The Template pack index is going to make
meta-template variadics much easier.
Usually this is prone to cludges like converting
parameters to structs or filtering them with functions holding the pack.
template <typename... T>
constexpr auto first_plus_last(T... values) -> T...[0] {
return T...[0](values...[0] + values...[sizeof...(values)-1]);
}
1. typename...
2. sizeof...
3. values...
4. T... representing multiple parameters in the formal parameter list.
5. T... for the type of the pack (supporting T...[0], the new feature).
I wonder why it's T...[0] and not just T[0]? In parameter lists you need the distinction between "T", a single parameter of pack type, and "T...", multiple parameters supplied from the pack. But I don't see a similar need in an expression.