Strong typedef / member functions on built-in types (C++17)

c++17-crtp-variadic-mixins.cpp

// Transcribed (with simple modifications and added comments) from _Fundamentals of Type-Dependent Code Reuse in C++_ presentation by Mark Isaacson at NDC 2015
template <typename T, template <typename> class... Mixins>
  struct Mixer : public Mixins< Mixer<T, Mixins...> >... {
    // N4477 Operator Dot (R2), on track for C++17
    T& operator.() { return value; }
  private:
    T value;
  };

template <typename T>
  struct HelloMixin {
    void print_hello() {
      using namespace std;
      cout << "hello\n"s;
    }
  };

using helloable_int = Mixer<int, HelloMixin>;

// …
auto x = helloable_int{};
auto y = x + 5;              // ← like an int here
x.print_hello();             // ← voodoo here