I'm using boost::variant in the following manner struct Visitor : boost::static_visitor<> { void operator()(int &i) const { i = 1; } }; boost::variant<int, char> var = 0; boost::apply_visitor(Visitor(), 0); I'm trying to get the program to compile if the variant takes on the guise of an int (because I've implemented void operator()(int &i) const, but not compile if I make the variant take the guise of a char e.g. boost::variant<int, char> var = 'a'; because I've not implemented the void operator()(char &c) const Can anyone think of a way of doing this, maybe using SFINAE (Substitution Failure Is Not An Error) I'm thinking of doing something along the lines of : template <typename T> struct SetObj; template <> struct SetObj<int> { void operator()(int &obj) const { obj = 1; } } struct Visitor : boost::static_visitor<> { template <typename T> void operator()(T& obj) const { SetObj<T>()(obj); } }; But not sure how to take it to the next level to get the desired behaviour. _________________________________________________________________ Have more than one Hotmail account? Link them together to easily access both http://clk.atdmt.com/UKM/go/186394591/direct/01/