main.cpp

#include <stdio.h>
#include <assert.h>
#include <typeinfo>

namespace game {
	class Object { virtual void _(){}; };

	class Asteroid : public Object {};
	class Ship     : public Object {};
	class Bullet   : public Object {};

	class Physics {
	public:
		#define collide(at, bt, block)         \
			{                                  \
				at* a = dynamic_cast<at*>(x);  \
				bt* b = dynamic_cast<bt*>(y);  \
				if(a && b) block               \
			}

		bool collides(Object *x, Object *y){
			collide(Asteroid, Asteroid, {
				printf("asteroid with asteroid\n");
				return a == b;
			});

			collide(Ship, Ship, {
				printf("ship with ship\n");
				return a == b;
			});

			collide(Ship, Asteroid, {
				printf("ship with asteroid\n");
				return false;
			});

			// you can assert(false), if you don't have a match
			// you can generate the type-switch which fails at compile time
			// or use some template trickery to not use generation
			return false;
		};

		#undef collide
	};
}

int main(int argc, char const *argv[])
{
	auto physics  = new game::Physics();
	auto asteroid = new game::Asteroid();
	auto ship     = new game::Ship();
	auto bullet   = new game::Bullet();

	physics->collides(asteroid, asteroid);
	physics->collides(asteroid, ship);
	physics->collides(asteroid, bullet);
	physics->collides(ship,     asteroid);
	physics->collides(ship,     ship);
	physics->collides(ship,     bullet);
	physics->collides(bullet,   asteroid);
	physics->collides(bullet,   ship);
	physics->collides(bullet,   bullet);

	return 0;
}