Re: [Boost-users] [function] generalization of std::plus and std::multiplies with more than one argument type

21 Oct 2009

      alfC wrote:
...
thank you er and Mathias for your answers,
...
...
alfC wrote:
...
Does Boost have a generalization of std::plus and std::multiplies
(std_function.hpp)?
How about the boost::lambda arithmetic operators, possibly in  
combination with ll_static_cast<Tp>, and -if necessary- put the  
result in the functor wrapper boost::function
what is  "ll_static_cast<Tp>"? after that part I got lost.
the cast was in mind to allow for an argument that is convertible to but 
not necessarily equal to Tp.
...
but I need this generalization of multiplies as one of the default
parameter of a template, how would you pass a lambda expression as
template parameter?
Since you insist on a template parameter,

template
struct my_class{

    typedef function F;

    my_class() : f(G<Tp>::create()){}

    F f;
};

template<typename Tp>
struct default_factory{

     typedef BOOST_TYPEOF(
        lambda::_1 * lambda::_2
     ) result_;

     static result_ create(){ return lambda::_1 * lambda::_2; }

};

I did not even try to compile it, just an idea.
...
The reason I returned to my post is that today I found boost/mpl/
plus.hpp and boost/mpl/multiplies.hpp which seem to answer the first
part of my question (although not the syntactic sugar part).
Thank you,
Alfredo