How to identify types in boost fusion vector

Question

How would one go about identifying the types inside a boost::fusion vector?

e.g.

fusion::vector<int, double, string> v;

then something that would let me identify v[0] as being type int, v[1] as type double and v[2] as type string.

Thanks.

Answer 1

In order to extract an element from a boost::fusion::vector you need to use boost::fusion::at_c, like this:

boost::fusion::vector<int, std::string> v(1, "hello");
std::cout << boost::fusion::at_c<0>(v) << std::endl; // prints 1

The type at position N is:

boost::fusion::result_of::at_c<boost::fusion::vector<int, std::string>, 1>::type