[Boost-users] enable_if operator+ exists

Is there a way to use enable_if so that one specialization gets selected if operator+ exists between two types, and another specialization if operator+ does not exist? For example: template<class A, class B, boost::enable_if<operator_plus_exists<A,B>

::type* dummy = 0> void operator()(const A& a, const B& b) { std::cout << "a + b = " << (a + b) << std::endl; }

template<class A, class B, boost::disable_if<operator_plus_exists<A,B>

::type* dummy = 0> void operator()(const A& a, const B& b) { }

How would I implement the operator_plus_exists class?