safe?
>   

Is Seq always that same type? It sounds dangerous, but I don't really
understand what you want to do.

In Christ,
Steven Watanabe