Question

template <template <typename> class F> struct call_me {};
template <typename T> struct maybe;
template <typename... T> struct more;

int main()
{
  call_me<maybe> a; // ok
  call_me<more> b;  // error
}

I understand why call_me<more> fails. But I want to make it work.

Is there a workaround that doesn’t involve changing call_me (or add an specialization to it)?

Answer 1

template <template <typename> class F> struct call_me {};
template <typename T> struct maybe;
template <typename... T> struct more;
template <template <class...> class F> struct just_one {
  template <class A> using tmpl = F<A>;
};

int main()
{
  call_me<maybe> a; 
  call_me<just_one<more>::tmpl> b;  
}

Not exactly equivalent, but maybe close enough.