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
#include "findindexof.hpp"
template<typename T, typename... Types>
class VariantChoice {
using Derived = Variant<Types...>;
Derived& getDerived() { return *static_cast<Derived*>(this); }
Derived const& getDerived() const {
return *static_cast<Derived const*>(this);
}
protected:
// compute the discriminator to be used for this type
constexpr static unsigned Discriminator =
FindIndexOfT<Typelist<Types...>, T>::value + 1;
public:
VariantChoice() { }
VariantChoice(T const& value); // see variantchoiceinit.hpp
VariantChoice(T&& value); // see variantchoiceinit.hpp
bool destroy(); // see variantchoicedestroy.hpp
Derived& operator= (T const& value); // see variantchoiceassign.hpp
Derived& operator= (T&& value); // see variantchoiceassign.hpp
};