Partial specialization of variadic template member function

Question

I'm struggling with specializations of member functions when they are templated using variadic template.

The following example specializes a whole class and it works fine:

template<typename... Args>
class C;

template<class T, typename... Args>
class C<T, Args...> { };

template<>
class C<> { };

int main() {
    C<int, double> c{};
}

The following one does not, even though the idea behind it is exactly the same of the one above:

class F {
    template<typename... Args>
    void f();
};

template<class T, typename... Args>
void F::f<T, Args...>() { }

int main() {
}

I'm getting the following error and I don't understand what it's due to:

main.cpp:7:23: error: non-type partial specialization ‘f<T, Args ...>’ is not allowed
 void F::f<T, Args...>() { }
                       ^
main.cpp:7:6: error: prototype for ‘void F::f()’ does not match any in class ‘F’
 void F::f<T, Args...>() { }
      ^
main.cpp:3:10: error: candidate is: template<class ... Args> void F::f()
     void f();
          ^

Is there some constraints I'm not aware of when specializing function template?

G++ version is: g++ (Debian 5.2.1-23) 5.2.1 20151028

EDIT

By the way, the actual problem I'm getting from the real code is:

non-class, non-variable partial specialization ‘executeCommand<T, Args ...>’ is not allowed

Anyway, the reduced example is similar to the real one. I hope the errors are not completely unrelated.

Answer 1

You cannot partially specialize function templates; only explicit specialization is allowed.

You can get pretty much the same effect using overloading, especially if you use concepts such as tag dispatching.