How can I have multiple parameter packs in a variadic template?

Question

Function one() accepts one parameter pack. Function two() accepts two. Each pack is constrained to be wrapped in types A and B. Why is it

Answer 1

Here is another way to have several parameters packs using template template parameters:

#include 

template 
struct foo {};

template < typename... Types1, template  class T
         , typename... Types2, template  class V
         , typename U >
void
bar(const T&, const V&, const U& u)
{
  std::cout << sizeof...(Types1) << std::endl;
  std::cout << sizeof...(Types2) << std::endl;
  std::cout << u << std::endl;
}

int
main()
{
  foo f1;
  foo f2;
  bar(f1, f2, 9);
  return 0;
}