Why is this variadic function ambiguous?

Question

This is related to my earlier post. I\'d like to know why one attempted solution didn\'t work.

template              /* A */
size_t num_         


        

Answer 1

Apropos the usefulness/uselessness of free variadic function templates: the usual use case for these is to have a variadic function parameter list, in which case a regular overload for the empty case will do just fine:

size_t num_args()
{
    return 0;
}

template  /* B */
size_t num_args (H h, T... t)
{
    return 1 + num_args(t...);
}

---

EDIT:

As far as I can see, the following abuse of enable_if ought to work as a solution to your original question:

#include 

// Only select this overload in the empty case 
template 
typename std::enable_if<(sizeof...(T) == 0), size_t>::type
num_args() 
{ 
    return 0;
}

template 
size_t
num_args() 
{
    return 1 + num_args();
}

(Edit2: Reversed the order of the overloads to make the code actually compile)