Is Boost.Tuple compatible with C++0x variadic templates?

Question

I was playing around with variadic templates (gcc 4.5) and hit this problem :

template 
boost::tuple
my_make_tuple(Arg         


        

Answer 1

It doesn't seem to like expanding Args... to T1, T2, T3, ..., T9 as Boost has it.

As a workaround, use constructs that don't require this expansion:

#include 

template 
auto my_make_tuple(Args... args) -> decltype(boost::make_tuple(args...))
{
   return {args...};
}

int main (void)
{
    boost::tuple t = my_make_tuple(8, 'c');
}

---

Another option might be to do the expanding manually, seeing that boost::tuple supports up to 10 arguments.

#include 

template  struct nth_argument;

template 
struct nth_argument
{
    typedef typename nth_argument::type type;
};

template 
struct nth_argument<0, Default, T, Args...>
{
    typedef T type;
};

template 
struct nth_argument
{
    typedef Default type;
};

template 
struct tuple_from_var_template
{
    typedef boost::tuple<
        typename nth_argument<0, boost::tuples::null_type, Args...>::type,
        typename nth_argument<1, boost::tuples::null_type, Args...>::type,
        typename nth_argument<2, boost::tuples::null_type, Args...>::type,
        typename nth_argument<3, boost::tuples::null_type, Args...>::type,
        typename nth_argument<4, boost::tuples::null_type, Args...>::type,
        typename nth_argument<5, boost::tuples::null_type, Args...>::type,
        typename nth_argument<6, boost::tuples::null_type, Args...>::type,
        typename nth_argument<7, boost::tuples::null_type, Args...>::type,
        typename nth_argument<8, boost::tuples::null_type, Args...>::type,
        typename nth_argument<9, boost::tuples::null_type, Args...>::type
    > type;
};

template 
typename tuple_from_var_template::type my_make_tuple(Args... args)
{
   return typename tuple_from_var_template::type(args...);
}

int main (void)
{
    boost::tuple t = my_make_tuple(8, 'c');
}