#include <iostream>
#include <cmath>
using namespace std;
class Point
{
public:
    Point(int xx=0,int yy=0)
    {
        x=xx;
        y=yy;
    }
    Point(Point &p);//就是利用Point p来给其赋初值
    int getX() {return x;}
    int getY() {return y;}
private:
    int x,y;
};

Point::Point(Point &p)
{
    x=p.x;
    y=p.y;
    cout << "Calling the copy constructor of Point " << endl;
}

//类的组合
class Line
{
public:
    Line(Point xp1,Point xp2);
    Line(Line &1);
    double getLen() {return len;}
private:
    Point p1,p2;
    double len;
};

//组合类的构造函数
Line::Line(Point xp1,Point xp2):p1(xp1),p2(xp2)
{
    cout << "Calling constructor of Line" << endl;
    double x=static_cast<double>(p1.getX()-p2.getX());
    double y=static_cast<double>(p1.getY()-p2.getY());
    len=sqrt(x*x+y*y);
}

//组合类的复制构造函数
Line::Line(Line &1):p1(1.p1),p2(1.p2)
{
    cout << "Calling the copy constructor of Line " << endl;
    len=1.len;
}

//主函数
int main()
{
    Point myp1(1,1),myp2(4,5);
    Line line(myp1,myp2);
    Line line2(line);
    cout << "The length of the line is: ";
    cout << line .getLen() << endl;
    cout << "The length of the line2 is:";
    cout << line2.getLen() << endl;
    return 0;
}
怎么有一个浮点后缀常熟的错误提醒？？？
求大神解释

Line类里面对len成员变量并没有给出定义

？？有定义len啊。double len？？

我说的是你没有给它赋予实际意义，你只是定义的这个变量，但没指明它表示什么

我猜你想用它表示程度，但你并没有赋予它边长值

#include <iostream>
#include <cmath>
using namespace std;
class Point
{
public:
    Point(int xx=0,int yy=0)
    {
        x=xx;
        y=yy;
    }
    Point(Point &p);//就是利用Point p来给其赋初值
    int getX() {return x;}
    int getY() {return y;}
private:
    int x,y;
};

Point::Point(Point &p)
{
    x=p.x;
    y=p.y;
    cout << "Calling the copy constructor of Point " << endl;
}

//类的组合
class Line
{
public:
    Line(Point xp1,Point xp2);
    Line(Line &l);
    double getLen() {return len;}
private:
    Point p1,p2;
    double len;
};

//组合类的构造函数
Line::Line(Point xp1,Point xp2):p1(xp1),p2(xp2)
{
    cout << "Calling constructor of Line" << endl;
    double x=static_cast<double>(p1.getX()-p2.getX());
    double y=static_cast<double>(p1.getY()-p2.getY());
    len=sqrt(x*x+y*y);
}

//组合类的复制构造函数
Line::Line (Line &l): p1(l.p1), p2(l.p2)
{
    cout << "Calling the copy constructor of Line " << endl;
    len=l.len;
}

//主函数
int main()
{
    Point myp1(1,1),myp2(4,5);
    Line line(myp1,myp2);
    Line line2(line);
    cout << "The length of the line is: ";
    cout << line .getLen() << endl;
    cout << "The length of the line2 is:";
    cout << line2.getLen() << endl;
    return 0;
}
不过我的和这个书本提供代码，一样的，为啥他的就能够运行？？
谢谢了，大神

这里面len有没有复制也没有默认的值应该输出乱码，你再好好看看是不是少了一个函数

//组合类的复制构造函数
Line::Line(Line &1):p1(1.p1),p2(1.p2)
{
    cout << "Calling the copy constructor of Line " << endl;
    len=1.len;
}
把它的后一条语句改成len=1.getlen();试试

#include <iostream>
#include <cmath>
using namespace std;
class Point
{
public:
    Point(int xx=0,int yy=0)
    {
        x=xx;
        y=yy;
    }
    Point(Point &p);//就是利用Point p来给其赋初值
    int getX() {return x;}
    int getY() {return y;}
private:
    int x,y;
};

Point::Point(Point &p)
{
    x=p.x;
    y=p.y;
    cout << "Calling the copy constructor of Point " << endl;
}

//类的组合
class Line
{
public:
    Line(Point xp1,Point xp2);
    Line(Line &l);
    double getLen() {return len;}
private:
    Point p1,p2;
    double len;
};

//组合类的构造函数
Line::Line(Point xp1,Point xp2):p1(xp1),p2(xp2)
{
    cout << "Calling constructor of Line" << endl;
    double x=static_cast<double>(p1.getX()-p2.getX());
    double y=static_cast<double>(p1.getY()-p2.getY());
    len=sqrt(x*x+y*y);
}

//组合类的复制构造函数
Line::Line(Line &l):p1(l.p1),p2(l.p2)//不是1，是小写L
{
    cout << "Calling the copy constructor of Line " << endl;
    len=l.len;
}

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

没发现你改了哪