第12章 多态性与虚函数习题解答.docVIP

第12章 多态性与虚函数 习题参考答案 1、在例12.1程序的基础上作一些修改。声明Point(点)类派生出Circle(圆)类，再由Circle类派生出Cylinder(圆柱体)类。将类的声明部分分别作为3个头文件，对它们的成员函数的声明部分分别作为3个源文件(.cpp文件)，在主函数中用“#include”命令把它们包含进来，形成一个完整的程序，并上机运行。 //习题12.1中的cylinder.h头文件 //CYLINDER.H #include circle.h class Cylinder:public Circle {public: Cylinder (float x=0,float y=0,float r=0,float h=0); void setHeight(float); float getHeight() const; float area() const; float volume() const; friend ostream operator(ostream,const Cylinder); protected: float height; }; //习题12.1中的cylinder.cpp文件 //CYLINDER.CPP Cylinder::Cylinder(float a,float b,float r,float h):Circle(a,b,r),height(h){} void Cylinder::setHeight(float h){height=h;} float Cylinder::getHeight() const {return height;} float Cylinder::area() const { return 2*Circle::area()+2*3.14159*radius*height;} float Cylinder::volume() const {return Circle::area()*height;} ostream operator(ostream output,const Cylinder cy) {outputCenter=[cy.x,cy.y], r=cy.radius, h=cy.height \narea=cy.area(), volume=cy.volume()endl; return output; } //习题12.1中的point.h头文件 //POINT.H class Point {public: Point(float=0,float=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; }; //习题12.1中的point.cpp文件 //POINT.CPP 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; } //习题12.1中的circle.h文件 //CIRCLE.H #include point.h 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 ); protected: float radius; }; //习题12.1中的circle.cpp文件 //CIRCLE.CPP //#include iostream.h Circle::Circle(float a,float b,float r):Point(a,b),radius(r){} void Circle::setRadius(float r) {radius=r;} float Circle::getRadius() const {return radius