Getting ready

The examples in this recipe are based on the variadic function template add() that we wrote in the previous recipe, Writing a function template with a variable number of arguments. That implementation is a left-folding operation. For simplicity, we present the function again:

    template <typename T> 
    T add(T value) 
    { 
      return value; 
    } 

    template <typename T, typename... Ts> 
    T add(T head, Ts... rest) 
    { 
      return head + add(rest...); 
    }