c++ - Is it possible to loop over template parameters? -

i have kind of code :

template <typename t1,           typename t2 = void,           typename t3 = void,           typename t4 = void,           typename t5 = void> std::set<std::type_info const*> myclass<t1,t2,t3,t4,t5>::get_types() {     std::set<std::type_info const*> t;     t.push_back(&typeid(t1));     if(typeid(t2) != typeid(void))       t.push_back(&typeid(t2));     else       return;     if(typeid(t3) != typeid(void))       t.push_back(&typeid(t3));     else       return;     if(typeid(t4) != typeid(void))       t.push_back(&typeid(t4));     else       return;     if(typeid(t5) != typeid(void))       t.push_back(&typeid(t5));     else       return; } 

is there way make loop on templates types t2 t5 avoid redundant code ?

note: don't use c++11. use boost.

yes can boost mpl using facilities of boost::mpl::vector , boost::mpl::for_each example below:

live demo

code:

#include <iostream> #include <typeinfo> #include <vector> #include <boost/mpl/vector.hpp> #include <boost/mpl/for_each.hpp> #include <boost/mpl/placeholders.hpp>  template <typename t> struct wrap {};  class bar {   std::vector<std::type_info const*> &types; public:   bar(std::vector<std::type_info const*> &types_) : types(types_) {}   template<typename t> void operator()(wrap<t>) const {      if(typeid(t) != typeid(void)) types.push_back(&typeid(t));   } };  template<typename t1, typename t2 = void, typename t3 = void, typename t4 = void, typename t5 = void> struct foo {   std::vector<std::type_info const*> get_types() const {     std::vector<std::type_info const*> out;     boost::mpl::for_each<boost::mpl::vector<t1, t2, t3, t4, t5>, wrap<boost::mpl::placeholders::_1> >(bar(out));     return out;   } };  int main() {  foo<int, long, double> foo;  std::vector<std::type_info const*> types = foo.get_types();   for(int i(0), isz(types.size()); < isz; ++i) {    std::cout << types[i]->name() << std::endl;      } }