#include <iostream>
using namespace std;
 
class IComparable {
	public: 
		virtual bool Equal(const IComparable&) = 0;
 
		typedef int IsComparable;
};
 
class Foo : public IComparable {
	public: bool Equal(const IComparable&) {
		return true;
	}
};
 
template <typename Comparable>
void compare(const Comparable& cmp, const Comparable& cmp2) {
	typedef typename Comparable::IsComparable Guard;
}
 
int main() {
	Foo f;
	compare(f, f);
	//compare(10, 20);
	return 0;
}

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