Re: [Boost-users] Dynamic function call question

Subject: Re: [Boost-users] Dynamic function call question
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2009-02-26 13:44:52

AMDG

Perry, Daniel wrote:
> No I was aware of the visitors.  I am thinking more along the lines of 
>
> template< Signature>
> void Execute( vector<variant> args, function<Signature> & Fun )
> {
> 	fusion::vector< parameter_types<Signature>::type > typed_args(
> magic_happens_here(args));
> 	fusion::invoke_procedure(Fun, typed_args); 
> }
>
> What can I do to make the magic happen?
>   

So the function has a fixed signature?

You'll need to adapt a vector to the fusion interface.
The easiest way it to convert it to a boost::array (which is a fusion 
sequence)
and use transform (untested).

struct variant_get {
    template<class Sig>
    struct result {
        typedef typename boost::mpl::at_c<parameter_types<Sig> >::type type;
    };
    template<class Arg, class Type>
    Type operator(const Arg& arg, const Type& type) { 
return(boost::get<Type>(arg)); }
};

template<class Signature>
void Execute(const vector<variant>& args, const function<Signature>& Fun) {
    typedef typename parameter_types<Signature>::type param_types;
    boost::array<variant,boost::mpl::size<param_types>::value> as_array;
    typename fusion::as_vector<param_types>::type 
typed_args(boost::fusion::transform(as_array, param_types, variant_get()));
}

In Christ,
Steven Watanabe