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
template<typename... Types>
class Tuple;
template<typename T>
class TupleElt
{
T value;
public:
TupleElt() = default;
template<typename U>
TupleElt(U&& other) : value(std::forward<U>(other) { }
T& get() { return value; }
T const& get() const { return value; }
};
// recursive case:
template<typename Head, typename... Tail>
class Tuple<Head, Tail...>
: private TupleElt<Head>, private Tuple<Tail...>
{
public:
Head& getHead() {
// potentially ambiguous
return static_cast<TupleElt<Head> *>(this)->get();
}
Head const& getHead() const {
// potentially ambiguous
return static_cast<TupleElt<Head> const*>(this)->get();
}
Tuple<Tail...>& getTail() { return *this; }
Tuple<Tail...> const& getTail() const { return *this; }
};
// basis case:
template<>
class Tuple<> {
// no storage required
};