Restrict variadic template arguments

Question

Can we restrict variadic template arguments to a certain type? I.e., achieve something like this (not real C++ of course):

struct X {};

auto foo(X... args)
         


        

Answer 1

What about the following solution ?

--- EDIT --- Improved following suggestion from bolov and Jarod42 (thanks!)

#include 

template 
auto foo(Args... args) = delete;

auto foo ()
 { return 0; }

template 
auto foo (int i, Args ... args)
 { return i + foo(args...); }

int main () 
 {
   std::cout << foo(1, 2, 3, 4) << std::endl;  // compile because all args are int
   //std::cout << foo(1, 2L, 3, 4) << std::endl; // error because 2L is long

   return 0;
 }

You can declare foo() to receive all types of arguments (Args ... args) but (recursively) implement it only for one type (int in this example).