I want to call a macro with some arguments depending on the result of boost::mpl::eval_if
(or a similar function) that could give how many template arguments are not empty. Say we have some pseudocode like the following:
struct EmptyType { };
template<class arg1=EmptyType, class arg2=EmptyType, class arg3=EmptyType>
class my_class
{
eval_if<is_not_same<arg1, EmptyType>, FILL_MY_CLASS_DEFINE(1)> else
eval_if<is_not_same<arg2, EmptyType>, FILL_MY_CLASS_DEFINE(2)> else
eval_if<is_not_same<arg3, EmptyType>, FILL_MY_CLASS_DEFINE(3)>;
};
I am trying to fill my class with some content depending on how many arguments are EmptyType
. I wonder how such thing can be done in C++03 via Boost.MPL/Preprocessor or some other Boost library?