The following code example is taken from the book
C++ Templates - The Complete Guide, 2nd Edition
by David Vandevoorde, Nicolai M. Josuttis, and Douglas Gregor,
Addison-Wesley, 2017
© Copyright David Vandevoorde, Nicolai M. Josuttis, Douglas Gregor 2017
// determine whether the tuple is empty:
template<>
struct IsEmpty<Tuple<>> {
static constexpr bool value = true;
};
// extract front element:
template<typename Head, typename... Tail>
class FrontT<Tuple<Head, Tail...>> {
public:
using Type = Head;
};
// remove front element:
template<typename Head, typename... Tail>
class PopFrontT<Tuple<Head, Tail...>> {
public:
using Type = Tuple<Tail...>;
};
// add element to the front:
template<typename... Types, typename Element>
class PushFrontT<Tuple<Types...>, Element> {
public:
using Type = Tuple<Element, Types...>;
};
// add element to the back:
template<typename... Types, typename Element>
class PushBackT<Tuple<Types...>, Element> {
public:
using Type = Tuple<Types..., Element>;
};