gistfile1.hpp

#include <iostream>

// header
class Test {
public:
	void func();

private:
	class util;
	friend class util;

	int member1;
	int member2;
};


// source
class Test::util : public Test {
public:
	int benri_func() const;
};

int Test::util::benri_func() const
{
	return member1 + member2;
}

void Test::func()
{
	member1 = 1;
	member2 = 2;
	int val = static_cast<util*>(this)->benri_func();
	std::cout << val << std::endl;    // 3
}

int main(void)
{
	Test t;
	t.func();
}