hi, I am new to boost. I have a class that takes in 10 template parameters (std::size_t N1 to N10). I need to create a mpl::list_c using N1 to N10. I have an empty mpl::list_c (acc). I plan to check each of N1 to N10 and if the value > 0 i will insert into the list. Can someone please tell me how i could do this. I have tried for one N1 alone using an mpl::if_ but that doest seem to work template struct access_list{ typedef mpl::list_c<int> acc; //I tried for N1 this way but this does not word typedef mpl::if_< mpl::bool_, typename mpl::push_back::type, mpl::false_ >::type type; }; --------------------------------------------------------------------------------------------------------- Suresh