读几个小程序了解c++：Part 04（多态）

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本文介绍了一个使用C++实现多态性的示例。通过基类Student和派生类Undergraduate展示如何通过虚函数实现多态行为。在主函数中通过指向基类的指针调用虚函数，演示了多态的特性。

#include "iostream"
using namespace std;
///多态是指不同子类间的同名函数表现形式不同
///实现多态可以让变量根据类型选择合适的同名函数


class Student {
public:
	Student(string n, int a, int h, int w);
	Student(){}
	void set_(string n, int a, int h, int w);
	virtual double study();      ///虚函数  函数（返回值类型、形参类型顺序、个数）必须完全一样才能实现多态
	///virtual void study()=0; ///纯虚函数,抽象类
	virtual ~Student();


private:
    char *l;
	string name;
	int age;
	int height;
	int weight;
};
Student::~Student(){delete l;cout<<"Delete Student\n"<<endl;}
Student::Student(string n, int a, int h, int w) {set_(n, a, h, w);}
void Student::set_(string n, int a, int h, int w) {name=n, age=a, height=h, weight=w;}
double Student::study() {cout << "Student gz.\n" << endl;return 0.2;}


class Undergraduate:public Student{
public:
    double study();
    ~Undergraduate();
private:
    char *r;
    double score;
};
Undergraduate::~Undergraduate(){delete r;cout<<"Delete Undergraduate.\n"<<endl;}
double Undergraduate::study(){cout<<"Undergraduate gz.\n"<<endl;return 1;}
int main(){
    Undergraduate a;
    Student b;




    Student *sp;
    sp=&a;
    sp->study();


    //sp=&b;
    //sp->study();
    return 0;
}