SFINAE: Check whether the concatenation of two variadic packs is the same as one pack

Question

Is there a way to check whether the concatenation of two variadic argument packs is the same as a third variadic argument pack.

template<typename... Args>
struct ClassOne
{
}

template<typename... Args>
struct ClassTwo
{
}

template<typename... Args>
struct ClassThree
{
}

template<typename... PackA, typename... PackB, typename... PackC>
void foo(ClassOne<PackA...>, ClassTwo<PackB...>, ClassThree<PackC...>)
{
}

I would like foo to only be enabled if PackA... = PackB..., PackC...

Answer 1

Rather straightforward...

template <typename ...>
struct pack{};

template<typename... PackA, typename... PackB, typename... PackC,
  typename = typename std::enable_if
     <std::is_same<pack<PackA...>, 
                   pack<PackB..., PackC...>>::value
     >::type>
void foo(ClassOne<PackA...>, ClassTwo<PackB...>, ClassThree<PackC...>)
{
}