The interview covers proposed metaprogramming features in upcoming versions of C++. In particular, it demonstrates metaclass as a way for users to define new ki

The interview covers proposed metaprogramming features in upcoming versions of C++. In particular, it demonstrates metaclass as a way for users to define new kinds of types, instead of relying solely on class/struct/union/enum. For example, Java has an interface, in which methods are declared but not defined. The proposal for metaclass gives a demonstration of what an interface in C++ could look like: interface Shape { int area() const; void scale_by(double factor); }; Instead of changing the compiler to allow for new interface keyword, we can create a metaclass: // the dollar sign ($) prefix indicates reflection and metaprogramming $class interface { // the constexpr indicates compile-time execution constexpr { // raise an error if there are data members compiler.require($interface.variables().empty(), "interfaces may not contain data"); // loop over all functions for (auto f : $interface.functions()) { // raise an error if move/copy functions are present compiler.require(!f.is_copy() && !f.is_move(), "interfaces may not copy or move"); // function must be public if (!f.has_access()) f.make_public(); compiler.require(f.is_public(), "interface functions must be public"); // function must be virtual f.make_pure_virtual(); } } // add a destructor virtual ~interface() noexcept { } }; Thus I can create a new kind of type directly in my code. This can be part of a library for downstream users without ever changing the compiler. See the full proposal here: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0707r2.pdf http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p070...