Need example of using boost::fusion::filter_if metafunction

Question

Given a boost::fusion::vector type, I want to filter out all the non-ref members to get a new type. For example this would transform boost::fusion::vector into boost::fusion::vector. I'm guessing the boost::fusion::filter_if meta function might be able to do this, but there's no example of its use in the documentation. Any suggestions would be appreciated.

Actually, there is an example here under **Print only pointers**: http://www.boost.org/doc/libs/1_61_0/libs/fusion/doc/html/fusion/quick_start.html — Adi Shavit, Aug 31 '16 at 12:41

score 0 · Answer 1 · answered Nov 18 '12 at 20:16

Something like this:

#include <iostream>
#include <boost/fusion/container/vector.hpp>
#include <boost/fusion/algorithm/transformation/filter_if.hpp>
#include <boost/fusion/include/at_c.hpp>
#include <boost/fusion/include/equal_to.hpp>
#include <boost/fusion/include/make_vector.hpp>
#include <boost/mpl/assert.hpp>

using namespace boost::fusion;

int main(void)
{
    int a = 10;
    double b = 11.;
    vector<int, int&, double, double&> vec(1, a, 13., b);

    if(filter_if<boost::mpl::not_<boost::is_reference<boost::mpl::_>>>(vec) == make_vector(1, 13.))
      std::cout << "MATCH" << std::endl;
}

Need example of using boost::fusion::filter_if metafunction

1 Answers1