``` template class F> struct call_me {}; template struct maybe; template struct more; int main() { call_me a; // ok call_me b; // error } ``` I understand why `call_me ` 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)?

``` template class F> struct call_me {}; template struct maybe; template struct more; template class F> struct just_one { template using tmpl = F ; }; int main() { call_me a; call_me ::tmpl> b; } ``` Not exactly equivalent, but maybe close enough.

Fixed number of template arguments from a variadic template

c++, c++11, templates, variadic-templates

Solution

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.

Problem

``` 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)?

Original source