#include<iostream>
#include <cmath>
using namespace std;
class Point
{
public:
Point(int xx=0,int yy=0) { X=xx;Y=yy;}
Point(Point &p);
int GetX() {return X;}
int GetY() {return Y;}
private:
int X,Y;
};
Point::Point(Point &p)
{
X=p.X;
Y=p.Y;
cout<<"point 拷贝构造"<<X<<Y<<endl;
}

class Line
{
public:
Line(Point xp1,Point xp2);
Line(Line &L);
double GtLen() {return len;}
private:
Point p1,p2;
double len;
};
Line::Line(Point xp1,Point xp2)1(xp1),p2(xp2)
{
cout<<"Line 构造"<<endl;
double x=double(p1.GetX()-p2.GetX());
double y=double(p1.GetY()-p2.GetY());
len=sqrt(x*x+y*y);
}

Line::Line(Line &L)1(L.p1),p2(L.p2)
{
cout<<"Line 拷贝构造"<<endl;
len=L.len;
}

int main()
{
Point myp1(1,1),myp2(4,5);
Line line(myp1,myp2);
Line line2(line);
cout<<"length of the line is:";
cout<<line.GtLen()<<endl;
cout<<"length of the line2 is:";
cout<<line2.GtLen()<<endl;
return 0;
}




代码如上,运行显示:
point 拷贝构造45
point 拷贝构造11
point 拷贝构造11
point 拷贝构造45
Line 构造
point 拷贝构造11
point 拷贝构造45
Line 拷贝构造
length of the line is:5
length of the line2 is:5
Press any key to continue


我的疑问是
1 为什么point的拷贝构造函数会先 执行myp2然后是myp1
2 为什么有四个拷贝构造函数呢?
我debug了一下,发现在执行
Line line(myp1,myp2);的时候 会先拷贝构造myp2(4,5),然后拷贝构造myp1(1,1),然后构造line,并拷贝构造myp1和myp2. 我主要是前两个点的拷贝构造不理解
谢谢大家的帮助啊