[Boost-users] [call_traits] Having trouble with call traits combined with type deduction

'Afternoon, I have a quick question on call traits and template argument deduction. I want to use call_traits' value_type and param_type to deduce a signature like double desired_result(double const& x); given an argument of type double. Is there any way to get type deduction working on a snippet like lousy_attempt (below) to produce my desired_result? #include template<typename Scalar> typename boost::call_traits<Scalar>::value_type lousy_attempt(typename boost::call_traits<Scalar>::param_type x) { return x; } int main() { double y = 5; // Works... lousy_attempt<double>(y); // "No matching function call to lousy_attempt(double&)" lousy_attempt(y); return 0; } Thanks in advance, Rhys