c++第三次实验—作业

短命女 2022-07-26 11:24 271阅读 0赞

项目2：友元函数

#include<iostream>
    #include<cmath>
    
    using namespace std;
    class CPoint
    {
    private:
        double x;  // 横坐标
        double y;  // 纵坐标
     public:
        CPoint(double xx=0,double yy=0):x(xx),y(yy){}
    	double jvli1(CPoint a);
    	friend double jvli2(CPoint a,CPoint b);
    	double getx(){return x;}
    	double gety(){return y;}
    };
    
    double CPoint::jvli1(CPoint a)
    {
    	double dx=a.x-x;
    	double dy=a.y-y;
    	return sqrt(dy*dy+dx*dx);
    }
    double  jvli2(CPoint a,CPoint b)
    {
    	double dx=a.x-b.x;
    	double dy=a.y-b.y;
    	return sqrt(dx*dx+dy*dy);
    }
    double  jvli3(CPoint a,CPoint b)
    {
    	double dy,dx;
    	dx=a.getx()-b.getx();
    	dy=a.gety()-b.gety();
    	return sqrt(dx*dx+dy*dy);
    }
    int main( )
    {
    	CPoint p1(0,0),p2(1,1);
    	cout<<" 成员函数调用："<<p1.jvli1(p2)<<endl;
    	cout<<" 友元函数调用："<<jvli2(p1,p2)<<endl;
    	cout<<" 普通函数调用："<<jvli3(p1,p2)<<endl;
    
    	return 0;
    
    }

项目3：友元类

#include<iostream>
    #include<cmath>
    
    using namespace std;
    class Date; //对Date类的提前引用声明
    class Time
    {
    public:
        Time(int h,int m,int s):hour(h),minute(m),sec(s){}
        void add_a_second(Date &);  //增加1秒，1秒后可能会到了下一天，乃到下一月、下一年
        void display(Date &);  //显示时间，格式：月/日/年 时:分:秒
    private:
        int hour;
        int minute;
        int sec;
    };
    
    
    class Date
    {
    public:
        Date(int m,int d,int y):month(m),day(d),year(y){}
        friend class Time; //Time为Date的友元类
    private:
        int month;
        int day;
        int year;
    };
    void Time::add_a_second(Date &d)
    {
    	sec++;
    	if(sec>=60)
    	{
    		minute++;
    		sec=0;
    		if(minute>=60)
    		{
    			hour++;
    			minute=0;
    			if(hour>=24)
    			{
    				d.day++;
    				hour =0;
    				if(d.day>=31)
    				{
    					d.month++;
    					d.day=1;
    					if(d.month>12)
    					{
    						d.year++;
    						d.month=1;
    					}
    				}
    				else if(d.day>=30&&(d.month==4||d.month==6||d.month==9||d.month==11))
    				{
    					d.day=1;
    					d.month++;
    				}
    				else if(d.month==2)
    				{
    					if(d.day>=29)
    					{
    						d.day=1;
    						d.month++;
    					}
    					else if(d.day>=28&&(d.year%4!=0||(d.year%100==0&&d.year%400!=0)))
    					{
    						d.day=1;
    						d.month++;
    					}
    				}
    			}
    
    		}
    	}
    
    }
    void Time::display(Date &d)
    {
    	cout<<d.month<<"/"<<d.day<<"/"<<d.year<<"  "<<hour<<":"<<minute<<":"<<sec<<endl;
    }
    int main( )
    {
        Time t1(23,59,32);
        Date d1(2,28,2013);   //测试时，再试试Date d1(12,31,2013)会如何
        for(int i=0; i<=100; i++)
        {
            t1.add_a_second(d1);
            t1.display(d1);
        }
        return 0;
    }
    //下面定义两个类中的成员函数，要求不得再增加成员函数
    //注意体会在Time的成员函数中可以调用Date类的私有数据成员