Re: [Boost-users] [fusion] proposal BOOST_FUSION_ADAPT_FUNCTION, BOOST_FUSION_DEFINE_FUNCTION, etc

Subject: Re: [Boost-users] [fusion] proposal BOOST_FUSION_ADAPT_FUNCTION, BOOST_FUSION_DEFINE_FUNCTION, etc
From: alfC (alfredo.correa_at_[hidden])
Date: 2010-10-15 01:41:49

On Oct 14, 10:30 pm, OvermindDL1 <overmind..._at_[hidden]> wrote:
> On Thu, Oct 14, 2010 at 11:09 PM, alfC <alfredo.cor..._at_[hidden]> wrote:
> > Hi,
>
> >  I am using Boost.Fusion lately. Sometimes one has a function with
> > several parameters,
>
> > int f(double d , int i , std::string s){
> >  ...bla bla ...
> > }
>
> > the logic of the program says that sometimes that same funcion will be
> > called by generic code and in such case it is better if "f" where
> > defined as taking a fusion::vector as argument.
>
> > int f(fusion::vector<double, int, std::string>) // another function,
> > could be an overload even
>
> > since there is only one why to define this adaptor function, e.g.
> > int f(fusion::vector<double, int, std::string> x){
> >  return f(at_c<0>(x), at_c<1>(x), at_c<2>(x));\
> > }
>
> > and it is pretty mechanical. I was wondering if it would be a good
> > idea to have, with consistency with the  BOOST_FUSION_ADAPT_STRUCT,
> > something called BOOST_FUSION_ADAPT_FUNCTION
>
> > BOOST_FUSION_ADAPT_FUNCTION(
> >    int, f,
> >    double,
> >    int,
> >    std::string
> > )
> > (or something like that)
> > that defines the second / fusion-compatible version of f.
>
> > It could be even a
>
> > BOOST_FUSION_DEFINE_FUNCTION(
> >    int, f,
> >    (double, d),
> >    (int, i),
> >    (std::string, s),
> >    ( ... code using variables d, i, s or at_key<d_>, at_key<i_>,
> > at_key<s_> ...  )
> > )
>
> > that defines simultaneously the raw-C function, f(double, int, string)
> > *and* the fusion friendly version f(vector<...>).
> > I could probably program these macro for specific cases but not a
> > general one since I don't know enough macro syntax to make it work.
>
> > Do you think it is a good idea or it is already doable with existing
> > Fusion features?
>
> It should already be doable, given example:
>   // include fusion here
>
>   int f(double d , int i , std::string s){
>     ...bla bla ...
>   }
>
>   int main(void) {
>     boost::fusion::vector<double,int,std::string myVec(3.14, 42,
> "Hello World!");
>     return boost::fusion::invoke(&f, myVec);
>   }

cool.
one question:  does it work for member functions as well?

Thank you.

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