Re: [Boost-users] Dynamic function call question

Subject: Re: [Boost-users] Dynamic function call question
From: Ovanes Markarian (om_boost_at_[hidden])
Date: 2009-02-26 13:22:02

On Thu, Feb 26, 2009 at 6:53 PM, Perry, Daniel <PerryD_at_[hidden]> wrote:

> AMDG
>
> Perry, Daniel wrote:
> > I've been trying to design a function dispatch system and I was
> > wondering if the following is possible with the current boost
> libraries...
> >
> > I currently parse json data into an vector of variants, I would like
> > to be able to take those variants and invoke an arbitrary boost
> > function object with a consistent return type.
> >
> > Is it possible to determine the function argument types, get the typed
>
> > value from the proper index in the array of variants, and call the
> > function with arguments?
> >
> > This sounds like something the boost fusion library might be able to
> > do, but I can't find any example code using the library to see if this
>
> > is the right fit for the capabilities of the library or if what I'm
> > looking to do is not possible without tons of boiler plate.
>
> Is apply_visitor what you are looking for?
> http://www.boost.org/doc/html/boost/apply_visitor.html
>
> In Christ,
> Steven Watanabe
>
>
> Steven,
>
> 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?
>
> Regards,
>
> Daniel Perry

Seems, to me you are looking for multi-methods, which might become the part
of the next standard.

I can only find this document describing the approach, but there is no
status on it:

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2216.pdf

>From this document you might also be able to derive you solution.

Ovanes