Concept checker

check_concept.cc

// sfinae test for has ThisFunc() method
template <typename T>
class has_this_func {
  typedef char one[1];
  typedef char two[2];
  template <typename U> static one test(decltype(&U::ThisFunc());  // could also be *U::Routing() for pointer to ThisFunc
// the above gets masked out as sfinae will choose two
  template <typename U) static two test(...);
 public:
  static bool const value = sizeof(test<T>(0)) == sizeof(one);
  // use has_this_func<T>::value as the test
};