C++ Primer Plus

Unpacking the Packs

But how can the function access the contents of these packs? There is no indexing feature. That is, you can’t use something like Args[2] to access the third type in a pack. Instead, you can unpack the pack by placing the ellipsis to the right of the function parameter pack name. For example, consider the following flawed code:

template<typename... Args>    // Args is a template parameter packvoid show_list1(Args... args) // args is a function parameter pack{    show_list1(args...); // passes unpacked args to show_list1()}

What does this mean, and why is it flawed? Suppose we have this function call:

show_list1(5,'L',0.5);

The call packs the values 5, 'L', and 0.5 into args. Within the function, the call

show_list1(args...); ...