那里出错了呢？

harderror 2012-08-12 08:19:51



#include <iostream>

using namespace std;

class Point

{public:

        Point(float x=0,float y=0);

        void setPoint(float,float);

        float getX() const {return x;}

        float getY() const {return y;}

        friend ostream & operator<<(ostream &,const Point &);

protected:

          float x,y;

          };

Point::Point(float a,float b)

          {x=a;y=b;}

void Point::setPoint(float a,float b)

          {x=a;y=b;}

ostream & operator<<(ostream &output,const Point &p)

          {output<<"["<<p.x<<","<<p.y<<"]"<<endl;

          return output;}

          

int main()

{Point p(3.5,6.4);

cout<<"x="<<p.getX()<<",y="<<p.getY()<<endl;

p.setPoint(8.5,6.8);

cout<<"p(new):"<<p<<endl;

system("pause");

} 

class Circle:public Point

{public:

        Circle(float x=0,float y=0,float r=0);

        void setRadius(float);

        float getRadius() const;

        float area() const;

        friend ostream &operator<<(ostream &,const Circle &);

private:

        float radius;

      };

Circle::Circle(float a,float b,float r):Point(a,b),radius(r)

      {}

void Circle::setRadius(float r)

      {radius=r;}

float getRadius() const {return radius;}

float area() const

      {return 3.1415926*radius*radius;}

ostream &operator<<(ostream &output,const Circle &c)

      {output<<"Center=["<<c.x<<","<<c.y<<"],r="<<c.radius<<".area="<<c.area()<<endl;

      return output;

      }

int main()

{Circle c(3.5,6.4,5.2);

cout<<"original circle:\\nx="<<c.getX()<<",y="<<c.getY()<<",r="<<c.getRadius()<<",area="<<c.area()<<endl;

c.setRadius(7.5);

c.setPoint(5,5);

cout<<"new circle:\\n"<<c;

Point &pRef=c;

cout<<"pRef:"<<pRef;

return 0;

}

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harderror 2012-08-14

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[Quote=引用 2 楼的回复:]

2个main函数
[/Quote]

呵呵，新手！！

startservice 2012-08-12

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2个main函数；
另外发现即使去掉一个main函数，在VC6.0下还是会报错，友元问题。

IVERS0N 2012-08-12

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2个main函数

漫步者、 2012-08-12

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#include <iostream>

using namespace std;

class Point

{

public:

        Point(float x=0,float y=0);

        void setPoint(float,float);

        float getX() const {return x;}

        float getY() const {return y;}

        friend ostream & operator<<(ostream &,const Point &);

protected:

          float x,y;

          };



Point::Point(float a,float b)//最好与定义类的参数一致

          {x=a;y=b;}

void Point::setPoint(float a,float b)

          {x=a;y=b;}

ostream & operator<<(ostream &output,const Point &p)

          {output<<"["<<p.x<<","<<p.y<<"]"<<endl;

          return output;}





class Circle:public Point

{

public:

        Circle(float x=0,float y=0,float r=0);

        void setRadius(float);

        float getRadius() const;

        float area() const;

        friend ostream &operator<<(ostream &,const Circle &);

private:

        float radius;

};



Circle::Circle(float a,float b,float r):Point(a,b),radius(r)

      {}

void Circle::setRadius(float r)

      {

		  radius=r;

}

float Circle::getRadius() const //这里写掉了Circle::，它是成员函数

{

	return radius;

}

float Circle::area() const//同理

      {return 3.1415926*radius*radius;}

ostream &operator<<(ostream &output,const Circle &c)

      {output<<"Center=["<<c.x<<","<<c.y<<"],r="<<c.radius<<".area="<<c.area()<<endl;

      return output;

    



}

int main()

{Circle c(3.5,6.4,5.2);

cout<<"original circle:\\nx="<<c.getX()<<",y="<<c.getY()<<",r="<<c.getRadius()<<",area="<<c.area()<<endl;

c.setRadius(7.5);

c.setPoint(5,5);

cout<<"new circle:\\n"<<c;

Point &pRef=c;

cout<<"pRef:"<<pRef;

return 0;

}

//还有一个地方是，你的程序中出现了2个main函数，你要去掉一个。