c++ - How to check presence of static const member with SFINAE -

suppose have several structs fields optional:

struct param1 {     static const bool x = true; };  struct param2 { }; 

and want write template function

template <class paramtype> bool returnparam(); 

which should return paramtype::x if static field x exists, otherwise should return false

i suppose sfinae magic should help.

constraint

i using msvc 2010, cannot use of c++11 features.

this code works perfectly:

template<typename t, typename memberptrgetter> struct has_member_impl { private:     template<typename u> static char test(typename memberptrgetter::template type<u>*);     template<typename u> static int test(...);  public:     static const bool value = sizeof(test<t>(0)) == sizeof(char); };   template <typename t, typename memberptrgetter> struct has_member: public std::integral_constant<bool, has_member_impl<t, memberptrgetter>::value> { };  struct staticmembergetter {     template <typename t, const bool = t::x>     struct type     {     }; };  struct param1 {     static const bool x = true; };  struct param2 { };  template <typename param, typename t = void>  struct extractparam {     static const bool x = false; };  template <typename param> struct extractparam<param, std::true_type> {     static const bool x = param::x; };  template <typename param> bool returnparam() {     return extractparam<param, has_member<param, staticmembergetter>>::x; }