运算符重载（一）

重载为友员函数。

#include <iostream>
using namespace std;
class Clock
{
private:
	int s;
	int m;
	int h;
public:
	void display();
	Clock(Clock &);
	Clock(int, int, int);
	friend Clock operator+(int, Clock&);
	friend Clock operator+(Clock&, int);
};
void Clock::display()
{
	cout << h << ":" << m << ":" << s << endl;
}
Clock::Clock(Clock&c)
{
	m = c.m;
	s = c.s;
	h = c.h;
}
Clock::Clock(int x, int y, int z)
{
	h = x;
	m = y;
	s = z;
}

Clock operator +(int x,Clock&c)
{
	Clock clk = c;
	clk.h += c.h;
	clk.h %= 24;
	if (clk.h < 0)
		clk.h += 24;
	return clk;
}

Clock operator+(Clock&c, int x)
{
	Clock clk = c;
	clk.h += c.h;
	clk.h %= 24;
	if (clk.h < 0)
		clk.h += 24;
	return clk;

}
void main()
{
	Clock one(5, 30, 0);
	one.display();
	Clock two = one + 4;
	two.display();
	Clock three = 100 + two;
	three.display();
	getchar();
}