Hi, I have a problem regarding the static visitor of boost::variant. there is a variant and a mpl vector: variant<A1,A2,A3> var; typedef mpl::vector<B1,B2,B3> B_types; the variant and the vector have the same number of types, but not the same types. I need to "visit" the element of the variant, and access the B_types element at the same position as the element of the variant: struct visitor : static_visitor<void>{ template<class A> void operator()(A a) const{ typedef typename mpl::at_c<B_types,var.which()>::type B; //error } }; so if var.which() == 1, I need a typedef of type B2. obviously the code above doesn't work because which() is a runtime function. but the value of which() is known statically at this point (that's the point of visitation). is there a way to access it, with boost::variant visitors? I like neither of the solutions I can come up with: 1. write my own visitation pattern that not only instantiates the visitor with the variant type but also with the vector type. 2. convert the variant to template<class A,class B> struct A_holder{ typedef B B_type; A value; }; variant<A_holder<A1,B1>,A_holder<A2,B2>,A_holder<A3,B3> > var; 3. do a seperate "visition" of the mpl vector inside the variant visitor: struct visitor : static_visitor<void>{ template<class A> void operator()(A a) const{ switch(var.which()){ case... case... } } }; is there a better way to do this?