Class Drawable

example/injection.cpp:16–22

namespace te = boost::te;

struct Drawable : te::poly<Drawable> {
  using te::poly<Drawable>::poly;

  void draw(std::ostream &out) const {
    te::call([](auto const &self, auto &out) { self.draw(out); }, *this, out);
  }
};

struct Square {
  void draw(std::ostream &out) const { out << "Square"; }