[Boost-users] How to deduce (possibly void) return type of member function?

Subject: [Boost-users] How to deduce (possibly void) return type of member function?
From: Terry Golubiewski (tjgolubi_at_[hidden])
Date: 2010-05-22 10:53:58

If I have a class...

struct X {
  int f(double x);
  void f(int y);
};

... and a template Y that wants to deduce the return-type of some member 
functions of T...

template<class T>
struct Y {
  typedef typename what_goes_here<T>::type f_double_return_type;
  typedef typename what_goes here<T>::type f_int_return_type;
};

I"ve tried using...

typedef  BOOST_TYPEOF_TPL(static_cast<X*>(0)->f(double(0))) f_double_type; 
// this works

... but ...

typedef BOOST_TYPEOF_TPL(static_cast<X*>(0)->f(int(0)) f_int_type;  // does 
not work for "void"

Of course, I wouldn't know which one returns "void" or not ahead of time.

terry